Physiological and Metabolic Effects of Grafts in Coronary Artery Bypass Surgery

Abstract

Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp oronary artery bypass grafting (CABG) surgery initially utilizing a saphenous vein graft (SVG) and later the internal thoracic artery (ITA) has gained world-wide acceptance as a highly effective operation that not only ameliorates angina pectoris, but also improves both cardiac function and patient longevity. On the other hand, percutaneous coronary intervention (PCI) utilizing metallic or drug-eluting stents has also obtained rapid and world-wide popularity as a less invasive method of treating coronary artery obstructive disease, and many randomized clinical trials (RCT) are being conducted to compare the efficacy of CABG vs. PCI from the various clinical aspects of the different grades of illness. The endpoints of the trials include the occurrence of death, myocardial infarction, cerebral stroke and need for reintervention.I have long questioned why an ITA -left anterior descending artery (LAD) bypass can prolong a patient's life better than a SVG -LAD bypass, 1-3 why the use of bilateral ITAs can prolong life better than unilateral use, 4,5 and why CABG using the ITA can prolong life better than PCI in specific groups of patients, such as those with diabetes and elderly patients with triple-vessel disease, as has been demonstrated in the recent prospective RCT or retrospective risk-matched clinical studies. 6-9Furthermore, I have long considered that there are fundamental benefits of CABG with the use of ITAs, not only due to graft patency alone, but also due to differences in the endothelial metabolic effects of the ITA, SVG and coronary stents, particularly in patients with severe coronary endothelial dysfunction, such as multivessel coronary artery disease, 8 elderly patients 9 and diabetic patients. 6,7 Here, I review previous publications on these topics, while focusing on the physiological and metabolic function of the graft transplanted into the coronary artery systems by CABG surgery. Intraoperative Graft Flow and Postoperative Coronary Flow ReserveThe ITA graft flow is about 50-60% of the SVG flow when measured intraoperatively by electromagnetic flow meter 10 or a transit-time Doppler flow meter. 11 The limited flow of the ITA graft is attributed to its small luminal caliber and the length of the graft originating from the subclavian artery; both of which result in higher physiologic conduit resistance than with the SVG, which has a larger lumen and shorter length, usually originating from the ascending aorta. When CABG is performed under cardiopulmonary bypass and anoxic cardiac arrest, ITA malperfusion syndrome 12 occurs very rarely, which is when the ITA graft flow cannot meet the increased post-cardiac arrest hyperemic flow demand. In this setting, either a pharmacological or surgical addition is required to compensate for the hypoperfusion. Pharmacologically, an increase in the perfusion pressure and relief from coronary and/or graft spasm are necessary, and can be achieved with the administration...

Analysis of mortality in low-risk patients undergoing coronary artery bypass grafting : cardiovascular topic

“…LIMA–LAD bypass is the mainstay of coronary surgery 12,13. The LIMA is used extensively as a bypass graft, with excellent patency rates 13,14. However, careful technical preparation is needed to prevent occlusion.…”

Autologous microsurgical breast reconstruction and coronary artery bypass grafting: an anatomical study and clinical implications

“…In 2010, 64.2 CABGs were performed per 100,000 people in OECD countries, one in three of which were in women [18,35] (Table 1). Currently, the IMAs are the gold standard CABG conduits in terms of graft patency and patient survival [36][37][38] (see Table 3). Unlike other arterial conduits, the IMAs appear to be immune to atherosclerosis, vasospasm and endothelial injury [38][39][40].…”

Comparative genome-wide transcriptional analysis of human left and right internal mammary arteries

“…BIMAs display a significantly lower rate of atherosclerosis and, when used as grafts, seem to pass this protection to the native vessels; the rate of coronary disease progression after receiving an SVG is more than double that of LIMA grafts (48% versus 22%) [7,8]. This suggests that important factors contributing to the success of BIMA grafts may be the result of molecular differences among the tissues that are likely reflected in differences in gene expression.…”