Impact and pitfalls of scaling of left ventricular and atrial structure in population-based studies

Background: Several allometric methods for indexing cardiac structures to body size have been proposed but the optimal way for normalization of cardiac structures is still controversial. We aimed to estimate the allometric exponents that best describe the relationships between cardiac dimensions and body size, propose normative values, and analyze how the different scaling metrics influence the prevalence of left ventricular hypertrophy (LVH) and chambers enlargement as well as predictive models for cardiovascular outcome in the community. Methods: We measured left ventricular end-diastolic dimension, end-diastolic volume, left ventricular mass, and left atrial volume in randomly recruited population cohorts (n = 1509; 52.8% women; mean age, 47.8 years). Results: In a healthy subgroup (n = 656), the allometric exponents that described the relationships between left ventricular end-diastolic dimension and body size were 1, 0.5, and 0.33 for body height, body surface area (BSA), and estimated lean body mass, respectively. With regard to left ventricular end-diastolic volume, left ventricular mass, and left atrial volume the allometric exponents for body height were 2.9, 2.7, and 2.0, respectively; for BSA, they ranged from 1.7 to 1.8; for estimated lean body mass all exponents were around 1. These exponents were used to appropriately scale the cardiac dimensions to body size and derived sex-specific cut-off limits for different indexed cardiac dimensions. The hazard ratios of cardiovascular outcome were highest for LVH defined by left ventricular mass/height2.7. Conclusion: Our study resulted in a proposal for thresholds for various indexed cardiac dimensions. Left ventricular mass indexed to height was sensitive in detection of LVH associated with obesity and slightly better predicted outcome.