Catheter-directed thrombolysis versus percutaneous mechanical thrombectomy in the management of acute limb ischemia: a single center review

Acute limb ischemia (ALI) is defined as a sudden significant decrease in limb perfusion that has been present for less than 14 days that is causing a threat to limb viability (Patel et al., 2003). To preserve viability and to reduce mortality and morbidity, early restoration of blood flow is crucial. This can be achieved by various surgical or endovascular techniques depending on the severity (Norgren et al., 2007).

Catheter directed thrombolysis (CDT) has been the first line treatment for acute limb ischaemia since the STILE and TOPAS trials in the 1990s (The STILE investigators, 1994; Ouriel et al., 1996). CDT is currently indicated in patients who do not have contraindications and who fall under I and IIA-IIB Rutherford classification categories (Byrne et al., 2014) for ALI. CDT requires long infusion times and close monitoring in an intensive care unit. Major risks of CDT include hemorrhage, including up to a 0.4% risk of potentially fatal intracranial haemorrhage when treated with Urokinase (Karnabatidis et al., 2011). Despite treatment, ALI is still associated with significant mortality (9–15%) and an amputation rate reaching 30% (Dormandy et al., 1999).

Due to these associated risks, percutaneous mechanical thrombectomy (PMT) devices have gained popularity. Some studies have supported the use of PMT as a first- line treatment option for ALI because this can reduce the procedure time and rapidly improve perfusion (Leung et al., 2015a).

We aim to compare the efficacy and safety profile of CDT and PMT in the management of acute limb ischemia.

This is a retrospective study approved by the institutional review board in a tertiary referral hospital. The data from 117 procedures performed in 94 patients between 2006 and 2015 was collected. Treatment choice (CDT or PMT) in every case was based on the clinical scenario and the operator’s expertise in PMT use.

Primary outcomes were technical and clinical success.

Technical success was defined as removal of 99% of clot.

Clinical success was defined as a return to premorbid Rutherford score without major amputation within 30 days.

The use of minor additional techniques to remove clots, such as balloon maceration and aspiration (without dedicated suction catheters), was considered part of the primary procedure in either group. Additional CDT after PMT or vice versa was deemed technical failure. The use of protective filter was not part of the treatment.

Secondary outcomes were amputation rate at 30 days, duration of hospitalization and 30-day mortality. The complications were recorded according to the CIRSE classification of complications (Filippiadis et al., 2017).

A total of 117 procedures were performed in 94 patients [mean age 65 years, 67% male (n = 63)]. Of the 117, 27 were surgical bypass grafts, 31 were previously stented arteries and 59 were native vessels. 28 procedures (24%) utilized PMT, and 89 (76%) procedures utilized CDT. Of the 28 procedures in the PMT group, 10 were performed with ROTAREX and 18 were performed with ANGIOJET.

Our study shows higher technical success in the PMT group compared to the CDT group (68% vs 47%). However, CDT in this cohort was used in more complex distal occlusive disease. This is likely because the use of PMT below the knee vessels is thought to be risky due to small calibre vessels in our population. Conversion of one treatment to another was only seen in 14% of patients in PMT group and 6% of patients in CDT group, hence, did not contribute much towards drop in technical success. The choice of treatment is also dependent on the operator’s experience and knowledge of thrombectomy devices. This selection bias is inherent to the retrospective nature of this study.

Few studies have demonstrated high technical success with PMT ranging between 56 and 95% (Karnabatidis et al., 2011). Kasirajan et al. investigated PMT using ANGIOJET in acute and subacute limb ischemia and divided technical success into failure (< 50% luminal restoration), partial success (50–95% luminal restoration) and complete success (> 95% luminal restoration). The complete success rate was 61.4% (Kasirajan et al., 2001).

Similarly, Byrne et al. demonstrated 90% technical success rate but they defined technical success as the restoration of inline flow to the foot without requiring immediate surgical intervention (Byrne et al., 2014), which is similar to our definition. However, we also attempted to quantify the clot burden and defined technical success as the removal of 99% of the clot.

Despite PMT being technically superior, the clinical success remains similar in the PMT and CDT groups (75% vs 73%) and PMT was also not a predictor for clinical success in the regression analysis.

The regression analysis showed that patients without end-stage renal disease had a tendency for higher clinical success. Patients with end-stage renal disease tend to have extensive vascular disease and revascularization can be challenging in such cases. Similar findings were reported by Byrne et al.; they reported a 6 to 26-fold increased risk of amputation and the loss of primary and secondary patency in patients with end-stage renal disease (Byrne et al., 2014).

As previously noted, the major limiting factor for CDT is hemorrhagic complications. Seven percent (n = 6) of patients receiving CDT in this study had major bleeding. Of these, 3 patients had groin access hematomas and 2 patients had gastro-intestinal bleeding. Seven percent (n = 2) of patients receiving PMT had major groin access hematomas; this difference was not statistically significant. None of the patients receiving CDT had a hemorrhagic stroke in our cohort. Karnabatidis et al. reported a 0.4% risk of potentially fatal intracranial hemorrhage when treated with Urokinase (Karnabatidis et al., 2011).

In this study, there was no significant difference in 30-day mortality between CDT and PMT (8% vs 4%, p = 0.425); this is comparable to the published data. Byrne et al. reported 30-day mortality in 4.8% of patients with CDT and 5.6% with PMT (p = 0.82) (Byrne et al., 2014).

The duration of hospitalization was significantly shorter in patients who underwent PMT; the mean stay was 6 days in PMT group vs 12.6 days in the CDT group, p = 0.0001. PMT was used more in category I and IIa patients with femoral and popliteal disease. The reduced technical success in the CDT group may have played a role in prolonging the hospital stay in this group. The mean duration of CDT was 12 h in this study; hence, this likely did not play a major role in the duration of hospitalization.

The thirty-day amputation rates were not signficantly different between the PMT vs CDT groups (7% vs 17%, p = 0.323). Limb salvage rate for PMT in this study was 93%, which was comparable to literature. Ansel et al. reported limb salvage rate of 89% at 1 month following PMT (Ansel et al., 2008).

This study is limited by its retrospective nature and unequal patient numbers between the PMT group and CDT group. However, there is a lack of randomized trials comparing these two treatments and the indications for these treatments in acute limb ischemia are not clear. The difference in costs between CDT and PMT were not evaluated, which may play a role in decision making because the clinical success rates are similar.

PMT is safe and effective as a primary treatment for ALI with a similar clinical outcome compared to CDT. Several treatment options are available for this patient group and the choice of treatment should still be on a case-by-case basis. Patients requiring quick revascularization (for example Rutherford IIB) and with contraindications for thrombolysis may benefit from PMT. Similarly, CDT can be the treatment of choice in patients with complex crural disease. A combination of these techniques should be considered when appropriate.