Thomas G. Devlin

Background and Purpose: The degree to which the coronavirus disease 2019 (COVID-19) pandemic has affected systems of care, in particular, those for time-sensitive conditions such as stroke, remains poorly quantified. We sought to evaluate the impact of COVID-19 in the overall screening for acute stroke utilizing a commercial clinical artificial intelligence platform. Methods: Data were derived from the Viz Platform, an artificial intelligence application designed to optimize the workflow of patients with acute stroke. Neuroimaging data on suspected patients with stroke across 97 hospitals in 20 US states were collected in real time and retrospectively analyzed with the number of patients undergoing imaging screening serving as a surrogate for the amount of stroke care. The main outcome measures were the number of computed tomography (CT) angiography, CT perfusion, large vessel occlusions (defined according to the automated software detection), and severe strokes on CT perfusion (defined as those with hypoperfusion volumes >70 mL) normalized as number of patients per day per hospital. Data from the prepandemic (November 4, 2019 to February 29, 2020) and pandemic (March 1 to May 10, 2020) periods were compared at national and state levels. Correlations were made between the inter-period changes in imaging screening, stroke hospitalizations, and thrombectomy procedures using state-specific sampling. Results: A total of 23 223 patients were included. The incidence of large vessel occlusion on CT angiography and severe strokes on CT perfusion were 11.2% (n=2602) and 14.7% (n=1229/8328), respectively. There were significant declines in the overall number of CT angiographies (−22.8%; 1.39–1.07 patients/day per hospital, P P P P P =0.9) and comprehensive stroke center hospitalizations (18.8% versus 11.0%, P =0.4). Conclusions: A significant decline in stroke imaging screening has occurred during the COVID-19 pandemic. This analysis underscores the broader application of artificial intelligence neuroimaging platforms for the real-time monitoring of stroke systems of care.

The Merci Retrieval System^® was cleared for use in patients with stroke in August 2004. However, there are few published results of “real world experience” with the device. We captured single-center data on 25 consecutive patients with acute ischemic stroke treated with the Merci Retrieval System according to the MERCI trial except that we treated some patients with tandem proximal carotid and intracranial lesions with carotid angioplasty and stenting and some patients were treated within the 3-hour window. Median patient age was 63 years and median initial National Institute of Health Stroke Scale (NIHSS) score was 18. Isolated M₁ or M₂ middle cerebral artery lesions occurred in 52% “carotid T” lesions in 8%, and vertebrobasilar lesions in 8% Tandem lesions involving proximal carotid and proximal intracranial vessel occurred in 32%, necessitating emergent multilevel treatment including carotid stenting. Median duration from symptom onset to Merci device utilization was 5.2 hours. Successful reperfusion (≥thrombolysis in myocardial infarction [TIMI] 2 flow) in the target vessel was obtained in 56% of cases. Statistical analysis revealed a strong correlation between ability to achieve greater than or equal to TIMI 2 flow a good clinical outcome as measured by 3-month NIHSS score, modified Rankin Scale (mRS), and mortality (nine out of the 12 without successful reperfusion died compared to none of the 13 with ≥TIMI 2 flow, p<0.001). Younger age and lower NIHSS score on presentation were also predictors of good clinical outcome at 3 months. These “real world data” demonstrate that the results of the previous MERCI trial can be “independently replicated” at a regional stroke center. Although the results of placebo-controlled trials are still pending, mechanical revascularization has become a critical component of our acute stroke protocol, particularly for severe strokes. Issues still remain regarding recalcitrant lesions and operator experience, which necessitate further clinical testing and device optimization.