Ann Thorac Surg 2003;75:1152
© 2003 The Society of Thoracic Surgeons
Invited commentary
Brian Buxton, MD
Director of Cardiac Surgery, Austin and Repatriation Medical Centre, Level 5, Studley Road, Heidelberg, Victoria 3084, Australia
e-mail: brian.buxton{at}armc.org.au
Meticulous harvesting, pharmacologic dilatation, and avoidance of overdistention of a coronary artery bypass graft have been recognized as important steps during procurement, which may preserve graft function. Nonetheless, some vein grafts develop early complications such as thrombosis and neointimal hyperplasia which lead to atherosclerosis. Preservation during storage of a coronary artery graft between the time of harvest and implantation has received little attention, possibly because conduits are thought by many surgeons to be inert or robust and not particularly sensitive to hypoxic damage. Protection of the endothelium is of major importance in maintaining smooth muscle function and integrity. Vasodilatation is dependent on cytosolic Ca++ modulated by endothelial and nonendothelial dependent pathways such as nitric oxide cyclic guanosine monophosphate (NO-cGMP), prostacyclin and endothelium derived hyperpolarization. This paper demonstrates the importance of preserving vein grafts during storage to maintain structure and function, which the authors suggest may lead to improved patency.
Thatte and colleagues have explored an ingenious approach using near-infrared multiphoton microscopy in transmission and epifluorescent modes to assess the integrity of the human saphenous vein segments stored in different preservation solutions with the aim of designing more effective storage medium. Specific fluorescene stains were used to assess calcium and nitric oxide metabolism. Surprisingly, they demonstrated that using standard preservation solutions, calcium mobilization, and nitric oxide function diminished rapidly, and nearly all endothelial cells were nonviable after the first hour. In contrast, they discovered that veins can be stored up to 24 hours without substantial loss of viability or function using a newly formulated heparinized physiologic buffer solution (GALA) containing the antioxidant and reducing agents glutathione and ascorbic acid and L-arginine as a substrate for nitric oxide synthase.
Arterial grafts, which contain a high proportion of smooth muscle compared with saphenous veins may be even more prone to vasospasm from intimal and smooth muscle damage. In patients who had reoperation with a prolonged interval between the time of harvest and graft reimplantation, we have observed arterial grafts, which were dilated at the time of leaving the operating room, develop delayed vasoconstriction despite the use of systemic vasodilators. Storage in GALA solution following harvesting and vasodilatation is a logical development as demonstrated by this elegant research. GALA solution may protect the endothelium and the underlying smooth muscle in both arterial and venous grafts from ischemic damage and thus deserves clinical evaluation.
