Electrocardiographic (ECG) abnormalities and coronary artery calcium (CAC) identify different aspects of subclinical coronary heart disease (CHD). We sought to determine whether ECG abnormalities improve risk prediction for all CHD and fatal CHD events jointly with CAC measures.

We included 6,406 men and women from the MESA aged 45 to 84 years who were free of cardiovascular disease at the time of enrollment (2000-2002). We stratified participants by presence of ST-T and Q wave abnormalities: any major, any minor/no major, and no major/minor using the Minnesota Code classifications. CAC score was defined into one of the following strata: 0, 1 to 100, 101 to 300, greater than 300. We created risk prediction models using MESA-specific coefficients for traditional risk factors (RFs) and calculated categorical net reclassification improvement (NRI) for all and fatal CHD.

Over a median follow-up of 10 years, we observed that the addition of ECG abnormalities to a risk prediction model for all CHD resulted in a categorical NRI of 0.05 (P = .04). For fatal CHD alone, the addition of ECG abnormalities resulted in categorical NRI of 0.09 (P = .02). Addition of ECG abnormalities to a model containing RFs and CAC resulted in categorical NRI of 0.02 (P = .11) for all CHD events. We also observed differences in the association between ECG abnormalities and CHD when stratifying by CAC presence.

Electrocardiographic abnormalities improved risk prediction for CHD when added to RFs but not when added to CAC. Electrocardiographic abnormalities particularly improved risk prediction for fatal CHD.