Left Atrial Mechanical Function and Incident Ischemic Cerebrovascular Events Independent of AF: Insights From the MESA Study

Objectives: This study sought to assess the association of baseline left atrial (LA) phasic function measured with cardia magnetic resonance (CMR) and incident ischemic cerebrovascular events (CVE). Background: LA remodeling is a known predictor of atrial fibrillation (AF), which is a risk factor for ischemic CVE. Despite studies showing an association between LA remodeling and ischemic CVE, the association of LA mechanical function with ischemic CVE in a population free of known cardiovascular disease is not fully studied. Methods: Phasic LA volumes; total, passive, and active LA emptying fractions (LAEF); and peak longitudinal LA strain were measured using feature-tracking CMR in 4,261 MESA (Multi-Ethnic Study of Atherosclerosis) participants (61 ± 10 years of age; 48% male). All individuals were free of clinical cardiovascular disease at baseline. Participants were followed for 11.6 ± 3.5 years for the diagnosis of incident ischemic CVE, defined as ischemic stroke or transient ischemic attack adjudicated by vascular neurologists. Results: During the follow-up, 193 (1.26 per 1,000 person-years) ischemic CVE (134 ischemic strokes and 59 TIAs) occurred. Individuals with incident ischemic CVE had larger LA volumes and lower passive, active, and total LAEFs at baseline. In multivariate analysis adjusted for known CVE risk factors, left ventricular mass and interim AF, total LAEF was associated with incident ischemic CVE (hazard ratio [HR]: 0.85 per SD; 95% confidence interval [CI]: 0.74 to 0.98; p = 0.027). The unadjusted HR for the lowest tertile of total LAEF compared to the highest tertile was 2.0 (95% CI: 1.43 to 2.79; p < 0.001), and the adjusted HR was 1.47 (95% CI: 1.04 to 2.05; p = 0.031). Addition of total LAEF to known clinical risk factors of CVE and left ventricular mass resulted in an improved predictive accuracy (C statistic of 0.76 vs. 0.73, respectively; p = 0.039). Conclusions: Reduced total LAEF was associated with incident ischemic CVE independent of known cerebrovascular risk factors and incident AF. Assessment of LA function may add further information in stratifying asymptomatic individuals at risk for ischemic stroke.

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