Electrocardiographic Left Atrial Abnormality and Risk of Stroke: Northern Manhattan Study

Embolic strokes of undetermined source comprise a subset of cryptogenic ischemic strokes. It is thought that some embolic strokes of undetermined source could be due to left atrial thromboembolism without atrial fibrillation. The authors sought to determine whether a marker of left atrial pathological changes could pose as a surrogate marker of nonarrhythmogenic atrial thromboembolism in embolic strokes of undetermined source. To this end, Kamel et al studied the association between electrocardiographic P-wave terminal force in lead V1 (PTFV1), which has been associated with ischemic stroke in the absence of atrial fibrillation, and cryptogenic ischemic strokes in the Northern Manhattan Study population. The authors designed a case–cohort study, randomly choosing a subcohort of participants who had electrocardiography (n=798), and all subjects who developed ischemic strokes in follow-up (n=241). Participants with atrial fibrillation at baseline or during follow-up were excluded. The study showed that in adjusted models, there was an association between PTFV1 and a composite of cryptogenic or cardioembolic stroke (adjusted hazard ratio per SD, 1.31; 95% confidence interval, 1.08–1.58). For cardioembolic or cryptogenic stroke, PTFV1 was associated with a 50% increase in risk (hazard ratio 1.56; 95% confidence interval, 1.25– 1.96). Interestingly, the associations between electrocardiographic left atrial abnormality and most stroke subtypes were attenuated after adjustment for left atrial size on echocardiogram, suggesting that PTFV1 may, in part, reflect left atrial dilatation. This interesting study, therefore, indicates that the strong association of PTFV1 with cardioembolic and cryptogenic strokes supports a specific link with left atrial thromboembolism, in the absence of atrial fibrillation. PTFV1 had good interand intrarater reliability in this study. Therefore, PTFV1 may be considered as a potential surrogate marker for atrial thromboembolism and, therefore possibly modifying therapeutic strategies in patients with embolic strokes of undetermined source at high risk for recurrent thromboembolism. See p 3208.