Abstract

Background. Data are limited regarding the efficacy of percutaneous mechanical thrombectomy (PMT) for the treatment of acute lower extremity (LE) ischemia. The current study was undertaken to evaluate the results following PMT for occluded LE bypass grafts, stents, and thromboembolic events involving native arteries. Methods. During a 3-year period, 43 patients underwent PMT. The patient’s outcome, including the technical success rate, additional procedures, major complications, limb salvage rate, and length of hospital stay were documented for each patient. Ultrasound follow up with clinical correlation was performed at 6 weeks and 3, 6, 12, 18, and 24 months. Results. PMT was performed for occluded synthetic bypass grafts (n = 18), vein bypass grafts (n = 6), stents (n = 4), and native arterial vessels (n = 15). The immediate technical success rate was 28% (n = 12). Twenty-one (49%) patients required adjunctive catheter-directed thrombolysis (CDT) for success. Additional endovascular procedures were performed in 30 patients (70%), with a resulting overall success rate of 77% (n = 33). The mean hospital stay was 7.2 days. A major bleeding complication occurred in one patient. In order to maintain patency during the first-year, follow-up patients required additional endovascular and or open vascular procedures. For all patients, the 6-week, 6-month, and 1-year ankle brachial index was 0.93, 0.88, and 0.95, respectively. The one-year limb salvage rate was 88%. Conclusion. PMT is a safe and effective treatment for acute lower extremity ischemia. PMT with combined CDT is associated with a high success rate and acceptable limb savage rate at one year.

Introduction

Acute lower extremity ischemia (ALI) most commonly results from thromboembolic occlusion of lower extremity arteries and bypass grafts. Open surgical thrombectomy provides rapid removal of thrombus and the restoration of blood flow, and has traditionally been the treatment of choice for ALI.1 The success of thrombolytic therapy with percutaneous catheter-directed thrombolysis (CDT) has also been demonstrated.2–4 In selected patients, CDT may provide effective treatment for ALI and reduce morbidity, compared to open surgical thrombectomy.

Percutaneous mechanical thrombectomy (PMT) has emerged as another minimally invasive option for the management of acute arterial and venous thrombus. PMT may provide stand-alone therapy for ALI or, more commonly, is used in combination with thrombolytic therapy. Although several reports have described the safety and efficacy of PMT in the peripheral circulation, the utility as a first-line therapeutic option for ALI has not been defined.5–9

The current study was undertaken to evaluate the immediate and long-term results following PMT for thromboembolic occlusion of bypass grafts, stents, and native arteries in the lower extremities.

Patients and Methods

A retrospective review identified 43 patients at our institution that underwent PMT for ALI between January 2004 and July 2007. Six vascular surgeons performed all procedures using the AngioJet Xpeedior (Possis Medical, Minneapolis, Minnesota) thrombectomy catheter. Only patients with acute occlusions (< 48 hrs) were included. Patients with contraindications to thrombolytic therapy and those with severe motorsensory deficits were excluded.

After angiographic identification of the lesion, rheolytic thrombectomy using the Power-Pulse technique was performed. The Power-Pulse technique for acute lower extremity ischemia was performed as previously described by Allie et al.9 Initial technical success was defined as > 90% thrombus removal and return of distal pulses. Patients who did not achieve technical success received CDT. Follow-up angiography was performed within 12 hours. At this time, if resolution had not been obtained, patients had either repeat rheolytic thrombectomy, repeat CDT, conversion to open thrombectomy and/or bypass, or amputation, depending on the clinical findings of the extremity. During the course of treatment, patients also received angioplasty, stent placement, and laser artherectomy, as indicated by angiographic findings.

Patient demographics and clinical characteristics are presented in Table 1. The mean patient age was 63 years ± 25. There were 26 males and 17 females. Twenty-four patients presented with occluded bypass grafts. Six patients had occluded vein bypasses: femoral-popliteal (n = 4) and femoral-tibial (n = 2). Eighteen patients presented with occluded synthetic bypass grafts: femoral-popliteal (n = 11), femoral-tibial (n = 2), aorto-femoral (n = 2), femoral-femoral (n = 1), ilio-femoral (n = 1), and ilio-popliteal (n = 1). Four patients presented with occluded infrainguinal stents. There were 15 native vessel occlusions: femoropopliteal (n = 9), tibio-peroneal (n = 4), and iliac (n = 2).

Major complications, additional procedures, and hospital stay were recorded for each patient. Ultrasound follow-up with clinical correlation was performed at 6 weeks and 3, 6, 12, 18, and 24 months. The major endpoint included limb salvage rate at 1 and 12 months.

Results

The initial technical success rate for PMT was 28% (12/43). Twenty-one patients underwent successful adjunctive CDT to yield an overall success rate of 77% (33/43). Three (7%) patients required conversion to open thrombectomy and 4 patients required surgical bypass. Twenty-eight patients (65%) had angioplasty and/or stent placement and 2 (4%) underwent laser atherectomy during the initial therapeutic intervention. Table 2 demonstrates the number of successful outcomes, as well as the number of patients requiring CDT to achieve a successful outcome based on conduit type.

Between the initial procedure and 12 months postoperatively, 11 patients (26%) had additional vascular procedures performed to maintain patency, including graft revision, angioplasty/stent placement, laser atherectomy, and open thrombectomy. Primary patency at one year for native, PTFE, vein, and stent conduits were 80, 43, 20, and 100%, respectively (Table 2).

The major complication rate was 2%, with one person having a large retroperitoneal bleed. There were 2 perioperative deaths unrelated to vascular treatment. One patient had an ischemic CVA on postoperative day 1, and the other had a postoperative MI.

Five patients underwent amputation within 1 month, and 3 additional patients had amputations at 1 year (Figure 1). The calculated 1-month and 1-year limb salvage rates were 88% and 81%, respectively (Table 2). Mean length of hospital stay was 7.2 days (n = 35). For patients who only underwent PMT, the average hospital stay was 4.3 days (n = 16). The mean ABI (ankle brachial index) at 6 weeks, 3, 6, 12, 18, and 24 months was 0.93, 0.90, 0.88, 0.95, 0.90, and 0.79, respectively (Figure 2).

Discussion

PMT has gained popularity as an alternative to open thrombectomy for the management of acute arterial thrombus. Previous reports have demonstrated immediate restoration of antegrade blood flow in more than 90% of patients undergoing PMT.5,6,8,10 Although the immediate technical success rate in our study was only 28%, antegrade blood flow was re-established in a majority of patients at the initial intervention. We defined technical success as > 90% thrombus removal, which was achieved in 77% of our patients with the addition of CDT.

In prior reports evaluating the mean lysis time between PMT and CDT alone, studies favor PMT to produce a more rapid revascularization, however, it was noted that PMT had a great incidence of incomplete thrombus removal, with further need for CDT.9 A majority of our patients required adjunctive CDT for complete thrombus removal. In addition, most patients with thrombosed grafts required treatment for the underlying stenosis or occlusion responsible for graft failure. All of our cases were performed in a surgical/endovascular suite, and this provided the appropriate imaging and equipment for a variety of procedures. More than 28% of the patients in our study had angioplasty and stenting following PMT. Compared to open thrombectomy, the percutaneous treatment for ALI is more often multi-modal and should be performed in a setting that allows for easy transition from PMT to other complex endovascular therapies. Finally, our surgical/endovascular suite also allowed for definitive management of those patients requiring conversion to open thrombectomy or fasciotomy.

Patients presenting with ALI require prompt and definitive treatment to reduce morbidity and prevent limb loss. A goal of our study was to identify certain patient characteristics that were capable of predicting success of PMT. We looked at the type of conduit used, the location of the occlusion, and the use of additional thrombolysis, angioplasty, and/or stenting.
Unfortunately, due to the small sample size, we failed to identify any statistically significant clinical variables that predicted success. It should be noted that PMT performed for stents appeared to have excellent short- and long-term results, again. However, we are unable to give a definitive statement due to such a small sample size. The results overall were similar, regardless of the type of bypass, location of the thrombus, or involved the native circulation. We had expected to observe better outcomes with synthetic grafts secondary to the uniformity of grafts, compared to the native circulation and vein bypasses. In addition, percutaneous thrombus removal may be hindered in vein grafts secondary to retained valves, which are not found in prosthetic grafts. Perhaps a difference would be demonstrated with a larger study group.

PMT and CDT were successful in restoring patency in a majority of the patients; however, maintaining patency often required additional procedures. Eleven patients (27%) underwent subsequent endovascular and/or open vascular intervention to maintain patency within the first year. These interventions were successful in preventing a second thrombotic event and helped maintain a mean ABI of greater than 0.9 at 12 months. As expected, patency was directly related to limb salvage (81% at 1 yr) in our patients. Our limb salvage rate is similar to that reported in previous series describing open thrombectomy, and appears acceptable in this difficult group of patients.6,8,10

Complications were infrequent in our study. One patient developed a significant retroperitoneal bleed that was managed conservatively without operative intervention. We experienced no additional bleeding complications despite the use of CDT. There have been concerns regarding anaphylactic reactions, renal dysfunction, and embolic complications with the AngioJet system. However, we did not observe these in our study.

Limitations of this study include our relatively small sample size. In addition, we did not have an adequate number of patients for accurate long-term follow up. The study will be ongoing, with the addition of patients and the updating of current patient data until definite conclusions can be made.

Summary

The current study demonstrates that PMT is a safe and effective treatment for acute lower extremity ischemia. PMT combined with CDT is associated with a high technical success rate and acceptable limb savage rate at one year.