Abstract 12311: Increased Repolarization Lability Predicts Sudden Cardiac Death in Asymptomatic Adults

Abstract

Introduction. The overwhelming majority of sudden cardiac deaths (SCDs) occur in asymptomatic adults. Improved strategies are needed to identify those at high risk. Increased repolarization lability characterizes a substrate of life-threatening ventricular arrhythmia. We hypothesized that increased repolarization lability will be an independent predictor of SCD in asymptomatic adults.

Method. We analyzed baseline resting digital 12-lead ECGs of 15574 participants of the prospective community-dwelling Atherosclerosis Risk In Communities (ARIC) cohort. After exclusion of poor quality ECGs and individuals not in sinus rhythm at baseline, 15300 ECGs were analyzed. The inverse Dower transformation was applied to construct orthogonal XYZ leads and vectorcardiograms. The spatial TT’ angle, reflecting repolarization lability, was calculated by custom Matlab software as the angle between two consecutive T vectors using the definition of the inner product.

Results. During a median follow-up of 17 years, 243 cases of SCD and 174 cases of non-sudden cardiac death occurred. Mean spatial TT’ angle was larger in persons with SCD (6.6±5.4 vs. 5.2±3.8 deg, P=0.0003). In univariate Cox regression, the hazard for persons with the highest quartile of mean TT’ angle was about 2 times that of those with the three lower quartiles of mean TT’ angle (hazard ratio (HR): 1.80; 95% CI 1.39-2.34; P<0.0001). Spatial TT’ angle remained a significant predictor of SCD (HR: 1.57; 95% CI 1.14-2.18; P=0.0063) even after adjusting for age, gender, race, history of myocardial infarction, hypertension, diabetes mellitus, smoking, total cholesterol, high density lipoprotein, level of physical activity, mean T wave amplitude on XYZ leads, spatial QRS-T angle, QTc, and mean spatial T vector magnitude. In multivariate competing risk analysis mean spatial TT’ angle was associated with SCD (subhazard ratio: 1.58; 95% CI 1.15-2.17; P=0.005), but not with non-sudden cardiac death (subhazard ratio: 1.17; 95% CI 0.81-1.69; P=0.399).

Conclusion. Increased repolarization lability as measured by the mean spatial TT’ angle on the routine resting 12 lead ECG is an independent predictor of SCD in community-dwelling cohort of asymptomatic adults.