Influence of Ascending Versus Descending Balloon Counterpulsation on Bypass Graft Blood Flow

Background. Mechanical circulatory assistance is frequently needed in postcardiotomy patients to support the failing heart. A balloon catheter called SupraCor (ABIOMED Cardiovascular, Inc, Danvers, MA) has been developed and is similar to the existing intraaortic balloon pump with the exception of placement in the ascending versus the descending thoracic aorta. This investigation compared the effects of SupraCor versus standard intraaortic balloon pump on internal mammary artery and venous conduit bypass graft blood flow. Methods. Porcine total heart bypass was used to anastomose a jugular vein from the ascending aorta to a subsequently ligated left anterior descending coronary artery. The left internal mammary artery was then anastomosed to the jugular vein so each conduit perfused the same coronary vascular bed. An additional right heart bypass preparation allowed precise control of cardiac output and blood pressure, which were maintained constant throughout mechanical circulatory assistance. Electromagnetic flow probes measured flow through each bypass graft and the other conduit was atraumatically occluded. Results. The SupraCor caused a significant increase in both internal mammary artery (+70% from 35 ± mL/min to 56 ± 9 mL/min; p = 0.04) and venous bypass graft blood flow (+49% from 66 ± 12 mL/min to 95 ± 15 mL/min; p = 0.02) when compared with controls. The intraaortic balloon pump failed to alter internal mammary artery or venous bypass graft flow. Conclusions. The results demonstrate that counterpulsation with an ascending aortic balloon significantly increases coronary bypass graft flow in both internal mammary artery and venous conduits. In contrast, counterpulsation with a descending aortic balloon did not alter coronary bypass graft flow.