The effect of digitalis in compensated and decompensated patients with internal cardiac pacemakers

Nine elderly patients (average age of 77 years) with complete heart block who had internal fixed-rate cardiac pacemakers were studied in order to determine their response to ouabain in the resting and exercise states. Three patients were in clinical congestive heart failure, and all 3 manifested significant increases in resting and exercise cardiac indices after ouabain. None of the 6 patients who were not in clinical congestive heart failure had a significant increase in cardiac index after ouabain, and the exercise cardiac index was essentially the same before and after ouabain. In these elderly patients with complete heart block and fixed-rate internal pacemakers, digitalis appears to have improved cardiac function only in the presence of clinical congestive heart failure.