Coronary Bypass Graft Surgery: Raising the Bar
August 1, 1998 4 minutes read
Coronary Bypass Graft Surgery: Raising the Bar
ABSTRACT & COMMENTARY
Synopsis: All arterial CABG procedure resulted in low mortality, morbidity, and reintervention over seven years. These results are superior to other reports of the results of vein grafts or vein grafts plus single or double ITA grafts in patients with three-vessel disease.
Sources: Peduzzi P, et al. Am J Cardiol 1998;81:1393-1399; Bergsma TM, et al. Circulation 1998;97:2402-2405.
The veterans administration cooperative study on coronary artery bypass graft (CABG) surgery vs. medical therapy for stable angina pectoris, which enrolled 686 patients between 1972 and 1974, was the first randomized trial of these two forms of therapy. This study established that left main coronary artery stenosis was best treated by surgery. In patients without left main obstruction, overall survival was not different between the medical and surgical groups for the first two years-possibly due to the high operative mortality at the time (5.8%). After two years, the surgical survival was better for the first decade but then dropped below the medical treatment group. The improved survival in the surgical group during the first decade was largely due to better survival of patients who had recurrent myocardial infarction (MI). After 5-10 years, the saphenous veins began to fail at a higher rate and disease proximal to the grafts became more common-necessitating repeat surgery at a higher mortality rate.
Peduzzi and associates now report on the 22-year follow-up of these patients. Among the 312 patients who underwent surgery, 25% eventually had reoperation, with an operative mortality of 10%. In the 354 medically treated patients, 160 (45%) eventually crossed over to surgery and 21% eventually had reoperation. Crossover to surgery and reoperation was not predictable based upon baseline clinical and angiographic characteristics. Cumulative survival over the 22 years was not different between the two groups (25% medical, 20% surgical; P = 0.24). However, a significant survival benefit for surgery was observed at 10 years but only in high-risk subsets. Low-risk patients, such as patients with one- or two-vessel disease or three-vessel disease with normal left ventricular function, had a better survival with medical therapy (31% vs 24%; P = 0.02). Because of the problem of perioperative MI (13% incidence with the first operation), the probability of remaining alive and free of MI was better with medical therapy (18% vs 11%; P = 0.003). Peduzzi et al conclude that saphenous vein coronary artery bypass surgery for stable angina patients does not decrease the incidence of MI and does not improve survival in low-risk patients. The surgical survival gain in high-risk patients lasts up to a decade and then deteriorates due to graft failure and need for reoperation.
Obviously, there have been improvements in surgical techniques since the mid 1970s. Operative mortality is now 1-2%, despite the fact that the mean age of patients undergoing surgery is increasing. Also, medical therapy has advanced with the addition of calcium blockers, ACE inhibitors, and aggressive lipid lowering. In addition, coronary interventions can delay the progression to multi-vessel disease. However, the most important advance may be the use of the arterial graft. Internal thoracic artery (ITA) grafts show a better long-term patency and could avoid the decline in surgical benefits seen after 10 years in the VA study. Thus, the report by Bergsma and associates from the University Hospital of Groningen in the Netherlands on the seven-year follow-up of patients with three-vessel disease who underwent total arterial graft surgery is of interest.
Over the last decade, Bergsma et al have been using both ITAs and the gastroepiploic artery in patients with three-vessel disease where feasible. They report on 256 patients, who represent 17% of their 3720 CABG patients over the five years ending in 1994. No patient was lost to follow-up, and the mean follow-up was 51 months. Total mortality was 4.7% (12 patients); four were perioperative deaths (1.6%). The seven-year actuarial survival was 91%. Perioperative MI occurred in five patients, and the seven-year MI-free survival was 97%. Subsequent angioplasty occurred in nine patients and reoperation in two; the seven-year freedom from intervention was 95%. Angina recurred following discharge in 28 patients; the angina-free survival at seven years was 85%. Bergsma et al conclude that the all arterial CABG procedure resulted in low mortality, morbidity, and reintervention over seven years. These results are superior to other reports of the results of vein grafts or vein grafts plus single or double ITA grafts in patients with three-vessel disease.
COMMENT BY MICHAEL H. CRAWFORD, MD
This is the longest follow-up to date of an all arterial graft approach using both ITAs and the gastroepiploic artery. However, as the VA study illustrates, a longer follow-up may be necessary to appreciate the potential advantages and disadvantages of this surgical approach. Also, this study has no medical control group, which would be of interest given the advances in medical therapy and interventional cardiology. In addition, we do not know the selection criteria for these patients. Were their patients all those with three-vessel disease who still had both ITAs or were other selection criteria used? We do know that 11% were reoperations and 4% had prior laparotomies. On the other hand, only 5% were diabetic. Until we understand how their patients were selected, we do not know if the results are applicable to the patients we encounter.
Despite these deficiencies in the study, it is highly interesting and suggests that, if the results hold up over a longer term, all arterial grafts with the gastroepiploic artery and the ITAs could become the surgical choice for three-vessel disease. These results bring up other issues. Does the all arterial approach mesh well with the trend toward minimally invasive CABG, or does this approach require better visibility? Is the gastroepiploic the best third conduit, or could other arteries be used? Are pedicle grafts better than free grafts, (i.e., radial artery)? Clearly, the bar is being raised for surgical approaches to coronary artery disease.
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