Complete revascularization on cardiopulmonary bypass: a closer look at existing technology*1

During the 1990s, two significant advancements altered the thinking on the surgical treatment of coronary artery disease. The first is the documentation that complete arterial revascularization further improves patients survival, increases the symptom free interval and decreases the incidence of reoperation as compared to saphenous vein grafting with and without left internal mammary artery grafting [1–5]. This concept is an evolution in the ongoing development of the treatment of ischemic heart disease. Moreover, life span is prolonged by coronary interventional therapy only if the internal mammary artery bypass to the anterior descending coronary artery is performed [6]. When coupled with completeness of revascularization utilizing arterial conduits, including the radial artery, gastroepiploic artery and one or two mammary arteries, further longevity can be predicted [4]. Arterial conduits are of consistent quality whereas saphenous veins are variable. Saphenous vein diameter, wall thickness and status of the valves differ among patients. In females and the elderly, veins may be fragile or may contain significant disease such that they become substantively inert conduits. In patients with severe varicose veins, early occlusion can be expected. Predictors of the development of vein graft disease are not well delineated. Other venous conduits, including the cephalic vein, have demonstrated poor long-term patency. Decision making regarding the choice of conduit influences the conduct of the operation proposed for the patient. Secondly, but not less important, is the development of minimally invasive cardiac surgery. This approach represents a revolution rather than an evolution. As opposed to having one operation for all individuals, regardless of the presence of confounding co-morbid risk factors, minimally invasive coronary artery surgery has offered alternative approaches to the treatment of selective (minimally invasive direct coronary artery bypass, MIDCAB) or complete (off-pump coronary bypass, OPCAB) revascularization in patients who have significant risk factors for the use of cardiopulmonary bypass (CPB) and facilitates recovery in patients without such risk [7,8]. In this way, operative procedures are designed for the patient rather than the patient for the operation. Evidence is compiling that coronary artery surgery without the use of CPB is safe and effective and graft patency can be compared over the short term to procedures done on CPB [9]. Data would also indicate similar intermediate term results [7]. There is conflicting data regarding early recurrence of lesions particularly at arterial snare sites that may abrogate such thinking [10]. Others argue cogently, that in a modern coronary surgical practice, operating on the beating heart via small incisions is inappropriate except in a few select patients [11,12]. The question arises just because minimally invasive coronary bypass surgery exists can it or should it be used for all procedures? How does aforementioned information interact with the choice of operative procedure? Certainly, complete coronary bypass surgery can be successfully performed without the use of CPB in many if not most patients via sternotomy or thoracotomy [7,8,13]. The use of stabilization equipment has improved the graft patency in beating heart surgery [8]. Mack et al. [9] demonstrated a 97% patency of arterial anastomoses to the left anterior descending artery (LAD) performed via left thoracotomy without the use of CPB. Such data has not been demonstrated for arterial conduits elsewhere on the heart. Realistically, access to the posterior, posterolateral, and inferior surfaces of the active heart utilizing the existing stabilizing equipment is not as adequate or satisfactory as that of the anterior descending system. The complete arterial revascularization sequences proposed by Tector [2] and by Barner [4] with the use of multiple arterial anastomosis requires precision and the use of fine surgical suturing techniques may not be feasible on the beating heart. Further, because of the limitation of arterial conduit to accomplish completeness in revascularization, sequential bypass grafting using composite mammary arteries or the radial artery to the posterior cardiac wall may be necessary [2,4]. Adequate exposure and suturing of such conduits on the beating heart is not as precise given the fragile arterial walls and the relatively crude stabilization systems currently available. There are many benefits to traditional coronary artery bypass surgery (Table 1), which may override those of minimally invasive revascularization without CPB. The need for complete arterial revascularization can and occasionally must be sacrificed in patients with ascending aortic disease, in the elderly who are at risk for stroke, and in those with significant co-morbid risk factors, in order to provide symptomatic relief or even life saving surgical therapy where CPB may be contraindicated [14]. The occurrence of stroke is devastating. Even without mortality which approaches 20%, the long-term survival and quality of life in patients with major neurologic events is remarkably poor [15]. The impact on the family is also great. Certainly not using CPB can obviate the incidence of bypass induced cerebral events, but are there ways to make bypass more friendly rather than eliminating it entirely? This may be a goal for the future. The logarithmic development of technology to minimize surgical trauma may well allow precise complete arterial revascularization without the use of CPB. For the present, however, depending on the surgeon's experience and the vessels to be bypassed, complete arterial revascularization without the use of CPB may be fraught with technical difficulty resulting in incomplete surgical results and less than optimal outcomes for our patients. Prior to making the decision of which technique(s) to utilize, several questions (Table 2) need to be answered. Those answers, taken into account with surgical expertise and reliable clinical data, will indicate the conduct of operative procedure to match the unique anatomy and requirements of the individual patient, completing the procedure with the lowest morbidity, lowest mortality, most rapid return to activity and best long-term result possible. As in the appropriate delivery of all medical and surgical care, the thoughtful application of the risk/benefit ratio will determine the appropriate means of revascularization. Table 1. Benefits of operating on the still heart Table 2. Questions Presented at the 2nd MITSIG International Symposium: Controversies in Cardiothoracic Surgery, Hong Kong, November 20–21, 1998.