Overall, 383 patients underwent EVAR between 2007 and 2016. Among them, 317 (82.8%) had EVAR performed within, and 66 (17.2%) had EVAR performed outside the IFU guidelines. Of the outside-IFU patients, 14 (21.2%) had short neck length, 27 (40.9%) had greater neck angulation, 9 (13.6%) did not meet neck diameter criteria, and 28 (42.4%) did not meet iliac diameter criteria.
Among all patients, 99 (25.8%) had T2ELs. Median follow-up duration was 39 months (interquartile range=18–69 months) in the T2EL group, whereas, it was 19 months (interquartile range=3–51 months, P<0.001) in the control group. Among 99 patients, 14 were excluded: 9 of them had T2ELs simultaneously with other types of endoleaks, 2 had T2ELs that occurred following other types of endoleaks, and 3 of them were lost to follow-up. Finally, 85 patients (22.2%) were categorized as having initial pure T2ELs (Fig. 1). Among them, 63 patients (74.1%) were classified as early T2EL patients (T2EL occurred before six months from operation) and 22 patients (25.9%) were classified as late T2EL patients (T2EL occurred after six months from operation). Among 63 patients, 52 (82.5%) early T2EL patients showed persistent T2EL after six months from occurrence.
In this study, male:female ratio was significantly higher in the control group than in the T2EL group. The higher number of patent LAs and lesser thickness of mural thrombi were significant risk factors for T2ELs. Patients with T2ELs had a mean of 6.16 patent LAs, whereas, patients without T2ELs had a mean of 5.48 patent LAs (P=0.001). IMA patency was found to have no association with T2ELs (Tables 1, 2). We additionally analyzed the relationship of IMA-related T2EL with IMA patency. Total number of IMA-related T2EL patients was 18, and the patients with patent IMA had more chance of IMA-related T2EL incidence. However, it did not show statistical significance (5/59 vs. 13/324, P=0.172).
Among the 85 patients with pure T2ELs, sac expansion during the follow-up period was detected in 29 patients (34.1%). The sac diameter showed no significant changes in 39 patients (45.9%), and the sac diameter decreased in 17 patients (20.0%) (Fig. 1). Median follow-up duration was 59.5 months (interquartile range=39–92.5 months) in sac expansion group, and 27 months in the others (interquartile range=16–56 months, P<0.001). However, adjusted median follow-up duration before sac expansion in sac expansion group was similar with the others (22.5 months, interquartile range=12–37.75 months; P=0.227).
Follow-up frequency was increased in the sac expansion group. In these patients, follow-up CT scan was performed at 3-month intervals. Among them, the T2ELs continued during follow-up period in 21 patients. However, the T2ELs resolved spontaneously or after additional treatment in 8 patients. Among the patients whose T2ELs were resolved, 5 had received treatment and 3 had their T2ELs resolved without treatment. The size of aneurysm sac decreased following the resolution of T2ELs in these patients. Among the 29 patients in sac expansion group, 5 patients developed other types of endoleaks. The T2ELs in these patients were early and persistent, which remained for more than two years, except in 1 patient who had spontaneously resolved T2EL 15 months after occurrence. In another 4 patients who had ongoing T2ELs, the aneurysm sacs expanded gradually at 3.5±1.5 mm/year. Other types of endoleaks occurred 62.5±27.4 months after operation. Two patients had type Ia endoleaks, and 3 patients had type Ib endoleaks (Fig. 2). Type I endoleaks were initially suspected in CT scan, and then, diagnostic angiography was performed. In the cases where type I endoleak was confirmed on angiography and was treatable, therapeutic intervention was performed simultaneously. In one case of type Ia endoleak that was not resolved by endovascular treatment, open surgical repair including aneurysm sac exploration and neck banding was performed. Other type Ia endoleak patients were treated with aortic cuff insertion and sac embolization. Three patients with type Ib endoleak underwent limb extension with or without internal iliac artery embolization [9,10]. Among the 3 patients, T2EL disappeared spontaneously in one patient 15 months after operation and regression of aneurysm sac was observed in follow-up CT scan. However, common iliac artery diameter enlarged gradually, regardless of sac regression, and type Ib endoleak occurred 4 years after operation.
Among the 39 patients in whom the sac size did not change, 3 patients underwent additional procedures for T2ELs because other types of endoleaks were not ruled out. They were treated with IMA and LA embolization. Among 36 untreated patients, the T2ELs were ongoing in 29 patients during the follow-up period. In 17 patients, sac size decreased despite their persistence of T2ELs. None of the 17 patients underwent additional interventions, and the endoleaks spontaneously disappeared in 6 patients. The other types of endoleaks did not occur in patients whose sac size was reduced or remained unchanged (Fig. 3).
Tables 3 and 4 show the demographic characteristics and anatomical features that were compared among the groups classified by sac size change. An increase in sac size was found to be more frequent among patients with underlying hypertension (P=0.05). Patients who showed sac expansion had a mean of 6.82 patent LAs, and patients who did not show sac expansion had a mean of 5.7 patent LAs (P=0.003). IMA patency was not a risk factor for sac expansion. Preoperative maximal sac diameter was suspected to be associated with increase in sac size, but it was not a statistically significant risk factor. None of the T2EL patients experienced rupture during follow-up.
Among 85 patients with initial pure T2EL, 15 patients (17.6%) showed spontaneous resolution. The sac size remained unchanged in 9 patients and regressed in 6 patients. We additionally identified the factors associated with spontaneous resolution of T2EL. Number of LAs was higher in the ongoing endoleak group; however, it did not reach statistical significance. Non-smokers and patients with coronary artery disease (CAD) seemed to have more chance of ongoing endoleak; however, it also failed to achieve statistical significance (Table 5).