[Therapy of primary pulmonary hypertension with phentolamine]

The effect of phentolamine was studied in 5 patients with pulmonary hypertension, of whom 3 had primary pulmonary hypertension and 2 had secondary pulmonary hypertension after pulmonary embolism. They received intravenous phentolamine in doses of 0.5 mg/min to 2 mg/min (i.e. up to a total dose of 27.5 mg in 25 minutes) during diagnostic cardiac catheterization. Under phentolamine infusion only 2 of the 3 patients with primary pulmonary hypertension showed a significant rise in cardiac index, from 1.4 to 2.0 and from 1.8 to 2.2 l/min/m2 respectively, a fall in pulmonary artery mean pressure from 100 to 93 and from 42 to 33 mm Hg respectively, and a decrease in pulmonary vascular resistance from 2950 to 1900 and from 1160 to 725 dyn X sec X cm-5 respectively. In 1 patient with primary, and 2 patients with secondary pulmonary hypertension, infusion of phentolamine had no effect. Interestingly, in the two patients with primary pulmonary hypertension who responded well to phentolamine the condition was very severe. It appears that even in cases with very advanced primary pulmonary hypertension there is a vasospastic component which can be influenced by vasodilators.