BackgroundPulmonary hypertension results in increased morbidity and mortality in children after surgical repair of congenital heart defects. Various vasodilators have been unsuccessful in providing preferential pulmonary vasodilation in these patients. Identification of a more preferential pulmonary vasodilator would improve the assessment, management, and outcome of these children. To determine whether ATP-MgCl2is a preferential pulmonary vasodilator in children with pulmonary hypertension secondary to congenital heart defects, ATP-MgCl2was administered during routine cardiac catheterization, and the effects were compared with tolazoline. In addition, ATP-MgCl2was infused intravenously during episodes of postoperative pulmonary hypertension.Methods and ResultsDuring cardiac catheterization in 28 children, the effect of ATP-MgCl2on the pulmonary artery pressure (PAP) and pulmonary vascular resistance index (Rp) was compared with tolazoline. ATP-MgCl2(0.1 mg of ATP per kilogram per minute) decreased mean PAP by 24% (P<.05) and Rpby 47% (P<.05) without changing mean systemic arterial pressure or systemic vascular resistance. These effects were comparable to those of tolazoline (1 mg/kg). ATP-MgCl2produced no significant side effects; tolazoline caused tachycardia, nausea, and vomiting. After cardiac surgery in 7 patients, ATP-MgCl2decreased PAP by 14% (P<.05) and systemic arterial pressure by 6% (P<.05) and eliminated pulmonary hypertensive crises in 3 of 3 patients.ConclusionsATP-MgCl2is a safe, effective, and preferential pulmonary vasodilator in children with pulmonary hypertension secondary to congenital heart defects. It is useful for evaluating pulmonary vasoreactivity during cardiac catheterization and for treating pulmonary hypertension after cardiac surgery.