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Effect of increase in heart rate on interatrial shunt in atrial septal defect
M Fukazawa1, J Fukushige, Y Ueda
1Department of Pediatrics, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Insights
Rapid heart rate increases in children with atrial septal defect lowered the pulmonary to systemic blood flow ratio. This finding may explain flow changes during exercise in these patients.
Area of Science:
- Pediatric Cardiology
- Hemodynamics
- Congenital Heart Disease
Background:
- Atrial septal defect (ASD) is a common congenital heart condition.
- Altered hemodynamics in ASD can affect systemic and pulmonary blood flow.
- Understanding the impact of heart rate on flow dynamics is crucial for managing ASD.
Purpose of the Study:
- To investigate the effect of increased heart rate on systemic and pulmonary blood flow in children with ASD.
- To determine the pulmonary to systemic blood flow ratio changes during atrial pacing.
- To explore the underlying mechanisms, including ventricular compliance, responsible for observed hemodynamic alterations.
Main Methods:
- Studied 20 children with ASD (mean age 9 years).
- Utilized atrial pacing to increase heart rate by 25% and 50%.
- Measured systemic and pulmonary blood flow changes and calculated the pulmonary to systemic flow ratio.
Main Results:
- Systemic blood flow increased by 13% and 27% with 25% and 50% heart rate increases, respectively.
- Pulmonary blood flow remained unchanged.
- The pulmonary to systemic blood flow ratio significantly decreased by -15% and -22%.
Conclusions:
- Rapid heart rate significantly reduces the pulmonary to systemic blood flow ratio in children with ASD.
- This reduction is likely due to differences in left and right ventricular diastolic distensibility.
- Increased heart rate may contribute to altered pulmonary to systemic flow ratios during exercise in children with ASD.
Abstract:
The effect of increases in heart rate by atrial pacing was investigated in 20 children [mean 9 +/- 4 (SD) years] with atrial septal defect. Systemic blood flow increased by 13 +/- 10 and 27 +/- 22% with a 25 and 50% increase in heart rate, respectively. Pulmonary blood flow, however, remained unaltered. Thus, rapid pacing decreased the pulmonary to systemic blood flow ratio significantly (-15 +/- 10 and -22 +/- 13%, respectively). This hemodynamic alteration was attributed to the difference in diastolic distensibility (compliance) between the left and right ventricles, and the ratio of right ventricular to left ventricular compliance (defined by dV/dP) near the end-diastolic pressure was estimated to be 6.5 +/- 4.2. It is suspected that the increase in heart rate may contribute to the lowering of pulmonary to systemic flow ratio during exercise in children with atrial septal defect.