W: Relationship of QRS amplitude changes during exercise to left ventricular function and volumes and the diagnosis of coronary artery disease. Circulation 60: 1004

SUMMARY Preliminary studies have suggested that QRS-amplitude changes due to exercise-induced alterations in ventricular volume and function can improve the diagnostic value of the exercise test. To evaluate this, electrocardiographic data and equilibrium radionuclide angiographic images were recorded simul-taneously in 18 normal subjects and 60 coronary artery disease patients at rest and during supine bicycle exer-cise. In 24 of the 60 coronary artery disease patients, left ventricular volumes were also calculated. The measured QRS amplitudes were the R waves in V, X, Y and Z, the Q wave in Z and the sum of amplitudes of R waves in X and Y and the Q wave in Z (2iR). The mean left ventricular ejection fraction increased signifi-cantly from rest to peak exercise in the normal subjects; however, the mean left ventricular ejection fraction and mean volumes did not change significantly in the coronary patients. There was no significant difference in the mean QRS-amplitude changes during exercise between the coronary artery disease patients and the normal subjects in any of the measured leads. The sensitivity and specificity of exercise-induced QRS-amplitude changes for coronary disease were lower than ST-segment changes. For ST-segment changes, the sensitivity was 57 % and specificity was 100%; the best sensitivity and specificity for QRS amplitude occurred in RZ, 48% and 67%, respectively. When ejection fraction was related to 2R at rest and peak exercise for both normal sub-jects and coronary patients the correlations were fair (0.50, 0.51 respectively); however, the correlatio