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Abstract
Background Atrial fibrillation is the most commonly encountered cardiac arrhythmia and an independent risk factor for cardioembolic (CE) stroke, conferring a 5-fold higher risk amongst affected individuals. Despite substantial progress in recognition and acute therapy, ischemic stroke remains a leading cause of disability and death worldwide. CE stroke, which accounts for 1 in 5 strokes, is associated with higher mortality rates, greater disability, greater recurrence rate and higher treatment costs when compared to patients with stroke from other causes. Despite its importance, the pathogenesis of atrial fibrillation is poorly understood, and the factors which contribute to the infarct burden in stroke is unclear.
Aim Evaluate the demographics of patients presenting with ischemic stroke to a national centre of excellence Identify echocardiographic/electrocardiographic factors influencing the infarct size in acute stroke.
Methods Retrospective cohort analysis was done on patients presenting to presented to Beaumont Hospital, between the months of January and July 2016 with an ischemic stroke. Left atrial volume, stroke volume on CT-Brain and Holter records were individually analysed by 3 independent physicians. Left atrial volume was measured using trans-thoracic echocardiogram in apical 4 chamber view using the length-area method at ventricular end systole while CVA infarct volume was assessed using similar length-area method on CT-Brain. SPSS was then used for statistical analysis.
Results 125 patients presented with acute ischemic stroke during the study period, with an average age of 69 years. 12 patients has significant carotid artery disease and were excluded from the study. Of the remaining 113 patients, 101 had an echocardiogram performed, 98 had holter monitoring performed (figure 1). The presence of atrial fibrillation was associated with a significantly larger left atrial diameter 4.5 cm vs 3.86 cm (p=0.000595), but identification of atrial fibrillation did not influence the volume of cerebral infarct (p=0.4084). In cases where the LA diameter >4.5 cm, and when controlling for the presence of atrial fibrillation, there was a significant increase in the cerebral infarct volume (43.89 ml vs 26.26 ml, p=0.039). Further multivariate analysis highlighted that the percentage of premature atrial complexes correlated poorly with both the presence of atrial fibrillation and also with infarct size in acute stroke (Pearson R, 0.0652, p=0.589). In those undergoing TOE, atrial fibrillation was associated with lower left atrial appendage exit velocities (24 cm/s vs 57 cm/s, p=0.0037), but the ejection velocities alone correlated poorly with infarct size (Pearson R, 0.3357, p=0.781).
Procedures performed
Conclusion The complex pathogenicity of atrial fibrillation, particularly in the most clinically relevant outcome i.e. acute stroke, is poorly understood. Interim results of this study showed that left atrial diameter >4.5 cm was associated with larger ischemic stroke volume independent of presence of atrial fibrillation and poor LAA velocity. This data suggests that the factors affecting the left atrium (separate from the left atrial appendage) have a role in the size of the cardioembolism, potentially contributing to infarct size.