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Marco Ricci
Pierluca Lombardi
Alvaro Galindo
Eliot Rosenkranz
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Right arrow Congenital - cyanotic

J Thorac Cardiovasc Surg 2006;132:252-259
© 2006 The American Association for Thoracic Surgery

Surgery for Congenital Heart Disease

Effects of single-ventricle physiology with aortopulmonary shunt on regional myocardial blood flow in a piglet model

Marco Ricci, MD * , Pierluca Lombardi, MD, Alvaro Galindo, MD, Steven Schultz, MD, Amelia Vasquez, Eliot Rosenkranz, MD

Holtz Children's Hospital, University of Miami Miller School of Medicine, Miami, Fla

Read at the Thirty-second Annual Meeting of the Western Thoracic Surgical Association, Sun Valley, Idaho, June 21-24, 2006.

Received for publication October 21, 2005; revisions received March 10, 2006; accepted for publication March 20, 2006.

* Address for reprints: Marco Ricci, MD, Division of Cardiothoracic Surgery, University of Miami Miller School of Medicine, Holtz Center 3072 (R-114), 1611 NW 12th Ave, Miami, FL, 33136. (Email: mricci{at}med.miami.edu).

OBJECTIVES: In single-ventricle physiology with aortopulmonary connection, diastolic hypotension could alter regional myocardial blood flow. Also, afterload increases could impair myocardial blood flow by increased wall tension and relative subendocardial malperfusion. This study explores the effects of acute single-ventricle physiology on regional myocardial blood flow distribution and investigates the consequences of moderate afterload augmentation on myocardial blood flow.

METHODS: Single-ventricle physiology was created in 8 piglets without using bypass, and 8 animals served as a sham control group. Aortopulmonary shunt, echo-guided atrial septostomy, tricuspid valve avulsion, and pulmonary artery occlusion allowed the left ventricle to support systemic and pulmonary circulations. Afterload augmentation was produced by aortic balloon inflation. Physiologic recordings and stable-isotope microsphere determination of myocardial blood flow to the subepicardium and subendocardium were obtained at baseline and during single-ventricle physiology (at 30 minutes, 120 minutes, and afterload increase).

RESULTS: Arterial oxygen content, diastolic pressure, and coronary perfusion pressure declined after creation of single-ventricle physiology (P < .05). Acute single-ventricle physiology resulted in higher myocardial blood flow (P < .05), unchanged subendocardial/subepicardial flow ratio and oxygen delivery, and lower coronary resistance (P < .01) as compared with biventricular physiology. Afterload augmentation increased coronary perfusion pressure, causing a trend for higher myocardial blood flow and oxygen delivery (P = NS), without affecting subendocardial/subepicardial flow distribution. Myocardial oxygen supply/demand balance fell in single-ventricle physiology, remaining unchanged during afterload augmentation.

CONCLUSIONS: Our study demonstrates that, in acute single-ventricle physiology with aortopulmonary shunt, myocardial blood flow is maintained by lower coronary perfusion pressure. Further, single-ventricle physiology results in less favorable myocardial oxygen supply/demand balance, although normal transmural myocardial blood flow distribution is maintained. Avoidance of diastolic runoff (ventricle-pulmonary conduit) could improve coronary reserve. In our study, moderate afterload augmentation did not induce relative subendocardial malperfusion, nor did it worsen oxygen supply/demand balance.

Abbreviations and Acronyms CaO 2 = arterial oxygen content; CPP = coronary perfusion pressure; LV = left ventricle/ventricular; MBF = myocardial blood flow; NS = not significant; RPP = rate-pressure product; SVP = single ventricle physiology; SVR = systemic vascular resistance






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