THERAPY AND, PREVENTION CONGENITAL HEART DISEASE Short-term hemodynamic elfects of hydralazine in infants with complete atrioventricular canal defects

We evaluated the acute hemodynamic responses to hydralazine during cardiac catheterization in eight infants (ages 1.0 to 5.5 months) with congestive heart failure due to complete atrioventricular canal defect. Hydralazine administered intravenously (0.5 to 1.0 mg/kg body weight) increased heart rate and systemic blood flow and decreased mean right atrial pressure, systemic and pulmonic arterial pressures, systemic arteriolar resistance, and the ratio of pulmonary to systemic blood flow (p < .05). The percentage of pulmonary flow contributed by shunted blood (percent left-to-right shunt; measured by indicator dilution) was decreased by hydralazine in six (mean = 85% before to 64% after hydralazine; p < .01), but remained unchanged (79%) in two infants. The two infants with no change in percent left-to-right shunt had higher pulmonary arteriolar resistances (Rp) before hydralazine (mean = 12.8 vs 3.2 U/m2) and had greater declines in Rp (mean change 5. 1 vs + 0.3 U/i2) in response to hydralazine. Thus, if Rp does not fall, hydralazine reduces the percentage of left-to-right shunt over the short term and therefore might be useful for managing congestive heart failure in these infants. However, because the response varies, an evaluation of the short-term hemodynamic effects of hydralazine may be warranted in an attempt to select those infants who might respond favorably to long-term hydralazine therapy. Circulation 69, No. 5, 949-954, 1984. SUCCESSFUL MEDICAL MANAGEMENT of congestive heart failure can be difficult to achieve in infants with large systemic-to-pulmonary shunts.' Recent reports suggest that treatment with digoxin, a principal therapeutic agent for this condition,2 may not benefit a substantial number of these infants.3I It would be helpful to identify additional drugs that might provide hemodynamic improvement, especially in cases in which surgical intervention is not feasible. Vasodilators are commonly used to help control congestive heart failure in adults,5-9 but the experience in pediatric patients is mostly limited to children with depressed ventricular function either due to a congestive cardiomyopathyl'0" or occurring immediately after cardiac surgery. 12-14 Experiments in animals have demonstrated that reduction of the systemic vascular resistance with a vasodilator will decrease the magnitude of a left-to-right shunt across a ventricular septal defect. 15. 16 Presumably a reduction in left-to-right From the Division of Pediatric Cardiology, Vanderbilt University Medical Center, Nashville. Supported in part by Public Health Service National Research Service Award Institutional grant No. HL0741 1-05. Address for correspondence: Michael Artman, M.D., Department of Pediatrics, University of South Alabama Medical Center, 2451 Fillingim St., Mobile, AL 36617. Received July 18, 1983; revision accepted Jan. 11, 1984. Vol. 69, No. 5, May 1984 shunting would benefit infants with congestive failure due to a systemic-to-pulmonary communication with high pulmonary blood flow. However, conflicting results have been reported regarding the short-term effects of vasodilators administered to infants with ventricular septal defects. 17-20 Our study was designed to assess the short-term hemodynamic responses to hydralazine (an arteriolar dilator) in infants with left-to-right shunts and congestive heart failure. We chose to study infants with complete atrioventricular canal defects because many of these patients have heart failure that is refractory to conventional medical therapy. Methods Eight infants (four boys; four girls) with congestive heart failure and complete atrioventricular canal defects were the subjects of this study. Each infant was less than 6 months old and all had trisomy 21. Pertinent clinical characteristics of this group are summarized in table 1. All eight infants underwent cardiac catheterization to confirm the clinical diagnosis and to precisely define hemodynamic and anatomic abnormalities. The hemodynamic status was assessed before and after the intravenous administration of hydralazine. Informed consent was obtained from a parent or legal guardian. Digoxin and/or diuretics were not administered within 12 hr before catheterization. Six infants were sedated with 2 mg/kg meperidine, and 1 mg/kg hydroxyzine each given intramuscu949 by gest on A ril 8, 2017 http://ciajournals.org/ D ow nladed from