Clinical Imaging Factors Associated With Infarct Progression in Patients With Ischemic Stroke During Transfer for Mechanical Thrombectomy

Abstract

Importance: When transferred from a referring hospital (RH) to a thrombectomy-capable stroke center (TCSC), patients with initially favorable imaging profiles (Alberta Stroke Program Early CT Score [ASPECTS] ≥6) often demonstrate infarct progression significant enough to make them ineligible for mechanical thrombectomy at arrival. In rapidly evolving stroke care networks, the question of the need for vascular imaging at the RHs remains unsolved, resulting in an important amount of futile transfers for thrombectomy.

Objective: To examine the clinical imaging factors associated with unfavorable imaging profile evolution for thrombectomy in patients with ischemic stroke initially transferred to non-TCSCs.

Design, setting, and participants: Data from patients transferred from 1 of 30 RHs in our regional stroke network and presenting at our TCSC from January 1, 2010, to January 1, 2016, were retrospectively analyzed. Consecutive patients with acute ischemic stroke initially admitted to a non-thrombectomy-capable RH and transferred to our center for which a RH computed tomography (CT) and a CT angiography (CTA) at arrival were available for review.

Main outcomes and measures: ASPECTS were evaluated. The adequacy of leptomeningeal collateral blood flow was rated as no or poor, decreased, adequate, or augmented per the adapted Maas scale. The main outcome was an ASPECTS decay, defined as an initial ASPECTS of 6 or higher worsening between RH and TCSC CTs to a score of less than 6 (making the patient less likely to derive clinical benefit from thrombectomy at arrival).

Results: A total of 316 patients were included in the analysis (mean [SD] age, 70.3 [14.2] years; 137 [43.4%] female). In multivariable models, higher National Institutes of Health Stroke Score, lower baseline ASPECTSs, and no or poor collateral blood vessel status were associated with ASPECTS decay, with collateral blood vessel status demonstrating the highest adjusted odds ratio of 5.14 (95% CI, 2.20-12.70; P < .001). Similar results were found after stratification by vessel occlusion level.

Conclusions and relevance: In patients with ischemic stroke transferred for thrombectomy, poor collateral blood flow and stroke clinical severity are the main determinants of ASPECTS decay. Our findings suggest that in certain subgroups vascular imaging, including collateral assessment, can play a crucial role in determining the benefits of transfer for thrombectomy.

Figure.. Collateral Grading System

Collateral status was defined as follows: 1, absent collateral blood flow or less than 50% of the middle cerebral artery territory (no or poor); 2, collateral blood flow less than that on the contralateral side but more than 50% of the middle cerebral artery territory (moderate); 3, collateral blood flow equal to that of the contralateral side (adequate); and 4, collateral blood flow greater than that on the contralateral side (augmented).