Effects of intracoronary low-dose enalaprilat on ventricular repolarization dynamics after direct percutaneous intervention for acute myocardial infarction

Background: Data from animal models suggest that inhibition of angiotensin converting enzymes result in an increased ventricular electrical stability after reperfusion in acute myocardial infarction (MI). As electrical stability is largely dependent on ventricular repolarization, we sought to determine the impact of low-dose intracoronary (ic.) application of enalaprilat (EN) as an adjunct to direct primary coronary intervention (PCI) on QT dynamics in the acute phase of MI.
Methods: Twenty-two consecutive patients with a first acute MI who underwent successful direct PCI (TIMI 3 flow) were randomized to ic. EN (50 μg) or placebo/saline (PL), given immediately after reopening of the infarct vessel. On hospital admission, a 24-hour-Holter-electrocardiogram (ECG) was initiated. Slopes of the linear QT/RR regression were determined for the time intervals before reperfusion and after reperfusion.
Results: A total of 7 patients in the EN group and 8 patients in the PL group had valid ECG recordings for beat-to-beat QT analysis. Mean RR interval and mean QT interval were not significantly different between the EN and the PL groups both before and after PCI. There were also no significant differences regarding QT/RR slopes between EN and PL groups before PCI. After PCI, QT/RR slopes significantly decreased in the EN group (0.169 ± 0.04 to 0.121 ± 0.03; P < 0.01), whereas there were no significant alterations in the PL group (0.175 ± 0.04 to 0.171 ± 0.03; P = ns).
Conclusions: Intracoronary EN therapy as an adjunct to direct PCI significantly decreases QT/RR slopes, suggesting a normalization of the coupling between heart rate and repolarization by improving electrical restitution. Thus, our findings offer new insights into possible beneficial effects of ACE inhibition on cardiac electrical stability in acute MI.