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Hemodynamic effects of the cardioselective beta-blocking agent metoprolol in acute myocardial infarction. A 24-hour
Abstract:
Hemodynamic changes were studied in ten patients with uncomplicated transmural myocardial infection during 24 hours on beta-blockade. The cardioselective beta-adrenergic blocking drug metoprolol was injected (15 mg i.v.) within the first 24 hours after onset of chest pain and was followed by oral therapy (25-50 mg at 6-hour intervals). There was a decrease in heart rate, systolic BP, and cardiac output, which was most marked after the injection. The stroke volume and diastolic BP for the whole group of patients remained unchanged. The pulmonary artery end diastolic pressure did not change significantly after the injection but a continuous fall was obtained in three out of four patients with initially elevated values. The preejection period, measured from the ECG and carotid pressure curve, as initially short and was prolonged in all patients after administration of the beta-blocking drug. It is concluded that the cardioselective beta-blocking drug metoprolol may be used in selected patients in the acute phase of myocardial infarction without danger of hemodynamic deterioration during the first 24 hours of therapy. The selection of patients can be based on clinical criteria. In this study signs of left heart failure, hypotension, poor peripheral circulation, bradycardia, and AV block were regarded as contraindications.
Insights
Metoprolol, a beta-blocker, can be safely administered in the acute phase of myocardial infarction. This study shows it does not cause hemodynamic deterioration in selected patients within 24 hours.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Myocardial infarction (MI) management requires careful consideration of hemodynamic stability.
- Beta-adrenergic blockade is a cornerstone therapy in cardiovascular disease.
Purpose of the Study:
- To evaluate the hemodynamic effects of early metoprolol administration in acute myocardial infarction.
- To determine the safety of metoprolol in the first 24 hours post-MI.
Main Methods:
- Ten patients with uncomplicated transmural MI received intravenous metoprolol followed by oral therapy.
- Hemodynamic parameters including heart rate, blood pressure, cardiac output, and pre-ejection period were monitored.
Main Results:
- Metoprolol administration led to decreased heart rate, systolic blood pressure, and cardiac output.
- Stroke volume and diastolic blood pressure remained unchanged; pre-ejection period prolonged.
- Pulmonary artery end-diastolic pressure showed a trend towards decrease in patients with elevated initial values.
Conclusions:
- Early use of cardioselective metoprolol is safe in selected acute MI patients within 24 hours.
- Patient selection is crucial, excluding those with heart failure, hypotension, poor circulation, bradycardia, or AV block.