Cardiac refractoriness. Age-dependence in normal subjects.

The effects of age on cardiac electrophysiologic measurements were assessed in 30 subjects between the ages of 18 and 73 years and free of structural heart disease. Occult heart disease was excluded by a normal treadmill exercise tolerance test, a rest and exercise radionuclide angiogram, and/or a cardiac catheterization. Effective and functional refractory periods of right atrium, right ventricle, and atrioventricular node were assessed. The relationship between these measurements and age was examined using linear regression. There were significant correlations between age and atrial effective and functional refractory periods, atrioventricular effective refractory period, and ventricular effective and functional refractory periods. Other electrophysiologic measures showed no such relationship with age.