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.