ELECTROCARDIOGRAM-R WAVE AMPLITUDE CHANGES DURING EXERCISE - RELATION TO LEFT-VENTRICULAR VOLUME CHANGES

Changes in electrocardiogram R wave amplitude often are noted during exercise in patients with coronary artery disease. The mechanism of this change in amplitude is unclear, though a relation to left ventricular volume changes has been suggested. To assess ischemia-independent relations between exercise R wave amplitude changes and volume we used radionuclide angiography and electrocardiogram at rest and exercise in 24 patients with chronic aortic regurgitation (without apparent coronary artery disease) as a sole cardiac abnormality. Of the 24 patients studied, the left ventricular end-diastolic volume increased in 14 (58%) and decreased in 10 (42%), and the left ventricular end-systolic volume increased in 13 (54%) and decreased in 11 (46%). The R wave amplitude increased in 4 (17%), decreased in 9 (37%), and was unchanged in 11 (46%). No significant differences existed among the frequency of directional change of left ventricular volume between the groups defined by direction of R wave amplitude change. No correlation existed between R wave amplitude changes (rest to exercise) and end-diastolic and end-systolic volume changes. We conclude that R wave amplitude changes during exercise are not explained by variations in the left ventricular volume.