Effects of isoproterenol on the pulmonary blood volume in patients with valvular heart disease and primary myocardial disease

The effects of intravenous isoproterenol upon the pressure-flow-volume relationships in the pulmonary vascular bed were studied in 34 patients and one normal subject during simultaneous right and transseptal left heart catheterization. In five patients with primary myocardial disease and in one normal subject, active pulmonary vasodilation was demonstrated by a significant increase in pulmonary blood volume (PBV) and a concomitant fall in pulmonary vascular distending pressure (P D ). Infusion of the drug into 18 patients with mitral stenosis resulted in a concordant rise in PBV and PD, strongly suggesting passive distention of the pulmonary vascular bed. In contrast to the responses of these two groups of patients, isoproterenol infusion into 11 patients with aortic valve disease failed to change the PBV, but caused a significant decrease in P D . It is concluded that the response of different groups of patients to isoproterenol cannot be explained by a single mechanism. Multiple actions of the drug must be considered, including active pulmonary vasodilation, a positive inotropic action upon the heart, and bronchomotor effects.