Q. What is R - Wave Amplitude?
The R-wave amplitude in the lateral precordial leads usually decreases more in normal than in abnormal subjects and correlates with left ventricular function. Patients with CAD (severe) are likely to have an increase in the R-wave amplitude with exercise. As exercise progresses and the heart rate increases, R-wave amplitude increases normally until the heart rate is approximately 120 or 130 beats per minute, and then the amplitude begins to decrease. This suggests that for the R-wave to have significance, an increase in amplitude should be at a heart rate greater than 120 bpm. The sensitivity of an R-wave increase is rather poor but the specificity can be good if the patient reaches high heart rates. Stress test responses are difficult to analyze in patients with LBBB. Lee and colleagues reported that R-wave changes in 23 patients with LBBB had a 93 per cent sensitivity, 88 per cent specificity and 93 per cent predictability. A reduction in amplitude helps to predict normal coronary arteries and good left ventricular function in LBBB. Berman and associates used the sum of the R-waves in aVL, aVF and V3 and V4, plus S and V1 and V2 and were able to identify CAD in 93 per cent of 230 patients subsequently studied with coronary angiography. An R-wave increase is reported with vasospastic angina and early in the course of a myocardial infarction, where it is predictive of the severity and the likelihood of severe arrhythmias.