The Influence of Left Atrial Enlargement on the Relationship between Atrial Fibrillation and Stroke

BackgroundLeft atrial enlargement (LAE) is independently associated with an increased risk of stroke and atrial fibrillation (AF). The combination of both LAE and AF possibly increases the risk of stroke beyond that observed with AF.MethodsThis analysis included 4572 (43% men, 95% white) participants from the Cardiovascular Health Study. LAE was defined using transthoracic echocardiographic 2-dimensional M-mode measurements of the left atrial diameter using sex-specific cut-points (men: ≥4.1 cm, women: ≥3.9 cm). AF cases were identified during the initial study electrocardiogram or by self-reported history. We examined the association between baseline AF and incident ischemic stroke stratified by the presence of LAE. Incident cases of ischemic stroke were identified by adjudication of medical records, including hospitalization data, through December 31, 2010.ResultsAt baseline, a total of 253 (5.5%) participants had AF and 1947 (43%) had LAE. Participants with AF (n = 163, 64%) were more likely to have LAE than those without AF (n = 1784, 41%; P < .001). Over a median follow-up of 13 years, 739 (16%) ischemic stroke events were identified. Both AF (hazard ratio [HR] = 2.12, 95% confidence interval [CI] = 1.64-2.74) and left atrial diameter (per 1-cm increase: HR = 1.14, 95% CI = 1.01-1.28) were associated with an increased risk for ischemic stroke. The association between AF and ischemic stroke was not modified by the presence of LAE (LAE: HR = 2.13, 95% CI = 1.42-3.19; no LAE: HR = 1.91, 95% CI = 1.36-2.68; P interaction = .86).ConclusionOur results suggest that echocardiographic LAE does not modify the stroke risk observed with AF.