PERSPECTIVE
NEJM
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The modern treatment of coronary artery disease began with the development of coronary bypass surgery more than three decades ago, which was followed by the development of coronary angioplasty more than two decades ago. Conventional bypass surgery offers patients excellent long-term revascularization, but it is a highly invasive procedure. By contrast, angioplasty offers minimally invasive revascularization whose effects are tempered by high rates of restenosis. In the past decade, both techniques have evolved, as attempts have been made to decrease the invasiveness of bypass surgery and to decrease the restenosis rate associated with angioplasty.
Currently available data, including the results of studies of long-term outcomes with coronary revascularization surgery, are for traditional bypass surgery performed through a sternotomy and using cardiopulmonary bypass and cardioplegia to provide a motionless surgical field. Anatomical issues such as the intramyocardial location or small diameter of coronary arteries do not preclude the use of this surgical approach. The visibility it affords decreases the risk of misidentification of branches of the coronary artery. In modern practice, except for those with major coexisting conditions, the hospital stay for patients undergoing traditional bypass surgery for triple-vessel disease has been reduced to approximately five days, and the hospital stay for single-vessel bypass surgery is now as short as three days. A standard has evolved for a long-term outcome that is considered by many to be a benchmark for analysis of outcomes after treatment of coronary artery disease � traditional bypass surgery in which the left internal thoracic artery is used. Left-internal-thoracic-artery grafts used in the anterior descending coronary artery have patency rates of more than 90 percent at 15 years. Thus, any study comparing long-term outcomes of different treatments for coronary artery disease should also use the outcome standard for traditional coronary artery surgery.
The term "minimally invasive" has been used to describe bypass surgery performed through a smaller incision, bypass surgery performed on the beating heart without the use of cardiopulmonary bypass, or both, as in the report by Diegeler et al. in this issue of the Journal (see pages 561�566). Although a shorter incision may be appealing, the benefit is lost if it compromises the revascularization; indeed, studies have suggested that bypass surgery performed through a small incision may be associated with lower patency rates than bypass performed through a sternotomy. Furthermore, the length of the incision does not correlate with the morbidity or mortality associated with the procedure or with the efficacy of the operation.
Because of the potential complications of cardiopulmonary bypass (including neurocognitive impairment), surgeons are evolving techniques to perform bypass surgery � even multiple bypasses � on the beating heart without cardiopulmonary bypass. Avoidance of cardiopulmonary bypass and aortic manipulation (a potential source of embolic debris) may prove to cause fewer complications. Such a procedure can be performed through a sternotomy or through an incision offering minimal access (see Figure). However, randomized, prospective studies have not yet been conducted to determine whether this approach is superior to traditional coronary-artery bypass surgery. A critical test for newer surgical approaches is whether they produce the same long-term patency rates and survival advantage as traditional bypass grafting.
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After the introduction of angioplasty, it was recognized that there was a substantial rate of restenosis. Angiopathy also carries risks of complications and death, as Diegeler et al. confirm. Restenosis may occur for a variety of reasons. Some dilated arteries undergo elastic recoil because of fibrosis and calcification of the stenotic arterial segment that cannot be corrected by simple dilation. Dilation with stent implantation has remedied the problem of elastic recoil and reduced the incidence of restenosis. However, restenosis can still occur because of intimal hyperplasia within the stented arterial segment; this may be a particular risk for narrow coronary arteries requiring small-caliber stents. Recent studies using drug-coated stents suggest that these devices reduce the frequency of this important cause of recurrent stenosis, although long-term data are not yet available.
How should physicians choose between angioplasty with stent implantation and revascularization surgery, and how should they decide which approach to use? In some cases, the decision is made because of anatomical considerations � such as the location and type of lesion or the caliber of the artery � that increase the risks associated with angioplasty or the risk of restenosis. The age of the patient and the presence or absence of coexisting conditions that might decrease life expectancy or increase the risk associated with surgery should be considered. If surgery is elected, the choice of type of incision and the decision about whether to use or avoid cardiopulmonary bypass should take into account the patient's anatomy, the potential complications of the selected approach, and the potential risk of compromising the long-term patency of the graft. Because new options for and approaches to percutaneous intervention and surgery continue to evolve, both the interventional cardiologist and the cardiac surgeon should participate in the formulation of patients' treatment plans. In doing so, the clinicians involved should consider not only issues related to risks, but also those related to long-term patency and the survival of the patient.
Thomas E. MacGillivray, M.D.
Gus J. Vlahakes, M.D.
Massachusetts General Hospital
Boston, MA 02114