The effect of glucagon on the coronary circulation in man

Glucagon, 300 µg/ minute, was infused intravenously over 15 minutes in 27 subjects. The patients were divided into three groups: group I, patients without heart disease; group II, patients with arteriosclerotic heart disease; and group III, patients with congestive heart failure. Hemodynamic measurements included observations on myocardial blood flow using bolus injections of 84 rubidium and a coincidence counting technic. Myocardial oxygen consumption was determined after coronary sinus intubation in nine of the 27 patients. Significant increases were noted in heart rate, mean arterial pressure, tension-time index/minute and left ventricular work. Myocardial blood flow increased significantly while myocardial oxygen extraction remained constant suggesting that the augmentation in blood flow was sufficient to meet the increased myocardial demands for oxygen. The effects of glucagon on the coronary circulation resemble that of isoproterenol rather than norepinephrine without, however, leading to the production of arrhythmias seen with these catecholamines.

A comparative study of nitroglycerin and propranolol

The action of sublingual nitroglycerin (0.6 mg) and intravenous propranolol (0.1 mg/kg) on shortening of right ventricular fibers was investigated in patients with and without coronary artery disease. This was accomplished with a newly devised strain gauge catheter. Hemodynamic parameters and changes in the oxidation-reduction potential of heart muscle were determined. Nitroglycerin results in decrease in shortening and velocity of shortening of ventricular fibers, heart rate, left ventricular end-diastolic and systemic pressure, dp/dt, tension-time index, stroke index, peripheral resistance, and left ventricular minute work in normal and arteriosclerotic subjects. Intravenous propranolol leads to a fall in velocity of shortening of myocardial fibers, heart rate, dp/dt, stroke index, and left ventricular minute work. However, there is an increase in tension-time index and peripheral resistance with no change in systemic pressure. Left ventricular end-diastolic pressure rises significantly in arteriosclerotic patients. The myocardial oxidation-reduction potential increases after nitroglycerin whereas it falls after propranolol in normal and arteriosclerotic patients.