Reduction of enzyme levels by propranolol after acute myocardial infarction.

Abstract

SUMMARY The effect of propranolol (0.1 mg/kg intravenously followed by 320 mg given over 27 hour orally) on serum levels of creatine kinase enzyme was studied in a randomized trial involving 95 patients seen within 12 hours of onset of symptoms of uncomplicated myocardial infarction. In 15 patients who were treated with propranolol within 4 hours of onset, and who eventually developed pathological Q waves, peak measured enzyme levels were 27% (P < 0.0125) lower than in 19 control patients who were also seen THE WELL-KNOWN EFFICACY of beta-adrenergic blocking drugs for the treatment of angina pectoris53 suggests that these drugs should also be effective for the acute imbalance between oxygen supply and demand which occurs during the early stages of myocardial infarction. Apart from an encouraging report by Snow in 1965,4 however, a number of carefully randomized early clinical trials of beta blockers5-9 showed no effect on hospital mortality from infarction nor on the incidence of arrhythmias in treated patients compared with controls.A number of recent developments suggest, however, that the use of beta-adrenergic blocking drugs in the acute stage of myocardial infarction should be re-investigated. First, there is the evidence that long-term beta blockade prolongs life after myocardial infarction'0 11 and that this may be due in part to the prevention of new ischemic events.'2 Second, there is evidence that propranolol given prophylactically to experimental animals reduces myocardial infarct size;3-5 this suggests that measurements of infarct size should be used as an end-point for therapeutic trials in man. Third, doses of propranolol used in previous trials (40-80 mg per day) were comparatively low and were administered orally and comparatively late after the onset. Patients given this low dose do not develop blood levels within the therapeutic range for 24-48 hours after first administration of the drug. 16The present trial proposed to investigate the effect of highloading doses of propranolol given within 12 hours of onset of symptoms of infarction on serum creatine phosphokinase (CPK) levels.'7', Results show that CPK levels were reduced by propranolol if the drug was given within four hours of onset of the most severe chest pain.Patients and MethodsWe included in this study those infarctions which were of moderate severity since we postulated they would ultimately within 4 hours of the onset but had no specific treatment. Total calculated enzyme appearance was also lower in the treated patients (reduced 25%, P < 0.05) as was the calculated rate of appearance (33%, P < 0.005). No significant difference was found for treated compared with control patients entering the trial more than 4 hours after the onset of chest pain. This evidence suggests that propranolol may reduce the size of uncomplicated infarctiops if it is given intravenously within 4 hours of the onset.cause a moderately high enzyme release for which a reduction would be both easily measurable and clinically meaningful. At the same time it was r...

Labetalol infusion in acute myocardial infarction with systemic hypertension.

“…The advantages of treating myocardial infarction with systemic hypertension, a situation associated with high serum catecholamine levels, by adrenoceptor blockade, were not apparent in a previously described (Kelly et al, 1973) (Peter et al, 1978). Similarly, problems have been encountered with other pharmacological agents.…”

“…However, ac-adrenoceptor blockade with phentolamine in these circumstances is relatively ineffective in reducing systemic BP in those patients with pre-existing hypertension and, moreover, while satisfactorily lowering left ventricular end diastolic BP, increases heart rate and can worsen myocardial ischaemia (Kelly et al, 1973). padrenoceptor blockade on the other hand lowers systemic BP and heart rate, but may elevate left ventricular filling pressure (Peter et al, 1978).…”

Propranolol decreases sympathetic nervous activity reflected by plasma catecholamines during evolution of myocardial infarction in man.

“…Therefore, beta adrenergic blockade has gained increasing interest as therapeutic intervention in the acute state of myocardial infarction. Propranolol has been shown to be beneficial in experimental coronary occlusion (7) and in human myocardial infarction for a selected patient group (8)(9)(10). Recent studies have demonstrated, however, that propranolol increased plasma catecholamine contents in several clinical conditions (11)(12)(13), and thus caused concern about its use in acute myocardial infarction.…”

Propranolol during the evolution and subsequent ten days of myocardial infarction in man: Hemodynamic, initial cardiac energetic, and neurohumoral responses

“…Using serial serum creatine kinase (CK) measurements, all events of the CK time-activity curve (rise, peak, and decay) occurred significantly later compared to those of the untreated group. Peter et al (62) demonstrated in a randomized trial of patients with uncomplicated myocardial infarction that both peak serum CK levels and total calculated serum CK appearances were significantly reduced by approximately 30% if propranolol was given intravenously in a dose of 0.1 mg/kg within 4 h of the onset of chest pain. In a later study on 20 randomly selected patients within 4 h of the onset of suspected myocardial infarction, propranolol adminstration (0.1 mg/kg i.v.…”