Abstract 2564: The Reported Association Between Coronary Artery Calcium and QTc Interval is Explained by Differences in Left Ventricular Mass: From the Dallas Heart Study
Introduction. Although the relation between ventricular arrhythmia and myocardial ischemia from advanced coronary atherosclerosis is well-established, only a single study has linked subclinical atherosclerosis with abnormal ventricular repolarization.
Methods. Assessment of cardiac structure and function by MRI, measurement of CAC by EBCT, and 12-lead ECGs were performed in 2438 subjects from the Dallas Heart Study (48% African-American, 55% female), a multi-ethnic population-based sample of Dallas residents ages 30 – 65. The relation between QTc interval and CAC was evaluated both before and after adjustment for potential confounders including LV mass. All analyses were stratified by sex.
Results. In unadjusted models, CAC positively associated with QTc interval in both sexes (Table⇓). In an analysis replicating the sole prior published study (Model 1) this relation remained significant among men, but not women. With further adjusting for LV mass (Model 2), the overall explanatory power of the models increased, but the association between CAC and QTc was no longer significant in either sex. LV mass remained highly associated with QTc in adjusted analyses (p=0.0001).
Conclusion. In a large multi-ethnic population-based cohort with detailed cardiac phenotyping, we show that subclinical coronary atherosclerosis is not associated with QTc after accounting for LV mass. These findings suggest that associations between subclinical atherosclerosis and repolarization may be mediated through common associations with increased LV mass, an important independent determinant of QTc, rather than by direct effects of subclinical atherosclerosis on the myocardium.