Inheritance of acute cardiac changes during bicycle exercise: an echocardiographic study in twins.

Abstract

The inheritance of cardiac changes during acute dynamic physical exercise was studied in 21 pairs of monozygotic and 12 pairs of dizygotic male twins, ages 18-31 yr. Echocardiography was performed in resting conditions and at submaximal supine bicycle exercise at a heart rate of 110 bpm. In resting conditions significant heritability could be demonstrated for end-diastolic mean wall thickness, but not for left ventricular diameter and fractional shortening. Also for the change of mean wall thickness from rest to exercise, no significant heritability could be demonstrated. The increase of end-diastolic left ventricular internal dimension from rest to exercise showed a genetic component of 24% (P less than 0.05). Inheritance accounted for 47% (P less than 0.001) of the total phenotypic variance of the increase of fractional shortening from rest to exercise. In conclusion, the data suggest that the capacity of increasing end-diastolic left ventricular internal dimension and increasing fractional shortening during submaximal exercise has, unlike findings at rest, a significant genetic component.