Muhammad Zeeshan Memon, MD
Currently, the American Heart Association/American Stroke Association recommends mechanical thrombectomy as the standard of care for acute stroke patients with proximal artery occlusions. Multiple studies have shown complete or near-complete reperfusion achieved in a timely manner leads to improved clinical outcomes and reduced adverse effects; however, complete reperfusion is achieved in <50% of cases, and often requires many thrombectomy attempts and the use of multiple devices. This not only delays time to achieve recanalization, but also incurs additional risk of vessel spasm, injury, and rupture. Design improvement of mechanical thrombectomy devices, particularly the advent of stent retrievers, has improved recanalization rates and decreased the complication rates leading to this notion that achieving complete revascularization with a single pass should be the new angiographic goal.
In the March 2018 issue of Stroke, Zaidat et al introduced and evaluated a new metric for thrombectomy devices, the first pass effect (FPE). They studied FPE with the Solitaire FR device within a large cohort of patients from the North American Solitaire Acute Stroke (NASA) Registry database from March 2012 to February 2013 at 24 North American medical centers. They defined FPE as: (1) single pass/use of the device; (2) complete revascularization of the large vessel occlusion and its downstream territory (Modified Thrombolysis in Cerebral Infarction [mTICI] 3); and (3) no use of rescue therapy. They reported clinical and angiographic outcomes of patients between FPE and non-FPE populations.
Three hundred fifty-four patients were included in the NASA registry, out of which 25.1% achieved FPE. The study demonstrated that the FPE patients had significantly better 90-day clinical outcomes than those in the non-FPE population (mRS score <=2 61.3% versus 35.3%; P=0.01; odds ratio, 1.7; 95% confidence interval, 1.1–2.7). 90-day mortality rate (16%) and symptomatic intracranial hemorrhage rate (5.6%) was significantly lower in the FPE group compared with the non-FPE cohort. Predictors of achieving FPE were the use of balloon guided catheters, whereas the ICA terminus occlusion predicted failure to achieve FPE.
Despite these interesting findings, this study had several limitations. First, the study was not designed to study FPE rather report an observation from their registry. Secondly, the study had a small number of patients treated with the combined aspiration and stent retriever thrombectomy or aspiration-first approach, making it hard to distinguish the effect of this combination approach vs. FPE only. The authors hinted at the potential benefit of the aspiration-first approach in achieving rapid and high rate of FPE from a single attempt, but left it to future studies to address this. Nevertheless, Dr. Zaidat’s study findings reiterate the importance of early and complete reperfusion in acute ischemic stroke patients and establish FPE as a potential benchmark to measure the angiographic efficacy and a possible surrogate for clinical efficacy for emerging thrombectomy devices.