Original Article
Below-Knee Prosthetic Bypass Is a Viable Option for Limb Salvage in Patients with Extensive Femoropopliteal Occlusive Disease
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Vasc Specialist Int (2023) 39:16
Published online June 29, 2023 https://doi.org/10.5758/vsi.230028
Copyright © The Korean Society for Vascular Surgery.
Abstract
Materials and Methods: This study included 37 consecutive patients who underwent BKPB with or without distal modification between 2010 and 2022. We further assessed the following treatment outcomes: primary patency (PP), secondary patency (SP), limb salvage (LS), and amputation-free survival (AFS) rates. The risk factors for PP were also examined.
Results: Most patients (n=31) were male. In 32 (86.5%) patients, BKPBs were performed for chronic limb-threatening ischemia. At the time of initial admission, two (5.4%) early deaths and three (8.1%) major amputations were noted. At 1 year after BKPB, the overall PP, SP, LS, and AFS rates were 78%, 85%, 85%, and 70%, respectively; at 3 years, they were 58%, 70%, 80%, and 52%, respectively; and at 5 years, they were 35%, 58%, 62%, and 29%, respectively. Notably, PP was significantly lower in limbs with ≤1 patent tibial arteries than in limbs with ≥2 patent artery (hazard ratio [HR], 3.80; 95% confidence interval [CI], 1.14-12.69 for overall; and HR, 12.97; 95% CI, 2.15-78.08 for distal anastomosis to below-knee popliteal artery). However, the PP was unaffected by the distal modification.
Conclusion: BKPB is a viable option for LS in patients with extensive femoropopliteal disease. Tibial runoff was significantly correlated with patency; therefore, decision-making for BKPB and follow-up must involve careful evaluation of the outflow arteries.
Keywords
Graphical Abstract
INTRODUCTION
In patients with chronic limb-threatening ischemia (CLTI), revascularization is crucial to prevent limb loss and improve quality of life. There are several techniques for revascularization, including endovascular therapy, surgical bypass, and hybrid procedures. In terms of the revascularization of patients with femoropopliteal occlusive disease, most published guidelines recommend surgical bypass with autogenous vein graft for severe lesions (e.g., TransAtlantic Inter-Society Consensus [TASC] II D lesion and heavily calcified lesions) [1,2]. However, the use of endovascular treatment for peripheral arterial occlusive disease has increased worldwide, including in Korea. Notably, endovascular treatment is preferred, accounting for 80%-95% of all procedures in peripheral arterial occlusive disease [3]. Furthermore, according to a recent guideline, an endovascular approach has been recommended in CLTI when a single-segment great saphenous vein (GSV) is absent [2].
Traditionally, below-knee (BK) bypass with a prosthetic graft had lower patency and amputation-free survival (AFS) rates than those for bypass with autogenous vein grafting [4]. Consequently, owing to these recent advances in endovascular treatment, most cases of femoropopliteal occlusive disease without an adequate autogenous vein graft have been treated via endovascular therapy. However, recent reports on the role of BK prosthetic bypass (BKPB) in the treatment of femoropopliteal occlusive disease suggest that it provides acceptable long-term patency and AFS [5,6].
Thus, the present study aimed to assess surgical complications and outcomes after BKPB, including the primary patency (PP), secondary patency (SP), limb salvage (LS) rate, and AFS rates, to guide treatment selection in patients with extensive femoropopliteal occlusive disease.
MATERIALS AND METHODS
1) Data sources and variables
This study was approved by the Institutional Review Board (IRB) of Kyungpook National University Chilgok Hospital (IRB No. 2023-03-028). The requirement for informed consent was waived due to the retrospective nature of the study. Between January 2010 and February 2022, 603 limbs in 540 patients underwent infrainguinal bypass surgery. Bypasses which underwent autogenous bypass (n=392), above-knee (AK) prosthetic graft bypass (n=133), sequential bypass (n=25), and bypass with composite graft (n=16) were excluded. This resulted in the inclusion of 37 consecutive patients who underwent BKPB for femoropopliteal occlusive disease in the current study. All included patients had an atherosclerotic arterial occlusive disease, while no non-atherosclerotic disease like Buerger disease was present. In addition, a substantial proportion of patients had a history of ipsilateral revascularization in our sample; thus, cases of acute presentation owing to thrombosis of previous revascularization was also included.
Patient characteristics, imaging findings, surgical details, and follow-up data were collected after reviewing medical records as well as pre- and postoperative imaging findings. Patient demographics included age, sex, and medical comorbidities. Prior revascularizations for ipsilateral limb and femoropopliteal occlusive disease were documented. Lesion characteristics were evaluated based on the presence of femoropopliteal occlusion, length of the occluded segment, and severity of calcification. The Peripheral Academic Research Consortium (PARC) calcium classification system was used to grade calcification as focal, mild, moderate, or severe [7], and the TASC II grading was used to rate the severity of femoropopliteal occlusive disease [8]. The runoff of tibial arteries was classified as 0, 1, 2, or 3 according to the number of patent tibial arteries running from the origin of the tibial arteries to the ankle.
Perioperative complications were classified as follows: local/nonvascular, local/vascular, or systemic/remote. These complications were graded according to the recommended standards for reports [9]. During the follow-up period, we documented and examined the following outcomes: patency of BKPB, reinterventions for the index limb, above-ankle amputations, and survival data.
2) Operative details and follow-up protocol
We performed BKPBs according to standard procedures. If the patient had combined inflow disease in the ipsilateral iliac artery, a surgical bypass, such as femoral-femoral crossover bypass, or an endovascular procedure, was performed concurrent with (or just before) the BKPB. In cases with combined common femoral arterial disease, femoral endarterectomy was performed simultaneously, with or without patch angioplasty. The main prosthetic conduit used in our series was a polytetrafluoroethylene (PTFE) graft with external reinforcement (Gore-Tex; W.L. Gore & Associates or Advanta VXT; Maquet-Atrium). A distal modification with a vein cuff or boot was created at the operator’s discretion; however, a distal modification was used in all cases of distal anastomosis to the tibial arteries. The surgeon’s preference also determined the method of distal modification, and the Miller cuff or St. Mary boot using a saphenous vein were used.
The postoperative follow-up protocol was as follows: (1) follow-up ankle-brachial index (ABI) before discharge; (2) duplex ultrasonography (DUS) and ABI at 1 month; (3) clinical follow-up at 3 months; (4) ABI follow-up at 6 months; (5) DUS and ABI at 1 year; and (6) annual DUS and ABI. During each follow-up consultation, a physical examination was performed, and sustained symptom improvement was checked; if symptoms worsened, or the ABI value decreased by over 0.15, additional DUS or computed tomography was performed. The same evaluation protocol was used for patients who developed symptoms before the scheduled follow-up, with additional procedures for further correction used if needed. Typical postoperative medications were aspirin (100 mg/day), clopidogrel (75 mg/day), and statins. The dual antiplatelet therapy was changed to a single antiplatelet agent 1 year post-operatively, unless there were indications for continued dual or anticoagulant therapy.
3) Outcomes of interest and definitions
The primary efficacy outcome was PP, while secondary outcomes included SP, LS, and AFS rates. An additional analysis of the risk factors associated with PP was performed. In addition, a subgroup analysis was performed for the LS rate in patients with CLTI, and the PP rate was calculated both for the overall sample, and in patients with distal anastomosis to the BK popliteal artery according to the runoff status. Perioperative morbidity and mortality rates assessed within 30 days after the procedure were used as the primary safety outcomes. Morbidity was classified into grades 1, 2, and 3 according to the recommended standards [9].
PP was defined as an uninterrupted patency of BKPB (i.e., patency without occlusion) occurring without the use of any surgical or endovascular reintervention. SP was defined as BKPB patency occurring after occlusion following a successful endovascular or surgical procedure. Major amputation was defined as an amputation at or above the ankle. LS rate was defined as surival time without major amputation. Finally, AFS was defined as survival time without major amputation or death from any cause (whichever occurred first). In our series, the runoff of tibial arteries was classified according to the number of patent tibial arteries from its origin to the ankle regardless of distal anastomosis site. This is because collaterals between tibial arteries exist and may be important in the patency of BKPB. Thereafter, poor tibial runoff was defined as one or less patent tibial artery.
4) Statistical analysis
The Student t-test or Mann–Whitney U-test was performed to compare continuous variables between groups depending on the normality of distribution. The chi-square test (for adequate-sized samples) or Fisher exact test (for smaller samples) was performed to compare categorical variables between groups. Kaplan–Meier plots were used to assess the PP, SP, LS, and AFS rates, whereas the log-rank test was used to determine the statistical significance of the differences between the survival curves. Cox regression analysis was performed to identify independent risk factors for PP. Due to the small number of patients and events, only two most significant factors from the univariable analysis were included in the multivariable analysis. A P-value<0.05 was considered statistically significant. We used IBM SPSS statistics (ver. 23.0; IBM Corp.) for all statistical analysis.
RESULTS
1) Patient and lesion characteristics
Overall, 37 BKPBs were performed in 37 consecutive patients during the study period. The mean age of the patients was 73 years, and 31 (83.8%) patients were male. Treatment was indicated based on the diagnosis of CLTI in 32 (86.5%) patients. Notably, there was rest pain in 16 limbs, minor tissue loss in 13 limbs (toe ulcer, n=8; toe gangrene, n=5), major tissue loss in three limbs (foot dorsum ulcer, 2; shin and heel ulcers, 1), and disabling claudication in 5 limbs. Four of the five claudicants had a history of endovascular treatment for a femoropopliteal occlusive disease that failed during follow-up, while the fifth patient presented with a severely calcified femoropopliteal lesion associated with chronic renal failure. Before surgery, these patients received conservative treatment, but their symptoms persisted. The duration of symptoms for these five patients was 3, 4, 6, 22, and 24 months, respectively. The patients consented to a prosthetic bypass after consultation.
The patient characteristics are summarized in Table 1. In total, 26 (70.3%) patients presented with a history of undergoing ≥1 ipsilateral revascularization procedure, and 24 (64.9%) patients presented with a history of undergoing femoropopliteal revascularization (endovascular treatment, surgical bypass, and surgical and endovascular treatment in 11, 11, and two patients, respectively). Of these 24 patients, 13, eight, two, and one patients underwent one, two, three, and four revascularization procedures, respectively.
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Table 1 . Patients’ characteristics.
Variable Value (n=37) Sex, male 31 (83.8) Age (y) 72.8±7.9 Indications for revascularization Claudication 5 (13.5) Chronic limb-threatening ischemia 32 (86.5) Rest pain 16 Minor tissue loss 13 Major tissue loss 3 Previous ipsilateral revascularization 26 (70.3) Previous failed FP revascularization 24 (64.9) Type of FP revascularization Endovascular therapy 11 Bypass surgery 11 Both endovascular and bypass surgery 2 Number of previous FP revascularization 1 13 2 8 3 or more 3 Hypertension 26 (70.3) Diabetes mellitus 20 (54.1) Coronary artery disease 8 (21.6) Congestive heart failure 5 (13.5) Arrhythmia 9 (24.3) Cerebrovascular disease 9 (24.3) Chronic obstructive lung disease 3 (8.1) Renal insufficiencya 11 (29.7) Dialysis 5 (13.5) Dyslipidemia 17 (45.9) Preoperative medicationb Antiplatelet agent 27 (79.4) Statin 15 (44.1) Anticoagulant 4 (11.8) Values are presented as number (%), mean±standard deviation, or number only..
FP, femoropopliteal..
aEstimated glomerular filtration rate <60 mL/min/1.73m2. bData available in 34 patients..
The lesion characteristics are summarized in Table 2. Among the femoropopliteal lesions, all patients had total occlusion, and no patient presented with only stenosis. The median femoropopliteal lesion length was 383 mm, and the median occlusion length was 330 mm. Most limb lesions (n=29; 78.4%) were classified as TASC II D. Among the limb lesion PARC calcification grades, moderate calcification was the most frequent (n=11), followed by mild calcification (n=10), severe calcification (n=9), and focal calcification (n=7). Moreover, poor distal runoff with ≤1 patent tibial artery was noted in 12 (32.4%) limbs.
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Table 2 . Lesion characteristics.
Variable Value (n=37) Chronic total occlusion 37 (100) TASC II classification C 8 (21.6) D 29 (78.4) FP lesion length (mm) 383.0 (294.5-430.0) FP occlusion length (mm) 330.0 (140.0-397.5) PARC calcium classification Focal 7 (18.9) Mild 10 (27.0) Moderate 11 (29.7) Severe 9 (24.3) Patent tibial arteries 0 1 (2.7) 1 11 (29.7) 2 18 (48.6) 3 7 (18.9) Preoperative ABI of affected limba 0.36 (0.00-0.45) Values are presented as number (%) or median (interquartile range)..
TASC, TransAtlantic Inter-Society Consensus; FP, femoropopliteal; PARC, Peripheral Academic Research Consortium; ABI, ankle-brachial index..
aData available in 32 limbs..
2) Operative characteristics
The operative characteristics are summarized in Table 3. A PTFE graft with external reinforcement was used in all patients, and the diameter was 7 mm in 34 patients and 6 mm in three patients. The inflow artery consisted of a distal external iliac artery in two patients, a common femoral artery in 34 patients, and a proximal superficial femoral artery in one patient. The outflow artery was the BK popliteal artery in 26 (70.3%) patients, followed by the posterior tibial artery in seven, the peroneal artery in two, the tibioperoneal trunk in one, and the anterior tibial artery in one patient. Distal modification was used in all cases with distal anastomosis to the tibial arteries. Half of the 26 patients with a distal anastomosis to the BK popliteal artery received a distal modification. Overall, 24 patients received a distal modification. The most common type of distal modification was St. Mary boot in 16 patients, while eight received a Miller cuff.
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Table 3 . Operative characteristics.
Variable Value (n=37) Diameter of PTFE graft 6 mm 3 (8.1) 7 mm 34 (91.9) Inflow arteries External iliac artery 2 (5.4) Common femoral artery including patch 34 (91.9) Superficial femoral artery 1 (2.7) Sites of combined inflow procedures 16 (43.2) Iliac artery 3 Common femoral artery 5 Both iliac and common femoral arteries 8 Details of combined inflow procedures Common femoral artery endarterectomy 9 Iliac artery stenting 5 Femoro-femoral bypass 5 CFA interposition graft 1 Outflow arteries Below-knee popliteal artery 26 (70.3) With distal modification 13 Without distal modification 13 Tibial arteries 11 (29.7) With distal modification 11 Combined outflow procedures 5 (13.5) Endarterectomy of below-knee popliteal artery 3 Balloon angioplasty of peroneal artery 2 Postoperative ABI of affected limba 0.95±0.15 Values are presented as number (%), number only, or mean±standard deviation..
PTFE, polytetrafluoroethylene; CFA, common femoral artery; ABI, ankle-brachial index..
aData available in 30 limbs..
Combined inflow procedures, including iliac and common femoral arterial procedures, were performed in 16 patients. The most common was femoral endarterectomy in nine patients. Outflow procedures were combined for five patients (Table 3).
3) Perioperative complications
Early perioperative complications are summarized in Supplementary Table 1. We noted two (5.4%) early mortalities and three (8.1%) major amputations during the index admission. Notably, the two patients who died had acute myocardial infarction and pneumonia, respectively. The levels of major amputation were as follows: BK in two patients (one patient underwent amputation due to sepsis despite a patent graft) and AK in one patient.
Systemic/remote, local/vascular, and local/nonvascular complications were found in 6 (16.2%), 4 (10.8%), and 11 (29.7%) patients, respectively (Supplementary Table 1). Among the systemic/remote complications, cardiac complications were the most common (occurring in four patients, including one who died, one who underwent percutaneous coronary intervention, and two who had asymptomatic elevations of troponin-I without hemodynamic disturbance). Furthermore, two patients had pneumonia and one had a cerebral infarction. One patient had both pneumonia and cerebral infarction. Among the local/vascular complications, acute graft thrombosis was seen in three patients. Further, an unexpected major amputation was necessary in one patient. Moreover, we performed major amputations in two of the three patients with acute thrombosis, whereas one patient was treated with endovascular thrombectomy. Among the local/nonvascular complications, wound hematoma and infection occurred in four patients each, and lymphocele occurred in three patients.
4) Patency, LS, and OS rates
The mean radiological follow-up duration was 27.2±31.9 months. There were 14 graft occlusions resulting in PP loss. There were no graft infections. The overall PP rates were 78%, 58%, and 35%, at 1, 3, and 5 years, respectively (Fig. 1). Of the 14 graft occlusions, 5 patients received thrombectomy (n=4) or thrombolysis (n=1). Overall, the SP rates were 85%, 70%, and 58% at 1, 3, and 5 years, respectively (Fig. 1). In the remaining nine patients with BKPB occlusion, three patients received surgical bypass with alternative vein conduits with arm vein and three patients received an inflow correction with profundaplasty, and three patients did not receive any revascularization procedures.
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Figure 1.Primary patency (PP) and secondary patency (SP) rates after below-knee prosthetic graft bypass.
The mean clinical follow-up duration was 42.8±47.0 months. Five additional major amputations occurred during follow-up. All the additional amputations were AK amputations caused by graft occlusion. Overall, the LS rate was 85%, 80%, and 62% at 1, 3, and 5 years, respectively (Fig. 2). No major amputation occurred in claudicants during follow-up. In subgroup analysis of CLTI patients (n=32), LS rates were 82%, 77%, and 57% at 1, 3, and 5 years, respectively. During the follow-up, 25 patients died from various causes. The overall survival rate was 84% at 1 year, 66% at 3 years, and 42% at 5 years (Fig. 2) and AFS rate was 70% at 1 year, 52% at 3 years, and 29% at 5 years.
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Figure 2.Limb salvage (LS) and overall survival (OS) rates after below-knee prosthetic bypass.
5) Risk factors for PP
The risk factors for PP identified after univariable and multivariable analysis are summarized in Table 4. In the univariable analysis, poor tibital runff was associated with poor PP (P=0.030). Multivariable analysis also indicated that poor tibial runoff (0/1 vs. 2/3, adjusted hazard ratio [aHR], 3.63; 95% confidence interval [CI], 1.09-12.08, P=0.036) was a statistically significant risk factor for poor PP.
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Table 4 . Risk factors for loss of primary patency: results from univariable and multivariable Cox analysis.
Variable Univariable analysis Multivariable analysis HR (95% CI) P-value aHR (95% CI) P-value Sex, male 2.23 (0.29-17.25) 0.444 Age 0.93 (0.86-1.01) 0.087 CLTI 0.53 (0.11-2.58) 0.429 Previous ipsilateral revascularization 3.44 (0.75-15.68) 0.111 Previous FP revascularization 4.09 (0.90-18.60) 0.068 3.91 (0.86-17.79) 0.078 TASC D vs. C 1.30 (0.29-5.90) 0.733 Poor runoff (0/1 vs. 2/3) 3.80 (1.14-12.69) 0.030 3.63 (1.09-12.08) 0.036 PARC severe calcification 0.87 (0.19-3.98) 0.857 Distal anastomosis (BKPA vs. tibial artery) 1.22 (0.34-4.46) 0.759 Distal modification 2.49 (0.73-8.54) 0.148 Adjunctive inflow procedures 1.39 (0.46-4.17) 0.561 Adjunctive outflow procedures 1.07 (0.14-8.35) 0.953 Hypertension 0.87 (0.28-2.72) 0.813 Diabetes mellitus 0.97 (0.32-2.97) 0.957 Coronary artery disease 2.57 (0.69-9.60) 0.161 Congestive heart failure 1.58 (0.34-7.31) 0.557 Cerebrovascular disease 0.83 (0.22-3.13) 0.788 COPD 0.65 (0.08-5.10) 0.681 Renal insufficiency 1.77 (0.54-5.85) 0.346 Dialysis 1.14 (0.14-9.10) 0.904 Dyslipidemia 1.94 (0.64-5.87) 0.243 HR, hazard ratio; CI, confidence interval; aHR, adjusted hazard ratio; CLTI, chronic limb-threatening ischemia; FP, femoropopliteal; TASC, TransAtlantic Inter-Society Consensus; PARC, Peripheral Academic Research Consortium; BKPA, below-knee popliteal artery; COPD, chronic obstructive lung disease..
Based on the comparison of the PP rates among patients in terms of the number of patent tibial arteries (0/1 vs. 2/3), the overall PP rate at 1 and 3 years was 91% and 70% in patients with ≥2 patent tibial arteries and 53% and 26% in patients with ≤1 patent tibial artery, respectively (Fig. 3A). Based on the subgroup analysis of patients with distal anastomosis to the BK popliteal artery (n=26), the overall PP rate at 1 and 3 years was 89% and 73% in patients with ≥2 patent tibial arteries, respectively, and at 1 year, it was 0% in patients with ≤1 patent tibial artery (P=0.001; Fig. 3B).
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Figure 3.Primary patency in terms of the number of patent tibial arteries (0/1 vs. 2/3). (A) Overall primary patency (n=37). (B) Primary patency in patients with distal anastomosis to the below-knee popliteal artery (n=26).
In this study, the PP was found to be similar for patients who underwent bypass with distal modification of the graft and those who did not, throughout the entire study population (HR, 2.49; 95% CI, 0.73-8.54; P=0.148). Similarly, no significant difference in PP according to distal modification was observed within the subgroup of patients whose distal anastomosis was made to the BK popliteal artery (HR, 4.32; 95% CI, 0.83-22.53; P=0.083).
DISCUSSION
The present study evaluated the outcomes of BKPB in the absence of single-segment GSV for the treatment of long-segment femoropopliteal occlusive disease. All study participants had severe femoropopliteal occlusive disease classified as TASC II C or D, and 86% of them presented with CLTI, with median lesion and occlusion lengths of 383 and 330 mm, respectively. Additionally, 70% of participants had a history of undergoing ≥1 ipsilateral revascularization, and 65% had undergone femoropopliteal revascularization. Although graft occlusion and major amputation were significant during the follow-up, SP and LS rate were 70% and 80% at 3 years, respectively; therefore, the outcomes of BKPB were deemed acceptable considering the disease severity. However, over fifty percent of patients perished within 5 years due to various causes, which is indicative of a poor prognosis in our sample.
Traditionally, compared with autogenous vein bypass, BKPB has been recognized to result in lower PP and AFS rates [4,10]. Therefore, most surgeons prefer autogenous vein grafts (including GSV and alternative vein conduits, such as the small saphenous and arm veins) for BK bypass. Additionally, owing to the advances in endovascular technology and skills, a recent guideline recommended an endovascular-first strategy for patients with long-segment femoropopliteal occlusion when GSV is unavailable or when open surgery is considered a high risk to the patient [2]. Therefore, BKPB has become the last choice for revascularization in patients with CLTI and is rarely performed in real-world clinical practice.
However, a recent report on the impact of tibial bypass conduit using Vascular Quality Initiative (VQI) data demonstrated that the PP of the prosthetic graft with a cuff at 1 year was equivalent to that of the single-segment GSV (69.1% vs. 69.1%, P=0.51). The authors suggested that prosthetic grafts were better than initially thought, especially compared to the arm vein [5]. A single-center retrospective study of endovascular treatment and BKPB with the Linton patch in TASC II D femoropopliteal lesions also confirmed the efficacy of BKPB. Notably, the PP, assisted PP, and SP rates were better in the BKPB with Linton patch group than in the endovascular treatment group [11]. Reintervention rates at 2 years were 45% and 20% in the endovascular treatment and BKPB with Linton patch groups, respectively (P=0.003).
A recent Best Endovascular Versus Best Surgical Therapy for Patients With Critical Limb Ischemia (BEST-CLI) trial that compared surgery and endovascular therapy for CLTI confirmed the importance of a good quality single-segment GSV [12]. The trial reported that 105 (55.3%) of 190 patients in the surgical group of cohort 2 (requirement of an alternative bypass conduit due to the absence of a single-segment GSV) underwent a prosthetic graft bypass. Although the overall major reintervention for the index limb was significantly higher in the endovascular therapy group in cohort 2, the primary outcome (including major adverse limb events and all-cause mortality) was similar between the two groups (42.8% vs. 47.7% in the surgical and endovascular groups, respectively; P=0.12) [12]. However, the BEST-CLI trial did not present a subgroup analysis about the results of BKPB in cohort 2 currently. In the present study, the PP rate of BKPB was 78% at 1 year and 58% at 3 years, and the LS rate was 80% at 3 years. Therefore, our findings suggest that BKPB should be considered as a viable option for these patients. In addition, it is better to await the results of the prosthetic bypass in the BEST-CLI trial, which is the intention-to-treat analysis, and identify the characteristics of femoropopliteal lesions with technical failure in endovascular treatment; then, it is anticipated that the exact role of BKPB and lesions amenable to BKPB will be confirmed in patients without single-segment GSV.
In the study based on VQI data [5], the lack of data limited the specific analysis of factors influencing the outcomes, such as vessel quality, inflow, and the size of the tibial artery outflow. In the present study, the number of patent tibial arteries was identified as an independent risk factor for the loss of PP. Furthermore, in a subgroup analysis of patients with distal anastomosis to the BK popliteal artery, the runoff was critical. The PP of BKPB in patients with ≤1 patent tibial arteries was 0% at 1 year after the operation. Moreover, the quality of runoff was identified as an independent risk factor for significant restenosis or occlusion of the target artery and reintervention in a single-center study [11]. These results suggest that tibial runoff should be considered when choosing the BKPBs. In our series, all of the included patients received BKPBs due to lack of GSV. However, the availability of alternative veins, such as arm veins and spliced veins with small saphenous veins, did not exclusively be evaluated; therefore, alternative veins may be more appropriate in patients with poor distal runoff considering disappointing patency rates after BKPB. In addition, a recent report regarding the dual pathway inhibition after recent peripheral revascularization demonstrated the consistent beneficial effect of rivaroxaban plus aspirin compared with aspirin alone, regardless of background clopidogrel, in preventing acute limb ischemia after surgery [13]. Therefore, this dual pathway inhibition may be considered as a postoperative medication.
There is ongoing debate regarding the effect of distal modification in prosthetic bypass. Initially, distal modification was introduced to enhance the patency of bypass using a prosthetic graft [14]. However, despite postulated benefits such as improved flow hemodynamics and increased capacitance to allow for intimal hyperplasia [15,16], the results evaluating the performance of distal modification have been inconclusive and inconsistent. Several reports with a venous adjunct at the distal anastomosis have been associated with improved PP and decreased major adverse limb events after BKPB [17,18]. Conversely, some reports have demonstrated no improvement in patency and clinical outcomes, such as limb loss [19,20]. This controversy has been reflected in randomized controlled trials. The Joint Vascular Research Group demonstrated superior 3-year patency rates of femoral to BK popliteal artery in the group with a Miller cuff inserted, compared with the non-cuffed group (45% vs. 19%, P=0.018) [18]. However, the Scandinavian Miller Collar Study showed no benefit with a reported 3-year PP of 26% in the vein collar group and 43% in the no-vein collar group [20]. In addition, the SP and LS rates were similar in both groups. In our study, the distal modification did not improve patients’ overall PP (P=0.148). Neither did distal anastomosis to the BK popliteal artery (P=0.083). However, there could have been a selection bias in our series’ decision to use distal modification. For example, suppose the recipient artery was calcified or small in diameter, particularly in the BK popliteal artery. In that case, the distal modification may have been constructed by operators with the expectation of improvement in patency and surgical outcomes.
This retrospective study has several limitations. First, the study results were based on a single-center experience with a relatively short follow-up time and fewer patients. Second, we did not include a control group; for example, the group of patients undergoing endovascular therapy or autogenous bypass with single-segment GSV. To determine the precise role of BKPB and its potential use as a primary revascularization method in certain long-segment femoropopliteal occlusive diseases, endovascular treatments with the most advanced devices and techniques must be evaluated, and their outcomes must be compared. However, consistent with the global trends, our hospital policy states that bypass with single-segment GSV or endovascular treatment was the preferred option for such patients. Indeed, 70% of the participants had a history of previous endovascular treatment or surgical bypass in the present study. Third, we could not analyze some essential variables, such as postoperative medication, which could have affected our outcome. Although most patients were prescribed dual antiplatelet agents and statin at the time of discharge, many patients were subsequently taking their medications at another hospital, and some patients presented with recurrent symptoms after follow-up loss; therefore, it was difficult to ascertain whether the patients took their postoperative medication correctly. Finally, although consecutive patients were included in the study, a selection bias might be inevitable in terms of the suitability for anesthesia and the presence of a recipient artery. In other words, BKPB was not performed if the patients were deemed unsuitable for anesthesia or had poor or no recipient arteries. Therefore, our sample did not represent the overall cohort of patients with CLTI; hence, the study results should be interpreted cautiously.
CONCLUSION
Although early complications, graft occlusion, and major amputation were found to be significant during the follow-up, BKPB remains a viable option for LS in extensive femoropopliteal occlusive disease. We found that tibial runoff is associated with patency; therefore, we propose that decision-making for BKPB should be performed based on the careful evaluation of the outflow arteries, and thorough follow-up is necessary regarding the development of adverse events in the poor tibial runoff.
SUPPLEMENTARY MATERIAL
Supplementary Table can be found via https://doi.org/10.5758/vsi.230028
FUNDING
None.
CONFLICTS OF INTEREST
Hyung-Kee Kim has been the editor-in-chief of the VSI since 2023. Woo-Sung Yun has been the senior editor of the VSI since 2023. They were not involved in the review process. Otherwise, no potential conflict of interest relevant to this article was reported.
AUTHOR CONTRIBUTIONS
Conception and design: SH, HKK. Analysis and interpretation: WSY, DH, HKK. Data collection: YK, JHJ, DH. Writing the article: YK, JHJ, HKK. Critical revision of the article: WSY, SH, HKK. Final approval of the article: all authors. Statistical analysis: DH, HKK. Obtained funding: none. Overall responsibility: HKK.
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Related articles in VSI
Article
Original Article
Vasc Specialist Int (2023) 39:16
Published online June 29, 2023 https://doi.org/10.5758/vsi.230028
Copyright © The Korean Society for Vascular Surgery.
Below-Knee Prosthetic Bypass Is a Viable Option for Limb Salvage in Patients with Extensive Femoropopliteal Occlusive Disease
Younghye Kim1 , Ji Hyun Jung2 , Deokbi Hwang1 , Woo-Sung Yun1 , Seung Huh1 , and Hyung-Kee Kim2
1Division of Vascular and Endovascular Surgery, Department of Surgery, Kyungpook National University Hospital, Daegu, 2Division of Vascular and Endovascular Surgery, Department of Surgery, Kyungpook National University Chilgok Hospital, Kyungpook National University School of Medicine, Daegu, Korea
Correspondence to:Hyung-Kee Kim
Division of Vascular and Endovascular Surgery, Department of Surgery, Kyungpook National University Chilgok Hospital, 807 Hoguk-ro, Buk-gu, Daegu, 41404, Korea
Tel: 82-53-200-5605
Fax: 82-53-421-0510
E-mail: hkkim6260@knu.ac.kr
https://orcid.org/0000-0002-4436-7424
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Purpose: This study aimed to (1) evaluate the outcomes of below-knee prosthetic bypass (BKPB) in the absence of the great saphenous vein, and (2) identify risk factors associated with these outcomes.
Materials and Methods: This study included 37 consecutive patients who underwent BKPB with or without distal modification between 2010 and 2022. We further assessed the following treatment outcomes: primary patency (PP), secondary patency (SP), limb salvage (LS), and amputation-free survival (AFS) rates. The risk factors for PP were also examined.
Results: Most patients (n=31) were male. In 32 (86.5%) patients, BKPBs were performed for chronic limb-threatening ischemia. At the time of initial admission, two (5.4%) early deaths and three (8.1%) major amputations were noted. At 1 year after BKPB, the overall PP, SP, LS, and AFS rates were 78%, 85%, 85%, and 70%, respectively; at 3 years, they were 58%, 70%, 80%, and 52%, respectively; and at 5 years, they were 35%, 58%, 62%, and 29%, respectively. Notably, PP was significantly lower in limbs with ≤1 patent tibial arteries than in limbs with ≥2 patent artery (hazard ratio [HR], 3.80; 95% confidence interval [CI], 1.14-12.69 for overall; and HR, 12.97; 95% CI, 2.15-78.08 for distal anastomosis to below-knee popliteal artery). However, the PP was unaffected by the distal modification.
Conclusion: BKPB is a viable option for LS in patients with extensive femoropopliteal disease. Tibial runoff was significantly correlated with patency; therefore, decision-making for BKPB and follow-up must involve careful evaluation of the outflow arteries.
Keywords: Peripheral arterial disease, Vascular surgical procedures, Prostheses and implants, Polytetrafluoroethylene, Treatment outcome
INTRODUCTION
In patients with chronic limb-threatening ischemia (CLTI), revascularization is crucial to prevent limb loss and improve quality of life. There are several techniques for revascularization, including endovascular therapy, surgical bypass, and hybrid procedures. In terms of the revascularization of patients with femoropopliteal occlusive disease, most published guidelines recommend surgical bypass with autogenous vein graft for severe lesions (e.g., TransAtlantic Inter-Society Consensus [TASC] II D lesion and heavily calcified lesions) [1,2]. However, the use of endovascular treatment for peripheral arterial occlusive disease has increased worldwide, including in Korea. Notably, endovascular treatment is preferred, accounting for 80%-95% of all procedures in peripheral arterial occlusive disease [3]. Furthermore, according to a recent guideline, an endovascular approach has been recommended in CLTI when a single-segment great saphenous vein (GSV) is absent [2].
Traditionally, below-knee (BK) bypass with a prosthetic graft had lower patency and amputation-free survival (AFS) rates than those for bypass with autogenous vein grafting [4]. Consequently, owing to these recent advances in endovascular treatment, most cases of femoropopliteal occlusive disease without an adequate autogenous vein graft have been treated via endovascular therapy. However, recent reports on the role of BK prosthetic bypass (BKPB) in the treatment of femoropopliteal occlusive disease suggest that it provides acceptable long-term patency and AFS [5,6].
Thus, the present study aimed to assess surgical complications and outcomes after BKPB, including the primary patency (PP), secondary patency (SP), limb salvage (LS) rate, and AFS rates, to guide treatment selection in patients with extensive femoropopliteal occlusive disease.
MATERIALS AND METHODS
1) Data sources and variables
This study was approved by the Institutional Review Board (IRB) of Kyungpook National University Chilgok Hospital (IRB No. 2023-03-028). The requirement for informed consent was waived due to the retrospective nature of the study. Between January 2010 and February 2022, 603 limbs in 540 patients underwent infrainguinal bypass surgery. Bypasses which underwent autogenous bypass (n=392), above-knee (AK) prosthetic graft bypass (n=133), sequential bypass (n=25), and bypass with composite graft (n=16) were excluded. This resulted in the inclusion of 37 consecutive patients who underwent BKPB for femoropopliteal occlusive disease in the current study. All included patients had an atherosclerotic arterial occlusive disease, while no non-atherosclerotic disease like Buerger disease was present. In addition, a substantial proportion of patients had a history of ipsilateral revascularization in our sample; thus, cases of acute presentation owing to thrombosis of previous revascularization was also included.
Patient characteristics, imaging findings, surgical details, and follow-up data were collected after reviewing medical records as well as pre- and postoperative imaging findings. Patient demographics included age, sex, and medical comorbidities. Prior revascularizations for ipsilateral limb and femoropopliteal occlusive disease were documented. Lesion characteristics were evaluated based on the presence of femoropopliteal occlusion, length of the occluded segment, and severity of calcification. The Peripheral Academic Research Consortium (PARC) calcium classification system was used to grade calcification as focal, mild, moderate, or severe [7], and the TASC II grading was used to rate the severity of femoropopliteal occlusive disease [8]. The runoff of tibial arteries was classified as 0, 1, 2, or 3 according to the number of patent tibial arteries running from the origin of the tibial arteries to the ankle.
Perioperative complications were classified as follows: local/nonvascular, local/vascular, or systemic/remote. These complications were graded according to the recommended standards for reports [9]. During the follow-up period, we documented and examined the following outcomes: patency of BKPB, reinterventions for the index limb, above-ankle amputations, and survival data.
2) Operative details and follow-up protocol
We performed BKPBs according to standard procedures. If the patient had combined inflow disease in the ipsilateral iliac artery, a surgical bypass, such as femoral-femoral crossover bypass, or an endovascular procedure, was performed concurrent with (or just before) the BKPB. In cases with combined common femoral arterial disease, femoral endarterectomy was performed simultaneously, with or without patch angioplasty. The main prosthetic conduit used in our series was a polytetrafluoroethylene (PTFE) graft with external reinforcement (Gore-Tex; W.L. Gore & Associates or Advanta VXT; Maquet-Atrium). A distal modification with a vein cuff or boot was created at the operator’s discretion; however, a distal modification was used in all cases of distal anastomosis to the tibial arteries. The surgeon’s preference also determined the method of distal modification, and the Miller cuff or St. Mary boot using a saphenous vein were used.
The postoperative follow-up protocol was as follows: (1) follow-up ankle-brachial index (ABI) before discharge; (2) duplex ultrasonography (DUS) and ABI at 1 month; (3) clinical follow-up at 3 months; (4) ABI follow-up at 6 months; (5) DUS and ABI at 1 year; and (6) annual DUS and ABI. During each follow-up consultation, a physical examination was performed, and sustained symptom improvement was checked; if symptoms worsened, or the ABI value decreased by over 0.15, additional DUS or computed tomography was performed. The same evaluation protocol was used for patients who developed symptoms before the scheduled follow-up, with additional procedures for further correction used if needed. Typical postoperative medications were aspirin (100 mg/day), clopidogrel (75 mg/day), and statins. The dual antiplatelet therapy was changed to a single antiplatelet agent 1 year post-operatively, unless there were indications for continued dual or anticoagulant therapy.
3) Outcomes of interest and definitions
The primary efficacy outcome was PP, while secondary outcomes included SP, LS, and AFS rates. An additional analysis of the risk factors associated with PP was performed. In addition, a subgroup analysis was performed for the LS rate in patients with CLTI, and the PP rate was calculated both for the overall sample, and in patients with distal anastomosis to the BK popliteal artery according to the runoff status. Perioperative morbidity and mortality rates assessed within 30 days after the procedure were used as the primary safety outcomes. Morbidity was classified into grades 1, 2, and 3 according to the recommended standards [9].
PP was defined as an uninterrupted patency of BKPB (i.e., patency without occlusion) occurring without the use of any surgical or endovascular reintervention. SP was defined as BKPB patency occurring after occlusion following a successful endovascular or surgical procedure. Major amputation was defined as an amputation at or above the ankle. LS rate was defined as surival time without major amputation. Finally, AFS was defined as survival time without major amputation or death from any cause (whichever occurred first). In our series, the runoff of tibial arteries was classified according to the number of patent tibial arteries from its origin to the ankle regardless of distal anastomosis site. This is because collaterals between tibial arteries exist and may be important in the patency of BKPB. Thereafter, poor tibial runoff was defined as one or less patent tibial artery.
4) Statistical analysis
The Student t-test or Mann–Whitney U-test was performed to compare continuous variables between groups depending on the normality of distribution. The chi-square test (for adequate-sized samples) or Fisher exact test (for smaller samples) was performed to compare categorical variables between groups. Kaplan–Meier plots were used to assess the PP, SP, LS, and AFS rates, whereas the log-rank test was used to determine the statistical significance of the differences between the survival curves. Cox regression analysis was performed to identify independent risk factors for PP. Due to the small number of patients and events, only two most significant factors from the univariable analysis were included in the multivariable analysis. A P-value<0.05 was considered statistically significant. We used IBM SPSS statistics (ver. 23.0; IBM Corp.) for all statistical analysis.
RESULTS
1) Patient and lesion characteristics
Overall, 37 BKPBs were performed in 37 consecutive patients during the study period. The mean age of the patients was 73 years, and 31 (83.8%) patients were male. Treatment was indicated based on the diagnosis of CLTI in 32 (86.5%) patients. Notably, there was rest pain in 16 limbs, minor tissue loss in 13 limbs (toe ulcer, n=8; toe gangrene, n=5), major tissue loss in three limbs (foot dorsum ulcer, 2; shin and heel ulcers, 1), and disabling claudication in 5 limbs. Four of the five claudicants had a history of endovascular treatment for a femoropopliteal occlusive disease that failed during follow-up, while the fifth patient presented with a severely calcified femoropopliteal lesion associated with chronic renal failure. Before surgery, these patients received conservative treatment, but their symptoms persisted. The duration of symptoms for these five patients was 3, 4, 6, 22, and 24 months, respectively. The patients consented to a prosthetic bypass after consultation.
The patient characteristics are summarized in Table 1. In total, 26 (70.3%) patients presented with a history of undergoing ≥1 ipsilateral revascularization procedure, and 24 (64.9%) patients presented with a history of undergoing femoropopliteal revascularization (endovascular treatment, surgical bypass, and surgical and endovascular treatment in 11, 11, and two patients, respectively). Of these 24 patients, 13, eight, two, and one patients underwent one, two, three, and four revascularization procedures, respectively.
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Table 1 . Patients’ characteristics.
Variable Value (n=37) Sex, male 31 (83.8) Age (y) 72.8±7.9 Indications for revascularization Claudication 5 (13.5) Chronic limb-threatening ischemia 32 (86.5) Rest pain 16 Minor tissue loss 13 Major tissue loss 3 Previous ipsilateral revascularization 26 (70.3) Previous failed FP revascularization 24 (64.9) Type of FP revascularization Endovascular therapy 11 Bypass surgery 11 Both endovascular and bypass surgery 2 Number of previous FP revascularization 1 13 2 8 3 or more 3 Hypertension 26 (70.3) Diabetes mellitus 20 (54.1) Coronary artery disease 8 (21.6) Congestive heart failure 5 (13.5) Arrhythmia 9 (24.3) Cerebrovascular disease 9 (24.3) Chronic obstructive lung disease 3 (8.1) Renal insufficiencya 11 (29.7) Dialysis 5 (13.5) Dyslipidemia 17 (45.9) Preoperative medicationb Antiplatelet agent 27 (79.4) Statin 15 (44.1) Anticoagulant 4 (11.8) Values are presented as number (%), mean±standard deviation, or number only..
FP, femoropopliteal..
aEstimated glomerular filtration rate <60 mL/min/1.73m2. bData available in 34 patients..
The lesion characteristics are summarized in Table 2. Among the femoropopliteal lesions, all patients had total occlusion, and no patient presented with only stenosis. The median femoropopliteal lesion length was 383 mm, and the median occlusion length was 330 mm. Most limb lesions (n=29; 78.4%) were classified as TASC II D. Among the limb lesion PARC calcification grades, moderate calcification was the most frequent (n=11), followed by mild calcification (n=10), severe calcification (n=9), and focal calcification (n=7). Moreover, poor distal runoff with ≤1 patent tibial artery was noted in 12 (32.4%) limbs.
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Table 2 . Lesion characteristics.
Variable Value (n=37) Chronic total occlusion 37 (100) TASC II classification C 8 (21.6) D 29 (78.4) FP lesion length (mm) 383.0 (294.5-430.0) FP occlusion length (mm) 330.0 (140.0-397.5) PARC calcium classification Focal 7 (18.9) Mild 10 (27.0) Moderate 11 (29.7) Severe 9 (24.3) Patent tibial arteries 0 1 (2.7) 1 11 (29.7) 2 18 (48.6) 3 7 (18.9) Preoperative ABI of affected limba 0.36 (0.00-0.45) Values are presented as number (%) or median (interquartile range)..
TASC, TransAtlantic Inter-Society Consensus; FP, femoropopliteal; PARC, Peripheral Academic Research Consortium; ABI, ankle-brachial index..
aData available in 32 limbs..
2) Operative characteristics
The operative characteristics are summarized in Table 3. A PTFE graft with external reinforcement was used in all patients, and the diameter was 7 mm in 34 patients and 6 mm in three patients. The inflow artery consisted of a distal external iliac artery in two patients, a common femoral artery in 34 patients, and a proximal superficial femoral artery in one patient. The outflow artery was the BK popliteal artery in 26 (70.3%) patients, followed by the posterior tibial artery in seven, the peroneal artery in two, the tibioperoneal trunk in one, and the anterior tibial artery in one patient. Distal modification was used in all cases with distal anastomosis to the tibial arteries. Half of the 26 patients with a distal anastomosis to the BK popliteal artery received a distal modification. Overall, 24 patients received a distal modification. The most common type of distal modification was St. Mary boot in 16 patients, while eight received a Miller cuff.
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Table 3 . Operative characteristics.
Variable Value (n=37) Diameter of PTFE graft 6 mm 3 (8.1) 7 mm 34 (91.9) Inflow arteries External iliac artery 2 (5.4) Common femoral artery including patch 34 (91.9) Superficial femoral artery 1 (2.7) Sites of combined inflow procedures 16 (43.2) Iliac artery 3 Common femoral artery 5 Both iliac and common femoral arteries 8 Details of combined inflow procedures Common femoral artery endarterectomy 9 Iliac artery stenting 5 Femoro-femoral bypass 5 CFA interposition graft 1 Outflow arteries Below-knee popliteal artery 26 (70.3) With distal modification 13 Without distal modification 13 Tibial arteries 11 (29.7) With distal modification 11 Combined outflow procedures 5 (13.5) Endarterectomy of below-knee popliteal artery 3 Balloon angioplasty of peroneal artery 2 Postoperative ABI of affected limba 0.95±0.15 Values are presented as number (%), number only, or mean±standard deviation..
PTFE, polytetrafluoroethylene; CFA, common femoral artery; ABI, ankle-brachial index..
aData available in 30 limbs..
Combined inflow procedures, including iliac and common femoral arterial procedures, were performed in 16 patients. The most common was femoral endarterectomy in nine patients. Outflow procedures were combined for five patients (Table 3).
3) Perioperative complications
Early perioperative complications are summarized in Supplementary Table 1. We noted two (5.4%) early mortalities and three (8.1%) major amputations during the index admission. Notably, the two patients who died had acute myocardial infarction and pneumonia, respectively. The levels of major amputation were as follows: BK in two patients (one patient underwent amputation due to sepsis despite a patent graft) and AK in one patient.
Systemic/remote, local/vascular, and local/nonvascular complications were found in 6 (16.2%), 4 (10.8%), and 11 (29.7%) patients, respectively (Supplementary Table 1). Among the systemic/remote complications, cardiac complications were the most common (occurring in four patients, including one who died, one who underwent percutaneous coronary intervention, and two who had asymptomatic elevations of troponin-I without hemodynamic disturbance). Furthermore, two patients had pneumonia and one had a cerebral infarction. One patient had both pneumonia and cerebral infarction. Among the local/vascular complications, acute graft thrombosis was seen in three patients. Further, an unexpected major amputation was necessary in one patient. Moreover, we performed major amputations in two of the three patients with acute thrombosis, whereas one patient was treated with endovascular thrombectomy. Among the local/nonvascular complications, wound hematoma and infection occurred in four patients each, and lymphocele occurred in three patients.
4) Patency, LS, and OS rates
The mean radiological follow-up duration was 27.2±31.9 months. There were 14 graft occlusions resulting in PP loss. There were no graft infections. The overall PP rates were 78%, 58%, and 35%, at 1, 3, and 5 years, respectively (Fig. 1). Of the 14 graft occlusions, 5 patients received thrombectomy (n=4) or thrombolysis (n=1). Overall, the SP rates were 85%, 70%, and 58% at 1, 3, and 5 years, respectively (Fig. 1). In the remaining nine patients with BKPB occlusion, three patients received surgical bypass with alternative vein conduits with arm vein and three patients received an inflow correction with profundaplasty, and three patients did not receive any revascularization procedures.
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Figure 1. Primary patency (PP) and secondary patency (SP) rates after below-knee prosthetic graft bypass.
The mean clinical follow-up duration was 42.8±47.0 months. Five additional major amputations occurred during follow-up. All the additional amputations were AK amputations caused by graft occlusion. Overall, the LS rate was 85%, 80%, and 62% at 1, 3, and 5 years, respectively (Fig. 2). No major amputation occurred in claudicants during follow-up. In subgroup analysis of CLTI patients (n=32), LS rates were 82%, 77%, and 57% at 1, 3, and 5 years, respectively. During the follow-up, 25 patients died from various causes. The overall survival rate was 84% at 1 year, 66% at 3 years, and 42% at 5 years (Fig. 2) and AFS rate was 70% at 1 year, 52% at 3 years, and 29% at 5 years.
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Figure 2. Limb salvage (LS) and overall survival (OS) rates after below-knee prosthetic bypass.
5) Risk factors for PP
The risk factors for PP identified after univariable and multivariable analysis are summarized in Table 4. In the univariable analysis, poor tibital runff was associated with poor PP (P=0.030). Multivariable analysis also indicated that poor tibial runoff (0/1 vs. 2/3, adjusted hazard ratio [aHR], 3.63; 95% confidence interval [CI], 1.09-12.08, P=0.036) was a statistically significant risk factor for poor PP.
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Table 4 . Risk factors for loss of primary patency: results from univariable and multivariable Cox analysis.
Variable Univariable analysis Multivariable analysis HR (95% CI) P-value aHR (95% CI) P-value Sex, male 2.23 (0.29-17.25) 0.444 Age 0.93 (0.86-1.01) 0.087 CLTI 0.53 (0.11-2.58) 0.429 Previous ipsilateral revascularization 3.44 (0.75-15.68) 0.111 Previous FP revascularization 4.09 (0.90-18.60) 0.068 3.91 (0.86-17.79) 0.078 TASC D vs. C 1.30 (0.29-5.90) 0.733 Poor runoff (0/1 vs. 2/3) 3.80 (1.14-12.69) 0.030 3.63 (1.09-12.08) 0.036 PARC severe calcification 0.87 (0.19-3.98) 0.857 Distal anastomosis (BKPA vs. tibial artery) 1.22 (0.34-4.46) 0.759 Distal modification 2.49 (0.73-8.54) 0.148 Adjunctive inflow procedures 1.39 (0.46-4.17) 0.561 Adjunctive outflow procedures 1.07 (0.14-8.35) 0.953 Hypertension 0.87 (0.28-2.72) 0.813 Diabetes mellitus 0.97 (0.32-2.97) 0.957 Coronary artery disease 2.57 (0.69-9.60) 0.161 Congestive heart failure 1.58 (0.34-7.31) 0.557 Cerebrovascular disease 0.83 (0.22-3.13) 0.788 COPD 0.65 (0.08-5.10) 0.681 Renal insufficiency 1.77 (0.54-5.85) 0.346 Dialysis 1.14 (0.14-9.10) 0.904 Dyslipidemia 1.94 (0.64-5.87) 0.243 HR, hazard ratio; CI, confidence interval; aHR, adjusted hazard ratio; CLTI, chronic limb-threatening ischemia; FP, femoropopliteal; TASC, TransAtlantic Inter-Society Consensus; PARC, Peripheral Academic Research Consortium; BKPA, below-knee popliteal artery; COPD, chronic obstructive lung disease..
Based on the comparison of the PP rates among patients in terms of the number of patent tibial arteries (0/1 vs. 2/3), the overall PP rate at 1 and 3 years was 91% and 70% in patients with ≥2 patent tibial arteries and 53% and 26% in patients with ≤1 patent tibial artery, respectively (Fig. 3A). Based on the subgroup analysis of patients with distal anastomosis to the BK popliteal artery (n=26), the overall PP rate at 1 and 3 years was 89% and 73% in patients with ≥2 patent tibial arteries, respectively, and at 1 year, it was 0% in patients with ≤1 patent tibial artery (P=0.001; Fig. 3B).
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Figure 3. Primary patency in terms of the number of patent tibial arteries (0/1 vs. 2/3). (A) Overall primary patency (n=37). (B) Primary patency in patients with distal anastomosis to the below-knee popliteal artery (n=26).
In this study, the PP was found to be similar for patients who underwent bypass with distal modification of the graft and those who did not, throughout the entire study population (HR, 2.49; 95% CI, 0.73-8.54; P=0.148). Similarly, no significant difference in PP according to distal modification was observed within the subgroup of patients whose distal anastomosis was made to the BK popliteal artery (HR, 4.32; 95% CI, 0.83-22.53; P=0.083).
DISCUSSION
The present study evaluated the outcomes of BKPB in the absence of single-segment GSV for the treatment of long-segment femoropopliteal occlusive disease. All study participants had severe femoropopliteal occlusive disease classified as TASC II C or D, and 86% of them presented with CLTI, with median lesion and occlusion lengths of 383 and 330 mm, respectively. Additionally, 70% of participants had a history of undergoing ≥1 ipsilateral revascularization, and 65% had undergone femoropopliteal revascularization. Although graft occlusion and major amputation were significant during the follow-up, SP and LS rate were 70% and 80% at 3 years, respectively; therefore, the outcomes of BKPB were deemed acceptable considering the disease severity. However, over fifty percent of patients perished within 5 years due to various causes, which is indicative of a poor prognosis in our sample.
Traditionally, compared with autogenous vein bypass, BKPB has been recognized to result in lower PP and AFS rates [4,10]. Therefore, most surgeons prefer autogenous vein grafts (including GSV and alternative vein conduits, such as the small saphenous and arm veins) for BK bypass. Additionally, owing to the advances in endovascular technology and skills, a recent guideline recommended an endovascular-first strategy for patients with long-segment femoropopliteal occlusion when GSV is unavailable or when open surgery is considered a high risk to the patient [2]. Therefore, BKPB has become the last choice for revascularization in patients with CLTI and is rarely performed in real-world clinical practice.
However, a recent report on the impact of tibial bypass conduit using Vascular Quality Initiative (VQI) data demonstrated that the PP of the prosthetic graft with a cuff at 1 year was equivalent to that of the single-segment GSV (69.1% vs. 69.1%, P=0.51). The authors suggested that prosthetic grafts were better than initially thought, especially compared to the arm vein [5]. A single-center retrospective study of endovascular treatment and BKPB with the Linton patch in TASC II D femoropopliteal lesions also confirmed the efficacy of BKPB. Notably, the PP, assisted PP, and SP rates were better in the BKPB with Linton patch group than in the endovascular treatment group [11]. Reintervention rates at 2 years were 45% and 20% in the endovascular treatment and BKPB with Linton patch groups, respectively (P=0.003).
A recent Best Endovascular Versus Best Surgical Therapy for Patients With Critical Limb Ischemia (BEST-CLI) trial that compared surgery and endovascular therapy for CLTI confirmed the importance of a good quality single-segment GSV [12]. The trial reported that 105 (55.3%) of 190 patients in the surgical group of cohort 2 (requirement of an alternative bypass conduit due to the absence of a single-segment GSV) underwent a prosthetic graft bypass. Although the overall major reintervention for the index limb was significantly higher in the endovascular therapy group in cohort 2, the primary outcome (including major adverse limb events and all-cause mortality) was similar between the two groups (42.8% vs. 47.7% in the surgical and endovascular groups, respectively; P=0.12) [12]. However, the BEST-CLI trial did not present a subgroup analysis about the results of BKPB in cohort 2 currently. In the present study, the PP rate of BKPB was 78% at 1 year and 58% at 3 years, and the LS rate was 80% at 3 years. Therefore, our findings suggest that BKPB should be considered as a viable option for these patients. In addition, it is better to await the results of the prosthetic bypass in the BEST-CLI trial, which is the intention-to-treat analysis, and identify the characteristics of femoropopliteal lesions with technical failure in endovascular treatment; then, it is anticipated that the exact role of BKPB and lesions amenable to BKPB will be confirmed in patients without single-segment GSV.
In the study based on VQI data [5], the lack of data limited the specific analysis of factors influencing the outcomes, such as vessel quality, inflow, and the size of the tibial artery outflow. In the present study, the number of patent tibial arteries was identified as an independent risk factor for the loss of PP. Furthermore, in a subgroup analysis of patients with distal anastomosis to the BK popliteal artery, the runoff was critical. The PP of BKPB in patients with ≤1 patent tibial arteries was 0% at 1 year after the operation. Moreover, the quality of runoff was identified as an independent risk factor for significant restenosis or occlusion of the target artery and reintervention in a single-center study [11]. These results suggest that tibial runoff should be considered when choosing the BKPBs. In our series, all of the included patients received BKPBs due to lack of GSV. However, the availability of alternative veins, such as arm veins and spliced veins with small saphenous veins, did not exclusively be evaluated; therefore, alternative veins may be more appropriate in patients with poor distal runoff considering disappointing patency rates after BKPB. In addition, a recent report regarding the dual pathway inhibition after recent peripheral revascularization demonstrated the consistent beneficial effect of rivaroxaban plus aspirin compared with aspirin alone, regardless of background clopidogrel, in preventing acute limb ischemia after surgery [13]. Therefore, this dual pathway inhibition may be considered as a postoperative medication.
There is ongoing debate regarding the effect of distal modification in prosthetic bypass. Initially, distal modification was introduced to enhance the patency of bypass using a prosthetic graft [14]. However, despite postulated benefits such as improved flow hemodynamics and increased capacitance to allow for intimal hyperplasia [15,16], the results evaluating the performance of distal modification have been inconclusive and inconsistent. Several reports with a venous adjunct at the distal anastomosis have been associated with improved PP and decreased major adverse limb events after BKPB [17,18]. Conversely, some reports have demonstrated no improvement in patency and clinical outcomes, such as limb loss [19,20]. This controversy has been reflected in randomized controlled trials. The Joint Vascular Research Group demonstrated superior 3-year patency rates of femoral to BK popliteal artery in the group with a Miller cuff inserted, compared with the non-cuffed group (45% vs. 19%, P=0.018) [18]. However, the Scandinavian Miller Collar Study showed no benefit with a reported 3-year PP of 26% in the vein collar group and 43% in the no-vein collar group [20]. In addition, the SP and LS rates were similar in both groups. In our study, the distal modification did not improve patients’ overall PP (P=0.148). Neither did distal anastomosis to the BK popliteal artery (P=0.083). However, there could have been a selection bias in our series’ decision to use distal modification. For example, suppose the recipient artery was calcified or small in diameter, particularly in the BK popliteal artery. In that case, the distal modification may have been constructed by operators with the expectation of improvement in patency and surgical outcomes.
This retrospective study has several limitations. First, the study results were based on a single-center experience with a relatively short follow-up time and fewer patients. Second, we did not include a control group; for example, the group of patients undergoing endovascular therapy or autogenous bypass with single-segment GSV. To determine the precise role of BKPB and its potential use as a primary revascularization method in certain long-segment femoropopliteal occlusive diseases, endovascular treatments with the most advanced devices and techniques must be evaluated, and their outcomes must be compared. However, consistent with the global trends, our hospital policy states that bypass with single-segment GSV or endovascular treatment was the preferred option for such patients. Indeed, 70% of the participants had a history of previous endovascular treatment or surgical bypass in the present study. Third, we could not analyze some essential variables, such as postoperative medication, which could have affected our outcome. Although most patients were prescribed dual antiplatelet agents and statin at the time of discharge, many patients were subsequently taking their medications at another hospital, and some patients presented with recurrent symptoms after follow-up loss; therefore, it was difficult to ascertain whether the patients took their postoperative medication correctly. Finally, although consecutive patients were included in the study, a selection bias might be inevitable in terms of the suitability for anesthesia and the presence of a recipient artery. In other words, BKPB was not performed if the patients were deemed unsuitable for anesthesia or had poor or no recipient arteries. Therefore, our sample did not represent the overall cohort of patients with CLTI; hence, the study results should be interpreted cautiously.
CONCLUSION
Although early complications, graft occlusion, and major amputation were found to be significant during the follow-up, BKPB remains a viable option for LS in extensive femoropopliteal occlusive disease. We found that tibial runoff is associated with patency; therefore, we propose that decision-making for BKPB should be performed based on the careful evaluation of the outflow arteries, and thorough follow-up is necessary regarding the development of adverse events in the poor tibial runoff.
SUPPLEMENTARY MATERIAL
Supplementary Table can be found via https://doi.org/10.5758/vsi.230028
FUNDING
None.
CONFLICTS OF INTEREST
Hyung-Kee Kim has been the editor-in-chief of the VSI since 2023. Woo-Sung Yun has been the senior editor of the VSI since 2023. They were not involved in the review process. Otherwise, no potential conflict of interest relevant to this article was reported.
AUTHOR CONTRIBUTIONS
Conception and design: SH, HKK. Analysis and interpretation: WSY, DH, HKK. Data collection: YK, JHJ, DH. Writing the article: YK, JHJ, HKK. Critical revision of the article: WSY, SH, HKK. Final approval of the article: all authors. Statistical analysis: DH, HKK. Obtained funding: none. Overall responsibility: HKK.
Fig 1.
Fig 2.
Fig 3.
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Table 1 . Patients’ characteristics.
Variable Value (n=37) Sex, male 31 (83.8) Age (y) 72.8±7.9 Indications for revascularization Claudication 5 (13.5) Chronic limb-threatening ischemia 32 (86.5) Rest pain 16 Minor tissue loss 13 Major tissue loss 3 Previous ipsilateral revascularization 26 (70.3) Previous failed FP revascularization 24 (64.9) Type of FP revascularization Endovascular therapy 11 Bypass surgery 11 Both endovascular and bypass surgery 2 Number of previous FP revascularization 1 13 2 8 3 or more 3 Hypertension 26 (70.3) Diabetes mellitus 20 (54.1) Coronary artery disease 8 (21.6) Congestive heart failure 5 (13.5) Arrhythmia 9 (24.3) Cerebrovascular disease 9 (24.3) Chronic obstructive lung disease 3 (8.1) Renal insufficiencya 11 (29.7) Dialysis 5 (13.5) Dyslipidemia 17 (45.9) Preoperative medicationb Antiplatelet agent 27 (79.4) Statin 15 (44.1) Anticoagulant 4 (11.8) Values are presented as number (%), mean±standard deviation, or number only..
FP, femoropopliteal..
aEstimated glomerular filtration rate <60 mL/min/1.73m2. bData available in 34 patients..
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Table 2 . Lesion characteristics.
Variable Value (n=37) Chronic total occlusion 37 (100) TASC II classification C 8 (21.6) D 29 (78.4) FP lesion length (mm) 383.0 (294.5-430.0) FP occlusion length (mm) 330.0 (140.0-397.5) PARC calcium classification Focal 7 (18.9) Mild 10 (27.0) Moderate 11 (29.7) Severe 9 (24.3) Patent tibial arteries 0 1 (2.7) 1 11 (29.7) 2 18 (48.6) 3 7 (18.9) Preoperative ABI of affected limba 0.36 (0.00-0.45) Values are presented as number (%) or median (interquartile range)..
TASC, TransAtlantic Inter-Society Consensus; FP, femoropopliteal; PARC, Peripheral Academic Research Consortium; ABI, ankle-brachial index..
aData available in 32 limbs..
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Table 3 . Operative characteristics.
Variable Value (n=37) Diameter of PTFE graft 6 mm 3 (8.1) 7 mm 34 (91.9) Inflow arteries External iliac artery 2 (5.4) Common femoral artery including patch 34 (91.9) Superficial femoral artery 1 (2.7) Sites of combined inflow procedures 16 (43.2) Iliac artery 3 Common femoral artery 5 Both iliac and common femoral arteries 8 Details of combined inflow procedures Common femoral artery endarterectomy 9 Iliac artery stenting 5 Femoro-femoral bypass 5 CFA interposition graft 1 Outflow arteries Below-knee popliteal artery 26 (70.3) With distal modification 13 Without distal modification 13 Tibial arteries 11 (29.7) With distal modification 11 Combined outflow procedures 5 (13.5) Endarterectomy of below-knee popliteal artery 3 Balloon angioplasty of peroneal artery 2 Postoperative ABI of affected limba 0.95±0.15 Values are presented as number (%), number only, or mean±standard deviation..
PTFE, polytetrafluoroethylene; CFA, common femoral artery; ABI, ankle-brachial index..
aData available in 30 limbs..
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Table 4 . Risk factors for loss of primary patency: results from univariable and multivariable Cox analysis.
Variable Univariable analysis Multivariable analysis HR (95% CI) P-value aHR (95% CI) P-value Sex, male 2.23 (0.29-17.25) 0.444 Age 0.93 (0.86-1.01) 0.087 CLTI 0.53 (0.11-2.58) 0.429 Previous ipsilateral revascularization 3.44 (0.75-15.68) 0.111 Previous FP revascularization 4.09 (0.90-18.60) 0.068 3.91 (0.86-17.79) 0.078 TASC D vs. C 1.30 (0.29-5.90) 0.733 Poor runoff (0/1 vs. 2/3) 3.80 (1.14-12.69) 0.030 3.63 (1.09-12.08) 0.036 PARC severe calcification 0.87 (0.19-3.98) 0.857 Distal anastomosis (BKPA vs. tibial artery) 1.22 (0.34-4.46) 0.759 Distal modification 2.49 (0.73-8.54) 0.148 Adjunctive inflow procedures 1.39 (0.46-4.17) 0.561 Adjunctive outflow procedures 1.07 (0.14-8.35) 0.953 Hypertension 0.87 (0.28-2.72) 0.813 Diabetes mellitus 0.97 (0.32-2.97) 0.957 Coronary artery disease 2.57 (0.69-9.60) 0.161 Congestive heart failure 1.58 (0.34-7.31) 0.557 Cerebrovascular disease 0.83 (0.22-3.13) 0.788 COPD 0.65 (0.08-5.10) 0.681 Renal insufficiency 1.77 (0.54-5.85) 0.346 Dialysis 1.14 (0.14-9.10) 0.904 Dyslipidemia 1.94 (0.64-5.87) 0.243 HR, hazard ratio; CI, confidence interval; aHR, adjusted hazard ratio; CLTI, chronic limb-threatening ischemia; FP, femoropopliteal; TASC, TransAtlantic Inter-Society Consensus; PARC, Peripheral Academic Research Consortium; BKPA, below-knee popliteal artery; COPD, chronic obstructive lung disease..
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