Haemodynamic requirements for an ideal pulmonary vasodilator.

An ideal vasodilator should be selective for the pulmonary vascular bed, thus minimizing side-effects from reduced systemic resistance. It must achieve not only a drop in pulmonary vascular resistance but also a marked decrease in pulmonary arterial pressure. The ideal drug should increase cardiac output and pulmonary venous oxygen saturation. An increase in oxygen delivery to the peripheral tissues should be achieved at a lower right ventricular afterload both at rest and during exercise. Right ventricular function should be improved. The effects of vasodilator therapy should be so marked that it should be possible to follow them non-invasively by radionuclide methods and exercise tolerance tests. The aim of vasodilator therapy is a regression of pulmonary hypertension and of right ventricular hypertrophy, an improved quality of life, and above all a longer survival.