Background: Angiotensin-converting enzyme (ACE) inhibitors have been shown to improve the mortality rate in patients with congestive heart failure. The exact mechanism of this effect is uncertain. Signal-averaged electrocardiography has been used to evaluate the presence of late potentials as a marker for sudden cardiac death. We examined prospectively the effects of ACE inhibitor therapy on signal-averaged ECGs and ventricular arrhythmia frequency in 20 patients with moderate to severe left ventricular dysfunction and symptomatic congestive heart failure.
Methods: A signal-averaged ECG and 24 h Holter monitor were performed immediately before and both 1 week and 6 weeks after captopril initiation. The mean dose of captopril at 6 weeks was 38 +/- 31 mg. The patients (19 men and one woman, mean age 63 +/- 12 years) had a baseline ejection fraction of 22 +/- 7% and mean functional class of 2.6 +/- 0.5. The cause of congestive heart failure was coronary artery disease in 18 patients, idiopathic cardiomyopathy in one, and valvular disease in one.
Results: All three signal-averaged ECG time-domain parameters tended to improve over the course of the study (study 1, 2, 3: QRS duration (ms) = 108 +/- 11, 106 +/- 12, 105 +/- 11; low-amplitude signal duration (ms) = 30 +/- 8, 31 +/- 10, 28 +/- 10; root mean voltage (microV) = 33 +/- 20, 37 +/- 24, 40 +/- 2, respectively). These changes were not statistically significant, although the improvement in QRS duration was nearly so with P = 0.06. The occurrence and complexity of ventricular ectopy did not appear to be consistently altered.
Conclusion: ACE inhibitor therapy with captopril did not appear to alter ventricular ectopy over the course of this study. However, the trends toward improvement of signal-averaged ECG parameters deserve further evaluation in a larger and longer-term study.