Pathophysiological determinants of worse stroke outcome in atrial fibrillation

The reasons for worse outcome following ischemic stroke in patients with atrial fibrillation (AF) remain unclear. We aimed to elucidate the pathophysiological determinants of poorer stroke outcome in patients with AF using systematic MRI data from the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET).

Comparisons of infarct size, hypoperfusion volume, infarct growth, arterial occlusion, recanalization, reperfusion, hemorrhagic transformation and stroke severity were made between patients with and without AF enrolled in the EPITHET study.

AF was present in 42 of 101 patients. At baseline, AF patients were older (79 vs. 73 years, p = 0.02), had more severe neurological impairment (National Institutes of Health Stroke Scale score 16 vs. 11, p = 0.006), larger infarcts (29 vs. 15 ml, p = 0.04) and greater volumes of more severe hypoperfusion (T(max) > or =8 s, perfusion-weighted imaging volume 70 vs. 43 ml, p = 0.01) compared to patients without AF. There were no significant differences in arterial occlusion site, infarct growth, recanalization or reperfusion. At outcome, AF patients had larger infarcts (52 vs. 16 ml, p = 0.05), more severe hemorrhagic transformation (29 vs. 5%, p = 0.002 for parenchymal hematomas), greater disability (modified Rankin Scale score 4 vs. 3, p = 0.03) and higher mortality rates (31 vs. 12%, p = 0.04). AF was an independent predictor of parenchymal hematoma (OR = 6.90, 95% CI = 1.57-30.25), but not mortality (OR = 2.56, 95% CI = 0.83-7.85).

Patients with AF have worse clinical and imaging outcomes following ischemic stroke. This study suggests that the adverse effect of AF is due to greater volumes of more severely hypoperfused tissue, leading to larger infarct size and greater risk of severe hemorrhagic transformation.