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Short-term hemodynamic effects of hydralazine in infants with complete atrioventricular canal defects
Insights
Hydralazine improved hemodynamics in infants with heart failure by reducing shunting and pressures. However, individual responses vary, suggesting short-term testing before long-term use.
Area of Science:
- Pediatric Cardiology
- Pharmacology
- Congenital Heart Disease
Background:
- Congestive heart failure in infants often results from congenital heart defects like complete atrioventricular canal defect.
- Managing heart failure in infants requires understanding drug responses and hemodynamic effects.
Purpose of the Study:
- To evaluate the acute hemodynamic effects of intravenous hydralazine in infants with congestive heart failure.
- To determine if hydralazine reduces left-to-right shunting in this population.
Main Methods:
- Cardiac catheterization was performed on eight infants (1.0-5.5 months) with congestive heart failure.
- Intravenous hydralazine (0.5-1.0 mg/kg) was administered, and hemodynamic parameters were measured.
- Indicator dilution was used to quantify the percentage of left-to-right shunt.
Main Results:
- Hydralazine increased heart rate and systemic blood flow, while decreasing pressures and systemic arteriolar resistance.
- The left-to-right shunt percentage decreased significantly in six infants (85% to 64%).
- Two infants with higher baseline pulmonary arteriolar resistance showed no change in shunt percentage.
Conclusions:
- Hydralazine can acutely reduce left-to-right shunting and improve hemodynamics in infants with complete atrioventricular canal defect.
- The variable response, particularly in infants with high pulmonary arteriolar resistance, necessitates individual hemodynamic assessment.
- Short-term evaluation of hydralazine's effects may guide selection for long-term therapy in pediatric heart failure.
Abstract:
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 less than .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 less than .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/m2) 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.