Acute effects of vasodilators on left-to-right shunts in infants and children.

Based on the favorable experience with vasodilator therapy in adult heart disease and the results of acute dogs experiments, we undertook the hemodynamic evaluation of hydralazine and phentolamine during diagnostic cardiac catheterization. We studied seven infants and children with left-to-right (leads to R) shunts at atrial, ventricular, or ductal levels to determine whether vasodilator therapy might be useful in the treatment of infants with congestive heart failure (CHF) due to large L leads to R shunts. Shunts, flows, and resistances were measured by the indicator dilution and Fick techniques before and after administration of the drug. At a dose sufficient to produce an effect, the shunt flow increased after each drug. There is no evidence from studies at cardiac catheterization of therapeutic efficacy for vasodilators in the treatment of CHF due to cardiac L leads to R shunts.