Double-blind study of the effect of cardioselective beta-blockade on chest pain in acute myocardial infarction.

A double-blind study including three different cardioselective beta-blockers, practolol, H 87/07 and metoprolol, was performed in 54 patients with acute myocardial infarction and chest pain shortly after onset of symptoms. Transmural infarctions were found in 42 patients while 12 patients had nontransmural infarctions. Chest pain and the product of heart rate and systolic blood pressure were significantly reduced in the beta-blocker groups whereas no changes were seen after saline. All patients with nontransmural infarctions and 14 out of 29 with transmural infarctions got pain relief lasting for at least 30 min. None of the patients developed signs of left ventricular backward failure, shock, or bradycardia. A decrease in ST segment elevation was observed in all the transmural infarctions after beta-blockade. No changes in ST segment elevation were found after analgesics when given after saline, but in some cases an increase was seen in this parameter when analgesics were given due to insufficient pain relief after beta-blockers or due to return of chest pain. It is suggested that pain relief by beta-blockers indicates decrease of myocardial ischemia.