Popliteal artery aneurysms. Factors associated with thromboembolism and graft failure.

Aim: The purpose of this study was to review our experience with popliteal artery aneurysms (PAAS) and to identify the major factors associated with thromboembolism of PAAS and failure of grafts after surgical repair.

Methods: The medical records of 38 patients with 42 PAA, who presented in a university medical center between March 1985 and September 2000, were retrospectively reviewed. Data were collected on clinical presentation, risk factors, type of reconstructions, early and late morbidity, limb loss and mortality. Duplex scan, as well as computed tomography, was performed in 33 (78.6%) cases, and preoperative angiography in 38 (90.5%). Thrombolysis was performed prior to surgical reconstruction (16.07+/-21.97 months) in 4 cases presented with acute ischemia. All patients underwent synthetic (23, 54.8%) or autogenous (19, 45.2%), below-the-knee (39, 92.9%) or above-the-knee (3, 7.1%) femoropopliteal bypass graft. The proximal and distal anastomoses were end-to-end both in both cases in 30 bypasses (71.4%). Thirty-six (86%) aneurysms were surgically treated by one vascular surgeon. Postoperative anticoagulants were given in 8 cases (19%). Long-term follow-up (mean: 57.59+/-37.77 months) was available for 35 patients (92.1%). Multivariate analysis was used to assess association between risk factors and outcome.

Results: Thirty-five patients were males, 3 were females; mean age was 68.31+/-8.66 years. Risk factors were arterial hypertension (25, 69%), smoking (19, 50%), dyslipidemia (7, 18.4%) and diabetes (5, 13.2%). Thirty PAAS (71.4%) were symptomatic for acute (11, 26.2%) or chronic (7, 16.7%) ischemia, distal embolization (8, 19%), compression of the popliteal fossa (3, 7.1%) and rupture (2, 4.8%, one of which presented with acute ischemia); 12 were asymptomatic. Bilateral PAAS were present in 18 patients (47.4%); 14 (36.8%) also had an abdominal aortic aneurysm (AAA); associated AAAS were twice as common in patients with bilateral PAAS (9/18, 50%) compared to those with unilateral PAAS (5/20, 25%; p=NS). The mean diameter of the PAAS was 3.4 cm; no significant difference was found in the mean diameter of symptomatic and asymptomatic aneurysms. Complete thrombosis of the aneurysmal sac was found in 15 cases (35.7%), severe atherosclerotic femoro-popliteal lesions in 17 (40.5%), arteriomegaly in 11 (26.2%), occlusion of the superficial femoral artery (SFA) in 7 (16.7%). Three leg arteries were present in 17 limbs (40.5%), 2 in 6 (14.3%), 1 in 7 (16.7%), no leg vessels in 12 (28.6%). Occlusion of the SFA and the absence of major leg arteries were independently associated with thrombosis of the aneurysmal sac (p=0.005). Two-thirds of patients with thrombosed PAA (10, 66.7%) presented with acute ischemia, while 1/3 (5, 33.3%; p=NS) had some degree of claudication. Optimal runoff (score=1) was estimated in 23 limbs, while score was between 2-7 in 19 limbs. Thrombolysis was successful in all 4 cases, with no complications. Primary graft patency was 66.1% at 4 years; the only variables independently associated with loss of bypass patency were smoking (p=0.04) and poor leg runoff (p=0.02). Postoperative bypass occlusion occurred in 2 cases presented respectively with acute and chronic ischemia, and in 2 asymptomatic patients; all 4 bypasses were polytetrafluoroethylene grafts. A total of 8 thrombosed, polytetrafluoroethylene, below-the-knee bypass grafts required secondary reconstructions (2 redo + 6 restorative procedures). The secondary patency rate at 3 years was 77.9%. Lower limb amputation had to be performed 2 months after primary reconstruction in 1 case (2.4%) presented with acute ischemia. The estimated limb salvage rate at 10 years was 96%. Mortality was 4.8%. Survival at 6 years was 82.6%.

Conclusion: Our experience indicates that SFA occlusion and poor runoff vessels were independent factors associated with PAA thrombosis. The diameter of asymptomatic PAAs was not significantly different than that of asymptomatic ones. Use of tobacco and poor runoff vessels were independent factors associated with primary bypass patency. In PAAs complicated with acute ischemia, thrombolysis allowed us to regain a good runoff and to perform subsequent bypass procedure, with no amputation. The use of autogenous graft material, when possible, is recommended.