EFFECTS OF VOLUME AND PRESSURE OVERLOADS AND MYOCARDIAL HYPERTROPHY ON EXERCISE-INDUCED CHANGES IN ELECTROCARDIOGRAPHIC QRS AMPLITUDE

To investigate the effects of volume and pressure overloads and myocar dial hypertrophy on exercise-induced changes in QRS amplitude, we revi ewed treadmill exercise electrocardiograms. In 10 normal young men, R( v5) amplitude decreased and S(v1) amplitude increased at peak exercise , and returned to the resting value in the recovery period. In 10 pati ents with aortic regurgitation, R(v5) and S(v1) amplitudes increased a fter 5 min of recovery. In 12 patients with essential hypertension and 10 with idiopathic hypertrophic non-obstructive cardiomyopathy, R(v5) amplitude remained unchanged or higher at peak exercise compared with the resting value, but patterns of serial changes were similar to tha t of normal subjects. In 9 patients with atrial septal defect, R'v1 am plitude increased with exercise, whereas it remained unchanged in 12 w ith isolated complete right bundle branch block. In 5 patients with mi tral stenosis, S(v1) amplitude decreased at peak exercise. In conclusi on, changes in QRS amplitude with exercise are influenced by hemodynam ic abnormality and myocardial hypertrophy, and a major determinant of these serial changes seems to be the change in ventricular volume.