Carvedilol versus metoprolol in patients undergoing direct percutaneous coronary interventions for myocardial infarction: effects on QT dynamicity.

Beta-adrenergic blockers exert significant antiarrhythmic activity during ischemia and reperfusion. To further explore the beneficial effects conferred by alpha-1-adrenoceptor blockade on ventricular repolarization dynamicity in the acute phase of myocardial infarction (AMI), we compared carvedilol with metoprolol in the setting of primary percutaneous coronary intervention (PCI). In a prospective study, 100 consecutive patients undergoing primary PCI for AMI were randomized to metoprolol 200 mg/day versus carvedilol 25 mg/day. The first oral dose of study drug was administered and a 24-hour ambulatory electrocardiogram recorded upon hospital admission. Slopes of the linear QT/RR regression were determined before and after reperfusion. A total of 38 recordings of patients treated with metoprolol and 34 recordings of patients with carvedilol were eligible for analysis of QT/RR slopes. The two study groups were similar with respect to age, gender, TIMI perfusion grades, ventricular function, duration of ischemia, and site and size of infarction. Mean RR- and QT-intervals were similar to the metoprolol and carvedilol groups, before and after PCI. Likewise, there was no significant difference in QT/RR slopes between the metoprolol and carvedilol groups before PCI. In contrast, after PCI, there was a trend toward lower QT/RR slopes in the metoprolol group (from 0.18 +/- 0.07 to 0.17 +/- 0.08), and a significant decrease in QT/RR slopes in the carvedilol group (from 0.17 +/- 0.07 to 0.14 +/- 0.09). In patients undergoing successful direct PCI for AMI, treatment with carvedilol, in contrast to metoprolol, was associated with a significant decrease in QT-RR slopes, suggesting greater cardiac electrical stability.