Wayneho Kam, MD
Early mechanical thrombectomy (MT) with successful recanalization leads to better outcomes following acute ischemic stroke. However, reocclusion of the treated vessel can occur in certain patients. It is important to identify those patients who are at high risk for such events so that measures can be taken to prevent potential neurological deterioration.
The study by Marto et al. published in Stroke in August 2019 sought to address this very topic. The authors examined data from the Acute Stroke Registry and Analysis of Lausanne cohort and included patients with anterior and posterior circulation strokes who were treated with MT, with resultant TICI 2B-3, and had 24-hour vascular imaging available. Reocclusion was defined as a new intracranial occlusion within an arterial segment that was recanalized at the end of MT.
The authors of the study noted that of the 423 patients who met inclusion criteria, 28 (6.6%) had 24-hour reocclusion. A multivariate logistic regression analysis was conducted to investigate associated factors and 3-month outcome. They found that intracranial internal carotid artery occlusion (aOR, 3.53; 95% CI, 1.50-8.32), number of passes (aOR, 1.31; 95% CI, 1.06-1.62), transient reocclusion during MT (aOR, 8.55; 95% CI, 2.14-34.09), and atherosclerotic cause (aOR, 3.14; 95% CI, 1.34-7.37) were independently associated with reocclusion. Preadmission statin therapy (aOR, 0.27; 95% CI, 0.08-0.94) had a negative association and may be protective. A subsequent matched-cohort analysis showed that residual thrombus or stenosis on post-recanalization angiographic images was also associated with reocclusion (aOR, 15.6; 95% CI, 4.6-52.8). Furthermore, patients who had a 24-hour reocclusion were more likely to have unfavorable outcomes, with early neurological deterioration and worse 3-month prognosis as measured by modified Rankin Scale.
There were several limitations to this study, some of which were appropriately raised by the authors of the paper. The retrospective nature of the study and small number of patients do limit the interpretation of the results. Moreover, the study included patients over a large time period (2003 to 2018), where treatment criteria and techniques have substantially evolved. Patients who underwent thrombectomy in 2018 are not only different than those treated in 2003, but would inherently experience different outcomes. Indeed, mere differences in technique (greater time of onset-to-recanalization, greater time of groin puncture-to-recanalization, use of balloon angioplasty or stenting) were also found to be associated with reocclusion in this study.
In looking through the supplemental material further, it appears that standard protocol was to repeat vessel imaging 24 hours post-procedure for all patients, not just patients with clinical suspicion for reocclusion, thus eliminating this potential bias. Nevertheless, those who never got the necessary follow-up imaging may be vastly different than those who did; notably, data from the supplemental material suggests that a higher proportion of patients excluded from the study were female, had higher pre-stroke morbidity, were more likely to be diabetic, had parenchymal hematoma, had symptomatic hemorrhagic transformation, and had an unfavorable 3-month outcome. The exclusion of these patients could introduce unintended bias.
Findings from this study serve as a reminder that we should be mindful of certain factors that may predispose patients to reocclusion following successful MT. In addition to the above conclusions, it appears that younger age is also associated with reocclusion, perhaps suggestive of an undiagnosed hypercoagulable state as another causative mechanism. Future research should include trials that randomize patients to varying peri-procedure antithrombotic regimens, as well as timing of administration, and assess whether this would influence reocclusion rates.
