Background: Clinical features that consistently predict ischemic stroke in patients with nonvalvular atrial fibrillation have been identified, while echocardiographic risk factors are less well defined.
Objective: To determine whether the results of transthoracic echocardiography add independent information to the clinical risk factors for stroke in patients with atrial fibrillation.
Methods: Transthoracic echocardiographic findings and clinical features from 1066 patients with atrial fibrillation assigned to placebo or control in 3 randomized trials (Boston Area Anticoagulation Trial for Atrial Fibrillation, Stroke Prevention in Atrial Fibrillation I Study, and Veterans Affairs Prevention in Atrial Fibrillation Study) were correlated with subsequent ischemic stroke by multivariate analysis.
Results: The mean + SD age of patients was 67 +/- 10 years, 78% were men, 55% had a history of hypertension, 19% had a history of diabetes, 7% had a previous transient ischemic attack or stroke, and 27% had a history of heart failure. During a mean follow-up of 1.6 years, 78 ischemic strokes occurred (annual rate, 4.7%). Moderate to severe left ventricular systolic dysfunction shown via 2-dimensional echocardiography was a strong independent predictor of stroke (relative risk, 2.5; P<.001) in the 1010 patients in whom echocardiographic values for left ventricular function were available. Left atrial diameter by M-mode echocardiography did not predict stroke (relative risk, 1.02/mm; P = .10). Of 163 patients categorized as low risk based on clinical features (annual stroke rate, 0.8%; 95% confidence interval, 0.2%-3.0%), 10 had moderate to severe left ventricular dysfunction shown via 2-dimensional echocardiography and a 9.3% per year risk of stroke (95% confidence interval, 1.3%-66%). Conversely, 728 of the 847 patients at high risk for stroke based on clinical criteria had normal or mildly abnormal left ventricular function; their stroke rate was 4.4% (95% confidence interval, 3.4%-5.8%).
Conclusions: Left ventricular systolic dysfunction shown via 2-dimensional transthoracic echocardiography independently predicts risk of stroke in patients with atrial fibrillation. Echocardiography may prove most useful in a small group of patients who have a low risk of stroke according to clinical factors.