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Effects of Single Ventricle Physiology with Aorto-Pulmonary Shunt on Regional Myocardial Blood Flow in a Piglet Model
M. Ricci, P. Lombardi, A. Galindo, s. Schultz, A. Vasquez, E. Rosenkranz. University of Miami Miller School of Medicine, Miami, FL,
Background
In single ventricle physiology (SVP) with aorto-pulmonary connection, diastolic hypotension could alter regional myocardial blood flow (MBF). Also, afterload augmentation could impair MBF, causing subendocardial malperfusion. We studied the effects of acute SVP on regional MBF distribution and the consequences of afterload augmentation on MBF.
Methods
SVP was created in 8 newborn pigs, while 8 animals served as sham-controls. Aorto-pulmonary shunt, echo-guided atrial septostomy, tricuspid valve avulsion, and pulmonary artery occlusion allowed the left ventricle to support systemic and pulmonary circulations. Aortic balloon inflation was used to increase afterload. Microsphere determination of MBF to was obtained at baseline and during SVP (30min, 120 min, afterload ).
Results
Arterial O2 content, diastolic pressure, and CPP declined in SVP (p<0.05). Acute SVP caused higher MBF (p<0.05), unchanged subendocardial/subepicardial flow ratio and O2 delivery, and lower coronary resistance (p<0.01)(Figure). Afterload augmentation increased CPP, causing a trend for higher MBF and O2 delivery (p=ns), without affecting subendocardial/subepicardial flow distribution. Oxygen supply/demand fell in SVP, remaining unchanged during afterload augmentation.
Conclusions
Our study demonstrates that in acute SVP with aorto-pulmonary shunt, MBF is maintained by lower coronary resistance. SVP results in less favorable O2 supply/demand, although normal transmural MBF distribution is maintained. Techniques that avoid diastolic run-off (SVP with RV-PA conduit) could improve coronary reserve. Moderate afterload augmentation did not induce subendocardial malperfusion, nor did it worsen O2 supply/demand.
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