[Is there a specific response of the ECG R-wave amplitude to exercise-induced myocardial ischemia? Exercise test and dipyridamole test]

Abstract

Changes in electrocardiogram R-wave amplitude are often noted during treadmill stress testing. The two main reasons for this phenomenon discussed in the literature are left ventricular dimension changes and myocardial ischemia. To evaluate the relation between myocardial ischemia and electrocardiogram R-wave amplitude changes, we investigated in a retrospective study the data of 99 patients (20 females/79 males) with clinical signs of coronary artery disease. All patients had undergone exercise ECG and dipyridamole test. Electrocardiogram R-wave amplitude changes and ST-segment alterations were measured before, during and after provocation by bicycle stress test and intravenous dipyridamole. In neither test was there a specific reaction of R-wave amplitude to myocardial ischemia. During myocardial ischemia there were patients with an increase as well as a decrease R-wave amplitude. There was no significant correlation between the reaction of the R-wave amplitude in the exercise ECG when compared with the Dipyridamole test. Quantitative analysis showed a reduction of R-wave amplitude during maximum provocation in both tests, which was statistically significant in almost every subgroup of patients. In both tests the ST-segment depression was statistically significant in all groups, but there was no significant correlation between the reaction of R-wave amplitude and the ST-segment depression. In conclusion, there is no specific reaction of R-wave amplitude to myocardial ischemia. It is very unlikely, that the often noted changes in R-wave amplitude during stress testing are caused by ischemic episodes of the myocardium. Other mechanisms must be sought to explain the observed R-wave alterations.