Important physiologic mechanisms have been thought not to exhibit large amounts of variability, due in part to the assumption that critical biologic functions will have evolved to an evolutionary optimum. The attainment of this optimum would necessarily eliminate individual differences in these variables. Using a sample of monozygotic and dizygotic twins reared apart since birth or early infancy, 12-lead electrocardiographic recordings and vectorcardiograms were obtained. Values of these variables for monozygotic and dizygotic twins reared together were obtained from other studies. Maximum likelihood tests of genetic and environmental components of variation for PR interval, QRS duration, QT interval and ventricular rate indicated a significant contribution of genetic effects (most heritabilities ranged from 30 to 60%), with a negligible contribution from common familial environmental effects.
|Original language||English (US)|
|Number of pages||4|
|Journal||The American Journal of Cardiology|
|State||Published - Mar 1 1989|
Bibliographical noteFunding Information:
From the Departments of Medicine, Psychology, Psychiatry and Laboratory Medicine/Pathology, and the Institute of Human Genetics, University of Minnesota, Minneapolis, Minnesota. This study was supported in part by grants from the Pioneer Fund, New York, New York, the Seaver Institute, Los Angeles, California, the Koch Charitable Foundation, New York, the Spencer Foundation, Chicago, Illinois, Harcourt Brace Jovanovich Inc., San Diego, California, and the Graduate School of the University of Minnesota and grant BNS 7926654 from the National Science Foundation. Manuscript received June 21, 1988; revised manuscript received and accepted November 28, 1988.