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Minneapolis, MN
Minneapolis, MN
Dr. Ward is Professor of Surgery and Dr. Kelly is Assistant Professor of Surgery, University of Minnesota.
Correspondence to: Herbert B. Ward, MD, PhD, Cardiothoracic Surgery (112), VA Medical Center, One Veterans Dr, Minneapolis, MN 55417; e-mail: wardx020{at}umn.edu
A surgeon’s decision to perform myocardial revascularization using conventional techniques (ie, coronary artery bypass grafting [CABG]) on cardiopulmonary bypass (CPB) or to use newer techniques without the aid of CPB (ie, off-pump coronary artery bypass [OPCAB]) has been influenced by many factors. CPB is known to cause a complex of systemic inflammatory responses and has been associated with several adverse postoperative outcomes, including renal, pulmonary, neurologic, and coagulopathic complications and even end organ dysfunction.1 Surgeons driven to reduce both the short-term and long-term morbidity associated with CPB find OPCAB to be an attractive alternative.
First performed in the early 1960s simply because the CPB technology did not yet exist, OPCAB has experienced a resurgence of interest as a potential solution to the vexing problems associated with the use of CPB.2 The excellent outcomes obtained with CABG mandate that studies be done to confirm that OPCAB provides a statistically significant improvement. The subtle effects of CPB such as mild memory loss or confusion are hard to quantify, making it difficult to demonstrate a clear advantage of one technique over the other.3 Conversely, gross effects such as blood loss or transfusion requirements can be assessed accurately but may be of less importance when compared to the completeness of revascularization or graft patency.4 Nevertheless, studies have compared CABG to OPCAB focusing on important parameters of outcome (ie, mortality, stroke, graft patency, completeness of revascularization, and renal dysfunction) and total cost (ie, length of stay, cost of materials, time to extubation, and time in the ICU).
Important questions need to be asked by surgeons when choosing which operation to perform. Should the experience of the operative surgeon determine whether to use OPCAB or CABG? When should surgeons potentially sacrifice graft patency or safety to justify learning a new, but potentially better, technique? When and how often should graft patency be intraoperatively assessed in patients undergoing myocardial revascularization? Should the experience of the operative surgeon be considered when deciding to confirm graft patency? In teaching institutions, should CABG techniques be taught before or simultaneously with OPCAB techniques?
There are several prospectively randomized trials and a recently published meta-analysis, either in progress or recently completed, that attempt to definitively answer some of these questions. Parolari et al5 performed a meta-analysis of all randomized trials of OPCAB vs CABG from 1990 to 2002. They found nine comparable trials (peer reviewed, prospective, and randomized) with a total of 1,090 patients (CABG, 558 patients; OPCAB, 532 patients). Using a composite end point of death, stroke, or myocardial infarction, there was a trend toward reduction in risk (odds ratio, 0.48; p = 0.08) in patients in the OPCAB groups but no clear benefit. Most of the studies were from Europe, and four of the studies had the same author. Another carefully performed and statistically robust study6 comparing OPCAB with CABG also suggested improved clinical outcomes with OPCAB. In particular, this conclusion may apply to important subgroups of patients (eg, octogenarians).7 Other studies3 8 9 have found no difference in outcomes referable to the technique chosen, and one article10 simply concluded by saying that patients undergoing OPCAB are not exposed to a greater risk of short-term adverse outcomes.
A well-done but only partially published manuscript (the graft patency data were not included and will not be published until the 1-year angiograms are completed) by Puskas et al4 has demonstrated that a single experienced surgeon who is well-versed in OPCAB and CABG techniques can have improved results without CPB. With similar patient characteristics, unselected prospectively randomized patients receiving OPCAB had the same following results: number of grafts; number of grafts to the lateral wall; number of arterial grafts; rates of death, atrial fibrillation, and stroke; and rate of hospital readmission when compared to CABG patients. OPCAB patients also had less blood loss, fewer blood transfusions, shorter time to extubation, less myocardial injury (ie, lower myocardial serum enzyme levels), and shorter length of hospital stay than CABG patients. This pattern has been confirmed by other recent publications.6 7 11
Of interest is an ongoing multi-institution randomized trial in the Veterans Affairs Cooperative Studies Program (CSP 517) that will not only compare graft patency and completeness of revascularization between OPCAB and CABG, but also will carefully assess neuropsychological outcomes and the effect of the experience of the operative surgeon. A total of 2,200 patients requiring surgical myocardial revascularization only will be prospectively randomized over a 4-year accrual period. The short-term primary end point will be a composite of death, repeat surgery, cardiac arrest, stroke, and/or renal failure. The long-term primary end point will be a composite of death, myocardial infarction, and/or repeat revascularization. It is hoped that the results of such a large prospective trial will resolve some of the dilemmas faced by cardiovascular surgeons as to the best operation for a particular patient.
Meanwhile, efforts by surgeons who are well-versed in OPCAB techniques, such as those described in the article by Reuthebuch et al12 in the February issue of CHEST, are attempting to improve the results of OPCAB. A particularly important concern in OPCAB is graft patency and anastomotic stenosis (ie, complications that could be corrected during the same operation). Reuthebuch et al have combined their talents with the technologic innovations of Novadaq Technologies to provide surgeons with a relatively simple, safe, and time-efficient way to assess graft patency during OPCAB. OPCAB requires a steep learning curve, and the technology described will help to ensure that OPCAB provides safe, reproducible, and complete myocardial revascularization.
In conclusion, it appears that OPCAB techniques offer some advantages over CABG and that a continuation of this approach is justified. The fact that only 18% of surgical myocardial revascularization operations are performed with OPCAB techniques suggests that OPCAB has not been universally accepted.4 In the hands of experienced and committed surgeons using appropriate patient selection, OPCAB surgery may result in improved outcomes. However, OPCAB techniques should never be chosen for such inappropriate reasons as cost alone, marketing, or machismo. Lack of a commitment to truly learning and understanding OPCAB surgery undoubtedly will lead to mediocre outcomes and limited utilization of a promising technology.
References
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