Coronary Artery Bypass Grafting: Historical Context
The advent of selective coronary angiography in 1958 by Sones and Shirey quickly established coronary anatomy as the basis for defining surgical revascularization:[1] both the indications in patients with ischemic heart disease and the technical principles of the procedure. Based on the pioneering work of Vineberg,[2] Olearchyk,[3] Sabiston,[4] Garrett et al.,[5] Favaloro,[6] Johnson et al.,[7] Green et al.[8] and others, there evolved a relatively safe and effective procedure of direct myocardial revascularization to treat patients with insufficient blood flow to the heart owing to blockages in the epicardial coronary arteries, identified by this new technology of coronary angiography. Beginning in 1967, the Cleveland Clinic group performed 1086 coronary artery bypass grafting (CABG) procedures in 951 patients, with an overall mortality of 4.2% by June 1970.[9]
Interestingly, this experience is remarkable considering how much the development of direct myocardial revascularization was driven by factors beyond anatomy alone, including an understanding of the physiology of blood flow, acute thrombosis (of left main patch repairs), the physiology of arterial grafts versus vein grafts and the importance of collateral flow from other regions of the myocardium.
The conceptual and practical basis of revascularization with CABG has been the underlying coronary anatomy, grafting beyond the atherosclerotic stenotic plaque and/or thrombotic occlusion of the target vessel epicardial coronary artery (TVECA). The indications for surgical intervention were based on this anatomy in two ways. Gould et al. arbitrarily correlated the percentage of anatomic stenosis with reduction in blood flow,[10,11] while the CASS trial spurred evolution of this anatomic construct into left main disease (>50% obstruction at angiography) and one-, two- and three-vessel disease (either >50 or >70% stenoses at angiography).[12] Depending upon the anatomic extent of stenoses in major TVECAs, limitations in regional blood flow and perfusion were assumed in the anterior (left anterior descending [LAD] coronary artery), lateral (circumflex coronary artery) and inferior (right coronary artery in patients with a right-dominant anatomy, the distal circumflex in patients with a left-dominant anatomy) areas of the myocardium. Frequently, in addition to these TVECAs, branches also have anatomic stenoses suitable for bypass grafting by anatomic criteria. Early on, the principle of complete anatomic revascularization became linked to these anatomic stenotic triggers, because incomplete revascularization based on this anatomy-derived construct for revascularization was associated with a 15% reduction in 5-year survival.[13]
More recently, advances in our understanding of stable ischemic heart disease (SIHD) and the importance of functionality in percutaneous revascularization have begun to challenge this anatomic construct in revascularization, including CABG surgery. Interestingly, this challenge brings us back full circle to the physiology of myocardial blood flow, perfusion and the relief of ischemia through CABG. While there are many other factors that influence patient-level decision-making in revascularization, such as comorbidities, the presence of valve disease and the degree of impairment of left ventricular (LV) function, anatomy and now functional physiology remain the two principle frameworks for revascularization.
To be deliberately provocative, current important questions regarding surgical revascularization are proposed at the beginning of each major section of this perspective (Box 1). The discussion is intended to highlight the genesis of the questions and to give some insight into possible future answers.
Future Cardiol. 2014;10(1):63-79. © 2014 Future Medicine Ltd.
