Comparing the safety and efficacy of endovascular treatment versus bypass surgery for infrarenal aortic occlusion: a single-center experience

Infrarenal aortic occlusion (IAO) is a complete occlusion of infrarenal aorta, which is the most complicated and severe subclass of aortoiliac occlusive disease(AIOD). The first-line treatment for IAO is bypass surgery due to its favorable patency rate. As endovascular technique advances, several retrospective studies have reported their endovascular experience for IAO. However, whether endovascular treatment(EVT) is comparable to bypass surgery for IAO required further study. This research was to study the safety and efficacy of EVT for IAO compared to bypass surgery.


Conclusions
The safety and efficacy of EVT were comparable to that of anatomic bypass surgery for IAO. EVT could be a feasible option for IAO.

Background
Infrarenal aortic occlusion(IAO) is a complete occlusion of infrarenal aorta, which classifies as TransAtlantic Inter-Society Consensus(TASC II) Type D lesions (1). It is the most complicated and severe subclass of aortoiliac occlusive disease(AIOD). Symptoms of IAO include intermittent claudication, loss or weakening of femoral artery beats, and erectile dysfunction in male patients (2).The incidence of IAO is low(prevalence, 0.15%)(3), accounting for only 3% ~ 8.5% of AIOD(4). The TASC II guidelines recommended bypass surgery for IAO due to its favorable primary patency rates (1). As endovascular technique advances, several groups have reported case series about their endovascular experience for IAO(5-9). In 2017, the European Society for Vascular Surgery(ESVS) proposed that endovascular treatment(EVT) could be first-line therapy for severe cases of AIOD who could not tolerate surgery. For patients who could tolerate surgery, aortofemoral bypass surgery was recommended, and EVT was an alternative(10). However, it remains unknown whether the safety and efficacy of EVT for IAO are comparable to that of bypass surgery.
This study reviewed a total of 44 IAO patients treated surgically at PUMCH center retrospectively, and the patients were divided into EVT group and aortofemoral bypass group, to compare the safety and efficacy of EVT versus bypass surgery for IAO.

Inclusion and exclusion criteria
Inclusion criteria: 1.This study included all the consecutive patients with chronic(duration>6 months) and atherosclerotic total infrarenal aortic occlusion, who were treated surgically as inpatient The left brachial artery was punctured, a catheter combined with a guidewire passed through the aortic arch and the descending aorta to the abdominal aorta. Then the surgeon replaced the catheter with a 6/7F 90cm long sheath. The catheter, along with the 0.035 or 0.018 guidewire, was delivered through the occlusive segments to the true lumen of the femoral artery. The femoral arteries were punctured, a short sheath implanted, and the working guidewire reestablished through the sheath side by side. The surgeon predilated the occlusion segments of the abdominal aorta and the iliac artery using a balloon (for example, Reekross 4-120 mm), and implanted two stents(for example, Medtronic 8*100, 8*120 mm) along with the guidewire by kissing technique. If the lesion was not covered completely, a stent of suitable length implanted jointly. Then we expanded the occlusive part again inside the stents with a balloon(for example, ADMIRAL 6*80 mm or longer). The detailed information was shown in Supplementary 1 Table 1; the specific stent type depended on the surgeon's preference and the lesion. After that, the surgeon performed angiography to confirm blood flow and apposition of the stents.
Aortofemoral bypass: Surgeries were performed under general anesthesia using a transperitoneal midline incision and longitudinal inguinal incision to expose the abdominal aorta and the femoral arteries, respectively. After heparinization, the surgeon clamped the abdominal aorta at a suitable level according to the upper edge of the occlusion. If renal arteries were involved, then they needed to be clamped as well. The surgeon cut the abdominal aorta, 2cm below the level of the renal artery and then stripped out the thrombus. A bifurcated artificial graft (GORE-TEX 16-8mm) was employed retroperitoneally, and an end-to-side anastomosis at the aorta and femoral artery were performed with Prolene3-0 or 5-0,respectively.

Data analyses
Quantitative data are described as mean and compared by independent t-tests.
Categorical data are summarized as frequency and compared by chi-square tests. Ordinal categorical data are compared by the rank-sum test. The curve of the accumulative probability of survival was determined by the Kaplan-Meier method. P values were all twosided, and statistical significance was defined as P .050. All statistical analyses were performed by using GraphPad Prism (5.0v; GraphPad Software Inc).

Follow up
All cases were followed up at 0 months, 6 months, and 12 months postoperatively.
Duration of follow-up was the period from the surgery to the last outpatient visit.
Technical success was defined as revascularization of the occluded artery, and clinical success was defined as Rutherford classification returned to class 0. The surgeon reevaluated the symptoms, artery pulses of the lower limb, and ankle-brachial index (ABI).
Symptom-free was defined as the no aggregation of claudication, no loss of previous palpable pulse and no decrease in ABI( 0.15) compared to the best post-operative condition.
catheter-directed thrombolysis before EVT, and then acute renal infarction occurred(Cr 146mmol/L). The patient was discharged with conservative treatment. However, due to the small sample size, there was no statistical difference in the technical success rate between the three groups (P>0.05). The 2 severe complications in the EVT group were acute kidney failure and retroperitoneal hematoma, respectively; the 7 severe complications of the aortofemoral bypass group were severe atrial fibrillation, severe pneumonia, infection of the graft, anaphylactic shock due to anesthesia, severe acute coronary syndrome, acute anterior myocardial infarction combined with pneumonia, massive pleural effusion with postoperative intestinal obstruction, respectively. The proportion of serious complications in EVT the group was less than that of the bypass group (12.5%(2/16) in the EVT group, 25%(7/28) in the aortofemoral bypass group), but there was no statistical difference due to the small sample size (Table 3.). A representative example of the EVT procedure was shown in figure 1. The duration of hospital stays was 4 days for the EVT group, 11 days for the bypass group (Table 3.). There was a significant difference in hospital stay between the EVT group and the bypass groups (P<0.05).
Follow-up 40 out of 44 patients had an effective follow-up after surgery. The median follow-up period was 50.9 months. 31 out of the 40 patients' symptoms disappeared after the operation and reached an asymptomatic state (Table 3). The 1-year, 3-year, and 5-year cumulative symptom-free survival rates were 85.7%, 85.7% and 85.7% in the EVT group, 100%, 94.1% and 80.7% in the aortofemoral bypass group. There was no significant difference in symptom-free survival rate between the two groups according to the log-rank test(P=0.92) (figure 1). The evaluation of primary and secondary patency was not conducted because a majority of asymptomatic patients had not performed any imaging examinations after surgery.

Discussion
Aortofemoral bypass has been performed to treat IAO since the 1960s; it is still the firstline treatment of IAO nowadays. Recent meta-analysis showed that the perioperative mortality rate is 0%-1.9%(11). Surgical techniques have developed to reduce ischemic damage of kidney in proximal IAO (11, 12). Recent research shows that its 5-year patency rate is 88.6%(4). In our center, 20 of 24 patients returned to the asymptomatic state, and the accumulative probability of survival was 80.7% for 5 years. Also, there was no perioperative death in our study, but 25% (7/28) patients had life-threatening complications. Suggesting that comprehensive evaluation is necessary to select patients who can tolerate the bypass surgery.
With rapid development of EVT, the guideline has recommended EVT as the preferred treatment for short stenosis or short occlusion of the iliac artery segment (types A and B in the TASC grading)(1). Unlike type A and B, IAO(type D) involves the problems about the establishment of guidewire pathways. If a recanalization cannot be established, EVT cannot be performed. In order to increase the success rate of establishing working pathways, "double-barrel" self-expanding stents(13), catheter-directed thrombolysis and even hybrid surgery can be used. As in our EVT group (n=16), 4 patients did catheterdirected thrombolysis, and 2 patient performed femoral endarterectomy as an adjunctive treatment (Supplementary 1 Table 1). For extensive stenosis or occlusion of the aortoiliac artery (TASC grading, types C and D), a recent meta-analysis shows that EVT also has a technical success rate of 90% and a one-year primary patency rate of nearly 90%(14).
Cases of EVT for IAO have been reported in the early 1990s (15,16), and more case series study has appeared in recent years(6, 8,9,17,18). A cases series including 49 IAO patients treated with EVT reported the primary patency rate was 88.4% at 1 year and 80.1% at 3 years(6). Another case series including 31 IAO patients reported the primary patency rates were 85% and 66% at 1 and 3 years, respectively(5). As more and more data have shown satisfied outcomes of EVT for treating IAO, whether EVT is comparable to the first-line aortofemoral bypass surgery required to be answered. And this study proved that EVT is as safe and effective as compared to aortofemoral bypass surgery.
Our study had several limitations. It was a retrospective study; the patients were divided nonrandomly into EVT group and bypass group. Moreover, the small sample size of our study also limited statistical comparisons.

Conclusions
We reported a retrospective study of EVT or bypass treated IAO in our center. The demographics and preoperative Rutherford classifications were equally distributed in the two groups. Technical success rate, mortality rate, complications rate, and Rutherford classification after procedures, and 1-year, 3-year and 5-year symptom-free survival proportion were compared between the 2 groups, and there was no significant difference between the 2 groups. Therefore, the safety and efficacy of EVT for IAO is comparable to that of bypass surgery, and EVT could be a feasible choice for the treatment of IAO patients.     Asymptomatic survival curve in patients who were asymptomatic after procedures. (EVT group n=11, aortofemoral bypass group n=20).

Supplementary Files
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