Stroke definition, diagnosis, and classification
In line with the most recently updated definitions by the American Heart Association 11, ischemic stroke (IS) was defined as any focal neurological deficit either with an associated infarct noted on neuro-imaging or with clinical evidence of cerebral focal ischemic injury lasting at least 24 hours. Intracerebral hemorrhage (ICH) was defined as intra-parenchymal bleeding not related to trauma without evidence of significant adjacent hypodensity on computed tomography (CT) scan. Ischemic Stroke with hemorrhagic transformation (HT) was defined as intra-parenchymal bleeding with significant adjacent hypodensity on CT, consistent with hemorrhage into the bed of an infarct.
Patient sedation was turned off on a daily basis for neurological monitoring, and patients with suspected stroke were examined by a board-certified neurologist at our institution and underwent a full neurological examination. We defined strokes occurring within 7 days of ECMO decannulation as ECMO-related stroke because, in some cases, clinical neurological examinations were not feasible or reliable due to delirium or other causes and diagnosis of stroke could be delayed7. Anticoagulation was held until neurological evaluation was completed. Condition permitting, patients underwent neuro-imaging with non-contrast computed tomography (CT). Patients with negative findings on CT but with clinical suspicion of stroke underwent further neuroimaging, with two patients with confirmed stroke on computed tomography angiography, and one patient with confirmed stroke on magnetic resonance imaging. Stroke lesions were confirmed with neuro-imaging findings and classified as IS, HT or ICH and were subdivided into right hemispheric, left hemispheric, bilateral hemispheric, or vertebrobasilar lesions. One patient with clinically apparent stroke had their care withdrawn before undergoing neuroimaging. This patient, although classified as having a stroke event, was not included in the stroke subtype and location analysis due to the absence of neuroimaging. Ischemic stroke lesions that underwent hemorrhagic transformation were classified as one stroke event. In 3 patients, stroke became evident after ECMO decannulation. For patients who were decannulated from ECMO and had a stroke event after being transferred to a separate mechanical circulatory device, determining whether the stroke was related to ECMO or another device is difficult. As such, patients with stroke event occurring 7 days post-ECMO removal or occurring within 7 days post-ECMO removal while being supported on a separate mechanical circulatory device (except for an Impella device or intra-aortic balloon pump (“IABP”)) were classified as having no stroke event, as these stroke events were not considered to have occurred while on ECMO.