The effect of acute and chronic nitrate administration in precapillary and postcapillary pulmonary hypertension

The effect of nitrates was monitored in 16 patients with precapillary, and in 12 patients with postcapillary pulmonary hypertension (PH). The patients had haemodynamic examination on acute administration of 10 mg of isosorbide nitrate (ID) in infusion and after 2-month therapy with 120 mg of isosorbide dinitrate retard daily. Acute ID administration decreased filling pressure of both ventricles, pulmonary and aortic pressure, pulmonary and systemic resistance and increased blood flow. No significant difference was found between the two types of PH. Long-term administration resulted in a statistically significant decrease in filling pressure (in both ventricles) and pulmonary pressure, even though the decrease was less pronounced than those seen following acute administration. Again, no statistical differences were noted between the two types of PH. While acute administration of nitrates decreases both preload and afterload, chronic administration decreases only preload. The implications of this finding for therapeutic practice are discussed.