Integrated left ventricular mass and left atrial function for prediction of cardiovascular outcomes: the Multi-Ethnic Study of Atherosclerosis.

Left ventricular (LV) mass and left atrial (LA) strain are physiologically coupled and individually predict adverse cardiovascular outcomes. Their imbalance may reflect early atrioventricular uncoupling and atrial myopathy before overt structural disease. We evaluated whether a cardiac magnetic resonance (CMR)-derived LV mass-to-LA strain ratio identifies early atrioventricular mechanical uncoupling and predicts cardiovascular events. Participants from the Multi-Ethnic Study of Atherosclerosis underwent CMR at exams 1 (2000-2002) and 5 (2010-2012). The LV mass-to-LA strain ratio was calculated as indexed end-diastolic LV mass divided by peak LA strain. Classification and regression tree analysis identified cut points for baseline ratio and longitudinal change, defining low (<1.04), reference (1.04-3.26), and high (>3.26) groups, and lesser-(≤130%) versus greater-change (>130%) groups. Multivariable Cox models assessed associations with heart failure (HF), atrial fibrillation (AF), myocardial infarction (MI), and all-cause mortality. Among 4,232 participants (mean age 61.5 ± 10.1 yr; 52.8% female), the mean ratio was 1.95 ± 0.72. Over a median 18-yr follow-up, 6.0% developed HF, 5.2% MI, 18.7% AF, and 25.6% died. A high LV mass-to-LA strain ratio independently predicted HF [hazard ratio (HR) 2.85], AF (HR 2.00), MI (HR 1.96), and death (HR 1.70; all P ≤ 0.003). With repeat CMR, an increasing ratio also predicted cardiovascular events, including among individuals with normal LV mass and LA strain. Higher baseline ratios were associated with progression toward abnormal volumetric atrioventricular coupling over time. A higher LV mass-to-LA strain ratio and its increase independently predict cardiovascular events before overt chamber abnormalities, supporting impaired atrial adaptation as an early stage of atrial myopathy.NEW & NOTEWORTHY Left atrial failure underlies two of the most consequential conditions in cardiovascular medicine: atrial fibrillation, with predisposition to stroke and dementia, and heart failure with preserved ejection fraction, a leading cause of hospitalization and mortality. By examining the relationship between left ventricular hypertrophy and left atrial deformation at the population level, we demonstrate that the LV mass-to-LA strain ratio identifies a threshold beyond which adverse atrial remodeling independently predicts incident cardiovascular events-even within normal ranges.