Treatment of type II endoleaks with a novel polyurethane thrombogenic foam: induction of endoleak thrombosis and elimination of intra-aneurysmal pressure in the canine model.

OBJECTIVE: The clinical significance and treatment of retrograde collateral arterial perfusion of abdominal aortic aneurysms after endovascular repair (type II endoleak) have not been completely characterized. A canine abdominal aortic aneurysm model of type II endoleak with an implanted pressure transducer was used to evaluate the use of polyurethane foam to induce thrombosis of type II endoleaks. The effect on endoleak patency, intra-aneurysmal pressure, and thrombus histology was studied. METHODS: Prosthetic aneurysms with an intraluminal, solid-state, strain-gauge pressure transducer were created in the infrarenal aorta of 14 mongrel dogs. Aneurysm side-branch vessels were reimplanted into the prosthetic aneurysm of 10 animals by using a Carrel patch. Type II (retrograde) endoleaks were created by excluding the aneurysm from antegrade perfusion with an impermeable stent graft. Thrombosis of the type II endoleak was induced by implantation of polyurethane foam into the prosthetic aneurysm sac of four animals. Six animals with type II endoleaks were not treated. In four control animals, no collateral side branches were reimplanted, and therefore no endoleak was created. Intra-aneurysmal and systemic pressures were measured daily for 60 to 90 days after the implantation of the stent graft. Endoleak patency and flow were assessed during surgery and at the time of death by using angiographic imaging and duplex ultrasonography. Histologic analysis of the intra-aneurysmal thrombus was also performed. RESULTS: Intra-aneurysmal pressure values are indexed to systemic pressure and are represented as a percentage of the simultaneously obtained systemic pressure, which has a value of 1.0. All six animals with untreated type II endoleaks maintained patency of the endoleak and side-branch arteries throughout the study period. Compared with control aneurysms that had no endoleak, animals with patent type II endoleaks exhibited significantly higher intra-aneurysmal pressurization (systolic pressure: patent type II endoleak, 0.702 +/- 0.283; control, 0.172 +/- 0.091; P < .001; mean pressure: endoleak, 0.784 +/- 0.229; control, 0.137 +/- 0.102; P < .001; pulse pressure: endoleak, 0.406 +/- 0.248; control, 0.098 +/- 0.077; P < .001; P < .001 for comparison for all groups by analysis of variance). Treatment of the type II endoleak with polyurethane foam induced thrombosis of the endoleak and feeding side-branch arteries in all four animals with type II endoleaks. This resulted in intra-aneurysmal pressures statistically indistinguishable from the controls (systolic pressure, 0.183 +/- 0.08; mean pressure, 0.142 +/- 0.09; pulse pressure, 0.054 +/- 0.04; not significant). Angiography and histology documented persistent patency up to the time of death (mean, 64 days) for untreated type II endoleaks and confirmed thrombosis of polyurethane foam-treated endoleaks in all cases. CONCLUSIONS: Untreated type II endoleaks were associated with intra-aneurysmal pressures that were 70% to 80% of systemic pressure. Treatment with polyurethane foam resulted in a reduction of intra-aneurysmal pressure to a level that was indistinguishable from control aneurysms that had no endoleak. CLINICAL RELEVANCE: Endovascular repair of abdominal aortic aneurysms is dependent on the successful exclusion of the aneurysm from arterial circulation. Type II endoleaks originate from retrograde flow into the aneurysm sac. This study demonstrates the use of polyurethane foam to induce thrombosis in a canine model of a type II endoleak, thereby reducing intra-aneurysmal pressure to levels similar to levels in animals without endoleaks. This approach may be a strategy for future treatment of type II endoleaks.

Percutaneous endovascular treatment for chronic limb ischemia.

Percutaneous transluminal methods of revascularization for chronic limb ischemia have traditionally been used as an adjunctive or secondary mode of treatment. This study examines the outcomes of patients treated via endovascular methods as the primary form of treatment. The records of 66 patients (average age, 71.3 years; range, 53 to 92) with chronic limb ischemia treated from November 2000 to January 2002 at a single institution with endovascular methods were retrospectively reviewed. Thirty-one patients had disabling claudication, 15 had rest pain, 17 had minor tissue loss, and 3 had major tissue loss. There were 94 lesions in the 66 limbs: 45 lesions in the superficial femoral artery, 28 lesions in the popliteal artery, and 21 lesions in tibial arteries. Occlusive lesions were treated by subintimal angioplasty. Stenoses were treated by percutaneous transluminal angioplasty (PTA). The median length of the lesions was 12 cm. Forty-six stents were placed in 32 patients; 34 patients did not receive stents. The approach was contralateral in 71% (47/66) and ipsilateral in 29% (19/66) of cases. Patients were followed up with physical exam, anklebrachial index (ABI), and duplex ultrasonography. Post-intervention medical treatment included aspirin and clopidogrel. Long-term patency was correlated with age, comorbidities, risk factors, and the use of stents in addition to angioplasty. Endovascular treatment was technically successful in 65 of 66 patients (98%). Residual stenosis (<30%) was found in three cases, two in patients with PTA alone and one patient with PTA and a stent. Mean length of follow-up was 6.3 months (range, 6 weeks to 15 months). Post-intervention ABI improved from a mean of 0.65 to a mean of 1.01 (p < 30.05). The perioperative complication rate was 9% and included three cases of hematoma and one case each of thrombosis, lymphocele, and rash reaction to medications. Outcome measures included primary patency (89%), assisted primary patency (96%), and limb salvage (97%) at 6 months. Restenosis of >50% occurred in four patients and occlusion occurred in two. At 6 months, patients with one or more stents had a patency rate of 84% (27/32), whereas those without a stent had a patency rate of 94% (32/34) (p = NS). Endovascular treatment is a safe, feasible, and effective method with a high short-term patency rate and may be used as an alternative to bypass for chronic limb ischemia.

Failure of endovascular aortoaortic tube grafts: a plea for preferential use of bifurcated grafts.

OBJECTIVE: Aortoaortic tube graft repair was the first technique used for the endovascular treatment of abdominal aortic aneurysms (AAAs). However, progressive changes in the morphology of the distal aortic neck may be responsible for procedural failure. This study examines the use of aortoaortic tube prostheses and analyzes the factors that contributed to their failure and the methods used for their subsequent repair. METHODS: During a 7-year period, 462 patients with abdominal aortic aneurysms underwent endovascular aortic aneurysm repair. Of these, 65 patients (14%) underwent treatment with aortoaortic tube endoprostheses. Aortoaortic tube prostheses used included Talent (n = 44) (Medtronic-Worldmedical, Sunrise, Fla), Vanguard (n = 8) (Boston Scientific, Natick, Mass), EVT/Ancure (n = 4) (Guidant, Menlo Park, Calif), and physician-fabricated (n = 9). All the tube graft procedures were performed in the operating room with fluoroscopic guidance. The average age of patients for aortoaortic tube grafts was 74.5 years, and 48 of the patients were men. Failure was defined as aneurysm expansion, any type I endoleak, or type II endoleak persistent after 6 months. RESULTS: No aneurysm ruptures or perioperative deaths were seen. Retrograde aneurysm perfusion from lumbar or inferior mesenteric arteries (type II endoleak) that persisted beyond 6 months was present in three patients. Proximal attachment site endoleaks were present in two patients. No distal implantation site endoleaks were present within 1 month of the initial endovascular repair; however, endoleaks at the distal attachment site developed in 12 patients subsequently and included all graft types (Talent, n = 6; Vanguard, n = 2; Ancure/EVT, n = 1; physician-fabricated, n = 3). The average time interval to failure was 12.9 months. Preoperative distal aortic neck length showed a significant correlation with the subsequent development of distal endoleak (endoleak, 16.6 +/- 6.8 versus no endoleak, 23.3 +/- 9.6; P =.03). Preoperative distal aortic neck diameter, however, did not show significance (23.8 +/- 5.2 versus 22.6 +/- 4.7; P = not significant). CONCLUSION: Endovascular aortoaortic tube grafts are vulnerable to failure even when initial exclusion of the aneurysm is successful. A significant association is seen between distal neck length and eventual failure. Because of the propensity toward eventual failure, the use of aortoaortic tube grafts in the infrarenal aorta cannot be recommended for typical fusiform aneurysms, even when an adequate distal neck appears to be present.