Allometric Relationships for Cardiac Size and Longitudinal Function in Healthy Chinese Adults - Normal Ranges and Clinical Correlates.

BACKGROUND: Cardiac size measurements require indexing to body size. Allometric indexing has been investigated in Caucasian populations but a range of different values for the so-called allometric power exponent ( b ) have been proposed, with uncertainty as to whether allometry offers clinical utility above body surface area (BSA)-based indexing. We derived optimal values for b in normal echocardiograms and validated them externally in cardiac patients.

METHODS AND RESULTS: Values for b were derived in healthy adult Chinese males (n=1,541), with optimal b for left ventricular mass (LVM) of 1.66 (95% confidence interval 1.41-1.92). LV hypertrophy (LVH) defined as indexed LVM >75 g/m1.66 was associated with adverse outcomes in an external validation cohort (n=738) of patients with acute coronary syndrome (odds ratio for reinfarction: 2.4 (1.1-5.4)). In contrast, LVH defined by BSA-based indexing or allometry using exponent 2.7 exhibited no significant association with outcomes (P=NS for both). Cardiac longitudinal function also varied with body size: septal and RV free wall s', TAPSE and lateral e' all scaled allometrically ( b =0.3-0.9).

CONCLUSIONS: An optimal b of 1.66 for LVM in healthy Chinese was found to validate well, with superior clinical utility both to that of BSA-based indexing and to b =2.7. The effect of allometric indexing of cardiac function requires further study.