Racial Differences in Left Atrial Size: Results from the Coronary Artery Risk Development in Young Adults (CARDIA) Study.

Thomas A Dewland,Kofo O Ogunyankin,Donglei Hu,Kirsten Bibbins-Domingo,Elyse Foster,Joao A Lima,Feng Lin,Gregory M Marcus,Esteban G Burchard,Eric Vittinghoff,David R Jacobs,Tesfaye B Mersha

doi:10.1371/journal.pone.0151559

Abstract

Whites have an increased risk of atrial fibrillation (AF) compared to Blacks. The mechanism underlying this association is unknown. Left atrial (LA) size is an important AF risk factor, and studies in older adults suggest Whites have larger LA diameters. However, because AF itself causes LA dilation, LA size differences may be due to greater subclinical AF among older Whites. We therefore assessed for racial differences in LA size among young adults at low AF risk. The Coronary Artery Risk Development in Young Adults (CARDIA) study enrolled White and Black participants between 18 and 30 years of age. LA diameter was measured in a subset of participants using echocardiography at Year 5 (n = 4,201) and Year 25 (n = 3,373) of follow up. LA volume was also assessed at Year 5 (n = 2,489). Multivariate linear regression models were used to determine the adjusted association between race and LA size. In unadjusted analyses, mean LA diameter was significantly larger among Blacks compared to Whites both at Year 5 (35.5 ± 4.8 mm versus 35.1 ± 4.5 mm, p = 0.01) and Year 25 (37.4 ± 5.1 mm versus 36.8 ± 4.9 mm, p = 0.002). After adjusting for demographics, comorbidities, and echocardiographic parameters, Whites demonstrated an increased LA diameter (0.7 mm larger at Year 5, 95% CI 0.3–1.1, p<0.001; 0.6 mm larger at Year 25, 95% CI 0.3–1.0, p<0.001). There was no significant association between race and adjusted Year 5 LA volume. In conclusion, in a young, well-characterized cohort, the larger adjusted LA diameter among White participants suggests inherent differences in atrial structure may partially explain the higher risk of AF in Whites. The incongruent associations between race, LA diameter, and LA volume suggest that LA geometry, rather than size alone, may have implications for AF risk.

Highlights

Atrial fibrillation (AF) is the most commonly encountered clinical arrhythmia, the factors responsible for its induction and perpetuation remain incompletely understood [1]
Previous studies have found that Whites may have significantly larger left atrial (LA) diameters compared to Blacks [8,9], raising the possibility that the race-atrial fibrillation (AF) association could be mediated by inherent racial differences in atrial size
After controlling for several demographic variables and clinical comorbidities, adjusted LA diameter was significantly greater among Whites

Summary

Introduction

Atrial fibrillation (AF) is the most commonly encountered clinical arrhythmia, the factors responsible for its induction and perpetuation remain incompletely understood [1]. Compared to Whites, Blacks have more established AF risk factors yet paradoxically exhibit a 25–40% reduced risk of the disease [2,3]. Both White race and European ancestry are independently associated with AF risk [2,3,4]. Previous studies have found that Whites may have significantly larger LA diameters compared to Blacks [8,9], raising the possibility that the race-AF association could be mediated by inherent racial differences in atrial size. Since AF itself may cause LA enlargement [10,11,12], it remains unclear whether these observed differences in atrial size by race are instead an artifact of a greater subclinical AF burden among older Whites compared to Blacks

Methods

Results

Conclusion