Beta-Blockers for Acute Myocardial Infarction - Essay Example

The subjects - survivors from a first AMI, were randomly assigned to two treatments. Thirty-seven patients received 100 mg metoprolol (a beta-blocker) per day whereas 34 patients received placebo. Before the study was conducted, a 24-hour ambulatory ECG was performed on each subject. This was repeated after 4 weeks of therapy. QT and RR intervals were determined through a computer program and the QT/RR relationship was described in terms of linear regression. The results showed that the regression lines significantly differed between the two study groups and metoprolol reduced the QT/RR slope.

The authors concluded that long-term beta-blockade in MI patients results in "a reduction of the QT/RR slope with a prolongation of the QT interval at higher rates" (Hintze et al., 1998). This implies that patients treated with beta-blockers may benefit from decreased susceptibility to life-threatening arrhythmias. A subsequent study by Bonnemeier, Ortak, Tlg, Witt, Schmidt, Wiegand et al. (2005) compared the effects on QT-dynamicity of two beta-blockers - carvedilol and metoprolol in patients undergoing percutaneous coronary interventions (PCI) for MI.

Data from 38 patients treated with metoprolol 200 mg/day and 34 patients treated with carvedilol 25 mg/day were subjected to QT/RR slope analyses. The data were gathered from a 24-hour ambulatory ECG recorded upon hospital admission and slopes of linear QT/RR regression were calculated before and after reperfusion. The results demonstrated no significant difference between the QT/RR slopes of the two groups before PCI. After PCI however, "there was a trend toward lower QT/RR slopes in the metoprolol groupand a significant decrease in the QT/RR slopes in the carvedilol group" (Bonnemeier et al.,. This essay states that in the list of leading causes of U.S. deaths, heart disease ranks first and stroke ranks third.

The British Heart Foundation states that myocardial infarction, also known as heart attack or coronary thrombosis, is a disease wherein the heart suddenly loses its blood supply. If not treated immediately, it can lead to the death of the affected area and consequently, the cessation of all heart functions. Most MIs happen to people over 50 and the incidence is higher in men than in women. Several treatments are available including aspirin and other platelet drugs, emergency angioplasty, heparin, and beta-blocker drugs.

The term “beta-blocker” is a short form of “beta-adrenergic receptor blocking agents”. When used to treat acute myocardial infarction, it reduces oxygen supply, which is beneficial since this decreases myocardial workload and oxygen demand. Once a person has undergone an MI, beta-blocker is required for life. The results of the study showed that there was no significant difference in the incidence of MI between atenolol, placebo and other hypertensives. While the risk of stroke was 19% lower in the beta-blocker group, there were no differences noted for MI or all-cause mortality.

Recent clinical trials suggest that beta-blockers are linked with increased risk of type-2 diabetes. However, beta-blockers are still valuable for heart rate control in patients with tachyarrhythmias and that the studies that contradict the effectiveness of beta-blockers do not apply to new ones.