Aorta non-clamp technique in case of sclerotic ascending aorta during coronary artery bypass grafting

Abstract

We read with great interest the manuscript by Antunes MJ in which the author presented an open-anastomosis technique for proximal vein-graft anastomoses in case of sclerotic ascending aorta [1]. We present our comments on the paper from a few technical aspects. A similar technique has already been published by our group in 2006 [2]. We routinely prefer fibrillation without intermittent cross-clamping in the presence of calcification at the ascending aorta. Cardiopulmonary bypass is instituted by cannulation of right atrium and aortic arch, axillary artery, femoral artery or disease-free segment of ascending aorta depending on the extent of the atherosclerotic aortic disease [2]. We always institute a vent to prevent myocardial distension and permit unloading. A left ventricular vent through the right superior pulmonary vein, a pulmonary arterial vent or, sometimes, both may be inserted. A pulmonary arterial vent is safer and does not require special care of the perfusionist against air embolism when compared with a left ventricular vent [3]. We start with the distal anastomoses to the easily accessible coronary arteries as the cooling is started. At 29—30 8C, the heart usually fibrillates spontaneously; however, the patient is cooled down to 28 8C. The mean arterial pressure is kept 65 mm Hg until all the distal anastomoses are completed [2,3]. Additionally, following each distal anastomosis, heart is defibrillated, by which, we believe the conduction tissue replenishes the energy stores. Moreover, this measure is helpful to prevent bundle or branch blocks whichmay occur in the postoperative period [3]. Necessarily, consecutive anastomoses are performed with consequent fibrillation and defibrillation periods [2,3]. Before anastomosing the internal thoracic artery to the left anterior descending artery, we perform the proximal anastomoses. Proximal anastomoses are performed to the clean segments of the ascending aorta [1—3] if available on low flow with mean arterial pressure of 20—25 mm Hg, otherwise to the innominate or the internal thoracic artery [2,3]. We place ice bags around the head of the patient and the table is tilted to place the patient in the Trendelenburg position during low flow. Each proximal anastomosis lasts 3 min and, between each proximal anastomosis, flow is increased to normal. The bypass of the internal thoracic artery to left anterior descending artery is fashioned during re-warming to attenuate the hypothermic period. At the end of the bypass procedure, the heart is defibrillated if necessary [2,3]. Single or multiple clamping of the aorta during conventional cross-clamp cardioplegia and intermittent cross-clamp fibrillation techniques carries high risk of embolisation of the atheromatous material in the presence of a calcified ascending aorta [1—3]. The aorta non-clamp technique is a safer alternative in this particular group of patients. It may be performed on a fibrillating or decompressed beating heart [1]. However, we believe the institution of a vent is important for better myocardial protection.