Allometric scaling for left ventricular mass and geometry in male and female athletes of mixed and endurance sports.

Background: The athlete's heart (AH) defines the phenotypical changes that occur in response to chronic exercise training. Echocardiographic assessment of the AH is used to calculate LV mass (LVM) and determine chamber geometry. This is, however, interpreted using standard linear (ratiometric) scaling to body surface area (BSA) whereas allometric scaling is now widely recommended. This study (1) determined whether ratiometric scaling of LVM to BSA (LVMi^ratio) provides a size-independent index in young and veteran athletes of mixed and endurance sports (MES), and (2) calculated size-independent beta exponents for allometrically derived (LVMi^allo) to BSA and (3) describes the physiological range of LVMi^allo and the classifications of LV geometry.

Methods: 1373 MES athletes consisting of young (< 35 years old) (males n = 699 and females n = 127) and veteran (> 35 years old) (males n = 327 and females n = 220) were included in the study. LVMi^ratio was calculated as per standard scaling and sex-specific LVMi^allo were derived from the population. Cut-offs were defined and geometry was classified according to the new exponents and relative wall thickness.

Results: LVMi^ratio did not produce a size independent index. When tested across the age range the following indexes LVMi/BSA^0.7663 and LVMi/BSA^0.52, for males and females respectively, were size independent (r = 0.012; P = 0.7 and r = 0.003; P = 0.920). Physiological cut-offs for LVMi^allo were 135 g/(m²)^0.7663 in male athletes and 121 g/(m²)^0.52 in female athletes. Concentric remodelling / hypertrophy was present in 3% and 0% of young male and female athletes and 24% and 17% of veteran male and female athletes, respectively. Eccentric hypertrophy was observed in 8% and 6% of young male and female athletes and 9% and 11% of veteran male and female athletes, respectively.

Conclusion: In a large cohort of young and veteran male and female MES athletes, LVMi^ratio to BSA is not size independent. Sex-specific LVMi^allo to BSA with LVMi/BSA^0.77 and LVMi/BSA^0.52 for male and female athletes respectively can be applied across the age-range. Population-based cut-offs of LVMi^allo provided a physiological range demonstrating a predominance for normal geometry in all athlete groups with a greater percentage of concentric remodelling/hypertrophy occurring in veteran male and female athletes.