Improvement of myocardial oxygenation is a major goal in the treatment of ischemic heart disease. Propranolol, 0.1 mg/kg intravenously, was administered to 20 patients in the acute state of myocardial infarction without clinical evidence of left ventricular failure. The most important hemodynamic response was a substantial decrease in myocardial contractility. This was reflected by a fall i cardiac index (average of 0.6 L/min/M2, P < 0.001) and of arterial mean pressure (average of 16 mm Hg, P < 0.001) with little change in systemic vascular resistance. Decrease in cardiac index was due mainly to decrease in stroke volume. Heart rate, not strikingly increased at the control state in the majority of patients, decreased an average of 7 beats/min (P < 0.001). Pulmonary wedge pressure rose an average of 2 mm Hg (P < 0.05). It remained unchanged or decreased in three patients. These varying but small changes in wedge pressure in the presence of decreased contractility may be related to improved left ventricular compliance, produced by propranolol. Propranolol markedly improved myocardial metabolism. Arterialcoronary sinus oxygen difference decreased an average of 0.72 ml/100 ml (P < 0.001); coronary sinus oxygen tension increased an average of 2 mm Hg. Myocardial lactate production shifted to extraction (average of -8% to 14%) or the rate of lactate extraction increased (average of 20% to 29%). Coronary blood flow decreased an average of 13 ml/100 g/min (P < 0.001). Both decrease in mean aortic pressure and decrease in myocardial oxygen requirements probably contributed to the fall in coronary blood flow. The finding, that myocardial metabolism improved, suggests that reduction in myocardial oxygen demand outweighed the decrease in coronary blood flow. None of the 20 patients developed left ventricular failure or other complications related to beta-adrenergic blockade. Severe chest pain, unresponsive to conventional therapy in four patients, was relieved by propranolol.These findings demonstrate that acutely administered propranolol improves myocardial oxygenation in patients with uncomplicated acute infarction without endangering perfusion of other vital organs.

The experiments were performed on open-chest mongrel dogs, the hearts being paced at a constant rate. Both vagi were cut in the neck and the peripheral ends were stimulated with frequencies of 1, 5, 10, 15, 20, 25, 30, 35, 40 and 50 cycles per sec (30 sec, 8 V, 2 msec). Adrenergic beta-receptors were blocked with propranolol and adrenergic alpha-receptors with dihydroergotamine. Coronary flow was measured with electromagnetic flowmeters on the descending branch of the left coronary artery. A significant increase in coronary flow was observed with rising frequency of stimulation. This increase was 15 percent with 30 Hz and decreased with higher frequencies. The total coronary resistance reached its lowest level at the frequency of 30 cycles per sec. The results clearly indicate the parasympathetic control of myocardial blood flow.

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