Effect of right ventricular pacing on T and ST changes of the electrocardiogram in endogenous beats

38 patients with recurrent cardiotopic rhythm, treated by permanent "on demand" pacemaker, were investigated. 15 patients (group A) were observed for 14 days of pacing, 23 (group B) were observed from 7 to 68 months of pacing. Further, 17 persons were investigated--in 12 of them the endocardial electrode USCI had been placed in the right ventricle and left there for 24 hours. 10 persons were paced by endocardial bipolar USCI electrode from external pacemaker, the other two by unipolar electrode from permanent "on demand" pacemaker. In paced patients a negative deep T inversion and ST depression were observed. In persons paced for 24 hours the ST-T changes disappeared at the earliest 48 hours after pacing was stopped. Changes in repolarization caused by artificial depolarization should be taken into account when in patients with ventricular pacing and cardiotopic rhythm subendocardial infarction is suspected.