Action of Bradykinin on Human Pulmonary Circulation

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Abstract
Twenty-one patients with pulmonary hypertension secondary to rheumatic mitral valve disease were submitted to right and left heart catheterization and received a continuous intravenous infusion of synthetic bradykinin (average dose, 0.98 µg/kg/min). The drug elicited an appreciable fall of the systemic vascular resistance simultaneously with a decrease of the mean systemic arterial pressure and an increase of the cardiac output in all cases. The rise in cardiac output derived mainly from an increase in heart rate, since the modifications of the stroke volume were generally of low magnitude. In the pulmonary circulation, the increase in blood flow was coincident with a rise of the mean arterial and venous (left atrial) pressures in 19 and all patients, respectively. The pulmonary vascular resistance fell in 19 patients, but no appreciable modifications were noted in pulmonary blood volume. The changes in the lesser circulation were interpreted as expressing secondary effects, either mechanical or reflex, consequent to the action of bradykinin on the systemic vessels and heart rather than a direct effect of the drug on the pulmonary vessels.