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Exercise reduces persistent ductus arteriosus shunting in piglets
Insights
Dynamic exercise reduces shunting through a persistent ductus arteriosus in piglets. This prevents abnormal blood flow to the heart muscle during exercise.
Area of Science:
- Cardiovascular Physiology
- Pediatric Cardiology
- Exercise Science
Background:
- A persistent ductus arteriosus (PDA) can cause abnormal blood flow.
- The impact of dynamic exercise on PDA shunting and organ perfusion is not fully understood.
Purpose of the Study:
- To investigate the effects of dynamic exercise on left-to-right shunting through a PDA.
- To assess myocardial and skeletal blood flow distribution during exercise in the presence of a PDA.
Main Methods:
- A PDA was surgically created in neonatal piglets.
- Measurements of cardiac output, organ blood flow, and PDA shunting were taken at rest and during treadmill exercise.
- Radiolabeled microspheres were used to quantify blood flow distribution.
Main Results:
- Exercise did not worsen the subendocardial to subepicardial blood flow ratio in piglets with a PDA.
- PDA shunting significantly decreased during exercise (34% to 18%).
- Effective left ventricular output was maintained, similar to control animals.
Conclusions:
- Reduced PDA shunting during exercise is mediated by decreased systemic vascular resistance.
- Maintenance of effective left ventricular output and reduced shunting prevents myocardial perfusion abnormalities in swine with PDA during dynamic exercise.
Abstract:
To determine the effects of dynamic exercise on ductal left to right shunting and skeletal and myocardial blood flow distribution, a persistent ductus arteriosus was created by balloon catheters in neonatal piglets. At 8-10 weeks of age, aortic, pulmonary artery, and left atrial catheters were placed and radiolabelled microspheres injected for measuring left ventricular output, organ blood flows, and ductus left to right shunting at rest and during treadmill exercise (1.6 mph). At rest, effective left ventricular output and myocardial and skeletal muscle blood flows were similar in the study group and controls. Exercise increased skeletal muscle and left ventricular blood flows similarly in the control and study group and did not accentuate the exercise induced small reduction in the left ventricular subendocardial to subepicardial blood flow ratio. This was due to a significant reduction in the ductus left to right shunt during exercise (mean(SD) 34(15) vs 18(7)%, p less than 0.02) and maintenance of effective left ventricular output in the study group (447(144) vs 446(98) ml.min-1.kg-1 in controls). The reduction in ductus shunting during exercise was due to a significant decrease in systemic vascular resistance and a small increase in pulmonary vascular and ductus resistance. Thus, reduced persistent ductus arteriosus shunting and maintenance of effective left ventricular output prevents myocardial perfusion abnormalities during dynamic exercise in swine with a persistent ductus and small to moderate left to right shunts.