Effect of Low Dosage Inhaled Nitric Oxide on Pulmonary Hypertension in Congenital Heart Disease.

An evaluation of the pulmonary vascular resistance and the reversibility of pulmonary vascular reaction in children with congenital heart disease is essential for determining the surgical indication and for assessing the long-term prognosis. We report the clinical efficacy of low dosage inhaled nitric oxide and investigate the relationship between its effect and hemodynamic parameters in 18 patients with congenital heart disease. The patients were divided into 3 Groups; Group 1 consisting of 3 patients with Eisenmenger syndrome, Group 2 of 10 patients whose mean pulmonary artery pressure was more than 30 mmHg, and Group 3 consisting of 5 patients whose mean pulmonary artery pressure was less than 30 mmHg. High concentration (90%) oxygen, and also normal oxygen (21%) containing 10 parts per million nitric oxide were administered by cardiac catheterization. In Group 1, both the 90% oxygen and the normal oxygen with nitric oxide showed no affect on the hemodynamical variables. In Group 2, the pulmonary artery pressure and the pulmonary vascular resistance both significantly decreased with the 90% oxygen, and with the nitric oxide inhalation, but these decreases were not found in Group 3. In the 15 patients (of Groups 2 and 3 combined) who were considered to have reversible pulmonary vascular changes, significant correlations were found between the baseline pulmonary artery pressure and the magnitude of pulmonary vasodilation. No clinical evidence of toxicity was seen with the administration of the inhaled nitric oxide. These data suggested that inhaled nitric oxide, even in a low dosage, was a potent and selective pulmonary vasodilator in patients with congenital heart disease complicated with pulmonary hypertension. Since a positive correlation was found between the baseline pulmonary artery pressure and the magnitude of pulmonary vasodilation, this examination demonstrated potential efficacy for objective analysis in patients with pulmonary hypertension.