Associations of Electromechanical Activation Time With Cardiac Structure and Function and Clinical Outcomes

The electromechanical activation time (EMAT) measured by acoustic cardiography is the time between QRS onset and the first heart sound. Increased EMAT is associated with a reduced left ventricular ejection fraction (LVEF).

The objective of the study was to determine whether EMAT has utility as a cardiovascular (CV) screening test in the community.

Participants (n = 3,401) in Dallas Heart Study-2 had acoustic cardiography, cardiac magnetic resonance imaging, and blood sampling at baseline. Clinical outcomes, including a composite of CV death/heart failure (HF) hospitalization or major adverse clinical events (CV death, HF hospitalization, nonfatal myocardial infarction, stroke, and atrial fibrillation), were ascertained after a median follow-up of 12.4 years. Multivariable models evaluated whether EMAT was associated with cardiac structure and function and clinical outcomes. Discrimination for reduced LVEF (<55%) was assessed by C-statistics.

Higher continuous EMAT was independently associated with a lower LVEF (P < 0.001) and greater left ventricular end-diastolic volume (P = 0.04). However, an increased EMAT had poor discrimination for reduced LVEF (C-statistic = 0.52), was inferior to N-terminal pro-B-type natriuretic peptide (NT-proBNP) (C = 0.59, P < 0.01 vs EMAT), and did not improve discrimination beyond NT-proBNP alone (P = 0.90). Baseline EMAT was associated with CV death/HF hospitalization (HR: 1.3; 95% CI: 1.2-1.4; P < 0.001) and with major adverse clinical events (HR: 1.2; 95% CI: 1.1-1.4; P < 0.001) in models adjusted for age, race, and sex, but these associations did not persist after additional adjustment for NT-proBNP (P > 0.10 for both).

In a community cohort, an increased EMAT was associated with a lower LVEF and adverse prognosis but had poor discriminatory capacity for the former and was not independent of NT-proBNP for the latter.