ELECTROCARDIOGRAM R-WAVE AMPLITUDE CHANGES DURING RAPID ATRIAL-PACING - RELATION TO LEFT-VENTRICULAR DIMENSION CHANGES AND ST-SEGMENT CHANGES IN PATIENTS WITH CORONARY-ARTERY DISEASE

Changes in electrocardiogram R-wave amplitude often are noted during exercise in patients with coronary artery disease. The mechanism of this change is still unknown, though a relation to left ventricular dimension changes and/or myocardial ischaemia has been suggested. To evaluate the relation between these parameters we investigated 11 males (age: 49.5 +/- 6.3 years) suffering from coronary artery disease before, during and after rapid atrial pacing. Starting with 90 beats/min pacing rate was increased by steps of 10 beats/min every 3 minutes up to 130 beats/min. Data were obtained by simultaneous recording of transthoracic echocardiography and electrocardiogram. During atrial pacing a significant ST-segment depression and a significant reduction of enddiastolic left ventricular dimension were observed. The R-wave did not change significantly. R-wave amplitude increased in 3 (27.3%), decreased in 6 (54.5%) and remained unchanged in 2 (18.2%) patients. We conclude that R-wave amplitude changes are not explained by variations of left ventricular dimension and are not correlated to the level of myocardial ischaemia.