Electrocardiographic evidence of ischemia during ventricular paced rhythms

Exercise-induced electrocardiographic (ECG) changes are the most widely recognized noninvasive means for detecting myocardial ischemia. The specificity of these changes depends on the normalcy of the resting ECG. Right ventricular pacing produces major QRS and ST-T changes very similar to those of complete left bundle-branch block. They alter the resting ECG such that ischemic changes are considerably difficult to detect. Because of these resting abnormalities, ECG changes during treadmill exercise testing usually do not facilitate the diagnosis of ischemia or coronary artery disease. The following are two cases of ischemic ECG changes that occurred during right ventricular pacing. To our knowledge, there have been no reports of the classic ECG changes of ST-segment depression suggestive of ischemia which occurred during right ventricular pacing and which were discernible from the resting ECG changes.