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Afterload reduction by hydralazine in children with a ventricular septal defect as determined by aortic input
H Endo1, H Shiraishi, M Yanagisawa
1Department of Pediatrics, Jichi Medical School, Tochigi, Japan.
Insights
Hydralazine effectively reduced afterload in children with ventricular septal defects by lowering peripheral resistance and pulse wave reflection, leading to increased stroke volume.
Area of Science:
- Pediatric Cardiology
- Cardiovascular Physiology
Background:
- Ventricular septal defect (VSD) can lead to increased pulmonary blood flow and altered cardiac hemodynamics.
- Afterload reduction is a key therapeutic goal in managing VSD complications.
Purpose of the Study:
- To evaluate the acute effects of hydralazine on afterload reduction in pediatric patients with VSD.
- To assess changes in aortic input impedance, wall stress, and blood flow dynamics post-hydralazine administration.
Main Methods:
- Cardiac catheterization was performed on eight children (age 2.2-8.8 years) with VSD.
- Aortic input impedance, wall stress, and hemodynamic parameters were measured before and after hydralazine administration.
Main Results:
- Hydralazine significantly decreased mean aortic pressure, peripheral resistance, and pulse wave reflection.
- The pulmonary to systemic blood flow ratio decreased, while the pulmonary to systemic resistance ratio increased.
- End-systolic wall stress was significantly reduced, indicating improved ventricular afterload.
Conclusions:
- Hydralazine acutely reduces afterload in children with VSD by decreasing peripheral resistance and pulse wave reflection.
- This afterload reduction is associated with improved stroke volume and favorable hemodynamic changes.
Abstract:
Hydralazine was administered at cardiac catheterization to eight children with a ventricular septal defect (age: 2.2-8.8 years), and the extent of afterload reduction was determined using aortic input impedance and wall stress. The pulmonary to systemic blood flow ratio decreased from 2.2 +/- 0.8 to 1.8 +/- 0.4 (p < 0.05) and the pulmonary systemic resistance ratio increased from 0.11 +/- 0.08 to 0.13 +/- 0.10 (p < 0.05) after hydralazine administration. Hydralazine reduced mean aortic pressure and the amplitude of the late systolic peak of the aortic pressure wave. Peak flow velocity in the descending aorta increased from 62 +/- 14 to 81 +/- 24 cm/sec (p < 0.05). Peripheral resistance decreased significantly from 13.3 +/- 5.9 to 6.6 +/- 3.7 10(3) dyn sec/cm3 (p < 0.05). The modulus of the first harmonic, indicating pulse wave reflection, decreased from 1196 +/- 575 to 815 +/- 382 dyn sec/cm3 (p < 0.05). The characteristic impedance, indicating aortic stiffness, did not change. End-systolic wall stress decreased significantly from 54.4 +/- 16.7 to 34.8 +/- 10.2 g/cm2 (p < 0.01). Hydralazine acutely achieved afterload reduction by reducing both peripheral resistance and pulse wave reflection, and increased stroke volume.