Introduction: When transferred from a referring hospital (RH) to a thrombectomy capable stroke center (TCSC), patients with initially favorable imaging profile (ASPECT score ≥6) often demonstrate infarct progression significant enough to make them ineligible at arrival. We sought to determine the clinical and imaging factors associated with this phenomenon in transferred ischemic stroke patients.
Methods: We identified adult stroke patients transferred from one of 30 RH between 2010 and 2016 for which (1) a RH computed tomography (CT) and (2) a CT Angiography (CTA) at arrival were available for review. ASPECT scores were evaluated by 2 raters. The adequacy of leptomeningeal collateral flow was rated as none/poor, decreased, adequate or augmented per the Maas et al (Stroke 2009), modified scale. ASPECTS decay was defined as an ASPECT initial score ≥6 worsening between RH and TCSC CTs to a score <6.
Results: A total of 330 patients were included in the analysis (mean age 70.2 ± 14.2, 43.3% females). Univariable subgroup analyses showed that patients with ASPECTs decay were more likely to be females (55% vs 40%, p=0.02), not on anticoagulants (4% vs 15%, p=0.01), and with higher initial NIHSS (Median [IQR] 19 [15.3-22] vs 11 [6-17], p<0.001), hyperdense vessel sign on initial CT (71% vs 26%, p<0.001) and poor collaterals on CTA (72% vs 19%, p<0.001). In multivariable models, higher NIHSS, lower baseline ASPECTs, CTA evidence of a proximal occlusion, and none/poor collaterals were strong predictors of ASPECTs decay, with collateral status demonstrating the highest odds ratio (aOR 10.3, 95%CI: [4.1-29], p<0.001). Similar results were found after stratification by vessel occlusion level.
Conclusion: In ischemic stroke patients transferred for thrombectomy, poor collateral flow, stroke severity and proximal vascular occlusion, but not time interval, are the main determinants of ASPECTs decay.