The role of isoproterenol in pulmonary artery hypertension of unknown etiology (primary): short- and long-term evaluation.

The experience derived from the administration of isoproterenol in six patients with pulmonary hypertension of unknown etiology (PAH-UE) is presented. The diagnosis was made after exclusion of other known diseases capable of producing hypertension in the pulmonary circuit. Catheterization was performed, and basal cardiopulmonary parameters, mean pulmonary artery pressure (PAP), pulmonary arteriolar resistance (PAR), cardiac index (CI), alveolar-arterial oxygen tension difference P(A-a)O2, and PaO2 were investigated. The effect of infusing 3 micrograms/min of isoproterenol into the pulmonary artery was studied in five cases. Isoproterenol was given sublingually to one patient who had previously received it intravenously; in another case it was given only sublingually. Significant P values (P less than .05) as a group were obtained, in relation to heart rate, CI, PAR, and mean PAP after isoproterenol. A favorable effect on the heart and lungs was seen in two cases, maintained for three years with sublingual isoproterenol with a favorable cardiorespiratory effect. Use of isoproterenol in PAH-UE is justified at present in those cases with a favorable cardiopulmonary response while no specific therapy is available.