Coltart D J
Postgrad Med J. 1976;52 Suppl 4:47-55.
The pressure-volume relationship of the intact human ventricle during ischaemia and following the administration of a drug commonly used to treat ischaemic heart disease has been studied. Precise quantitation of the effects of the non-selective beta-adrenergic blocking drug propranolol (0-15 mg/kg body weight) on left ventricular function, segmental wall motion and diastolic pressure-volume relationship in man has been performed. High fidelity left ventricular pressure measurements and simultaneous single-plane angiograms were recorded and volumes calculated by a light-pen computer system. Patients were transvenously atrially paced for constancy of heart rate during drug infusion or paced to angina. In patients with coronary heart disease paced to angina, logarithmic pressure-volume relationship showed change in slope (P greater than 0-05) of the regression line and upward shift in intercept b (+0-25; P greater than 0-001). The diastolic effects of propranolol may include substantial increases in ventricular volumes in those patients with impaired cardiac function. With respect to the intact human ventricle, propranolol may increase diastolic volume for a given level of ventricular pressure. Thus, in a static sense, the ventricle in these patients could be viewed as being more compliant following propranolol administration. However, the fact that the length-tension relationship as measured by the slope of the logarithmic pressure versus volume plot is unaltered by propranolol, suggests that the muscle comprising the ventricle itself exhibits no alteration in its passive elastic properties.
