Oral
hydralazine has been shown to be effective in decreasing pulmonary arteriolar resistance and increasing cardiac output in some patients with
primary pulmonary hypertension. To determine whether a similar response could be observed in patients with chronic
cor pulmonale, the hemodynamic status before and after the
oral administration of
hydralazine (25 mg, then 50 mg every 6 hours for 48 hours) were evaluated in 12 patients at rest and in 8 during upright exercise. After
hydralazine, there was an increase in cardiac output at rest, from 4.3 to 6.3 liters/min (p < 0.001), and reductions in arteriovenous
oxygen difference, from 8.1 to 6.1 volume percent (p < 0.001), mean pulmonary arterial pressure, from 52 to 44 mm Hg (p < 0.01), and pulmonary arteriolar resistance, from 11.2 to 6.2 units (p < 0.0005). Similar hemodynamic changes occurred during exercise, including an increase in pulmonary arterial saturation from 27 to 39 percent (p < 0.001) and a decrease in total pulmonary resistance from 12.7 to 8.9 units (p < 0.01). Results of pulmonary function tests performed before and after
hydralazine did not change with
drug administration. These findings indicate that the lung vascular bed in some patients with
cor pulmonale is capable of responding to
hydralazine with a reduction in pulmonary resistance and an increase in cardiac output both at rest and during exercise.