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apparent stroke had their care withdrawn before undergoing neuroimaging.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.