Revascularization procedures for patients with Angina Pectoris

Indications

The indications for coronary artery revascularization in patients with angina pectoris are often debated. There is general agreement that otherwise healthy patients in the following groups should undergo revascularization: (1) patients with unacceptable symptoms despite medical therapy to its tolerable limits, (2) patients with left main coronary artery stenosis greater than 50% with or without symptoms, (3) patients with three-vessel disease with left ventricular dysfunction (ejection fraction < 50% or previous transmural infarction), (4) patients with unstable angina who after symptom control by medical therapy continue to exhibit ischemia on exercise testing or monitoring, and (5) post-myocardial infarction patients with continuing angina or severe ischemia on noninvasive testing. (See sections on Unstable Angina and Myocardial Infarction.)

In addition, many cardiologists feel that patients with less severe symptoms should be revascularized if they have two-vessel disease associated with underlying left ventricular dysfunction, anatomically critical lesions (> 90% proximal stenoses, especially of the proximal left anterior descending artery), or physiologic evidence of severe ischemia (early positive exercise tests, large exercise-induced thallium scintigraphic defects, or frequent episodes of ischemia on ambulatory monitoring).

This trend toward aggressive intervention has accelerated as a result of the growing use of coronary angioplasty and stenting. While such patients are at increased risk, it has not been proved that their prognosis is better after coronary revascularization by either surgery or angioplasty.

Type of Procedure

A. Coronary Artery Bypass Grafting (CABG)
CABG can be accomplished with a very low mortality rate (1-3%) in otherwise healthy patients with preserved cardiac function. However, the mortality rate of this procedure rises to 4-8% in older individuals and in patients who have had a prior CABG. Increasingly, younger individuals with focal lesions of one or several vessels are undergoing coronary angioplasty as the initial revascularization procedure.

Grafts employing one or both internal mammary arteries (usually to the left anterior descending artery or its branches) provide the best long-term results in terms of patency and flow. Segments of the saphenous vein (or, less optimally, other veins) or the radial artery interposed between the aorta and the coronary arteries distal to the obstructions are also utilized. One to five distal anastomoses are commonly performed. After successful surgery, symptoms generally abate. The need for antianginal medications diminishes, and left ventricular function may improve.

Minimally invasive surgical techniques utilize different approaches to the heart than standard sternotomy and cardiopulmonary bypass. The surgical approach may involve a limited sternotomy, lateral thoracotomy (MIDCAB), or thoracoscopy (port-access). These approaches may be used in conjunction with standard cardiopulmonary bypass, with peripheral cardiopulmonary bypass, or with operating on the beating heart utilizing a mechanical coronary stabilizer. Avoiding bypass may lessen the risk of cerebral complications. These techniques allow earlier postoperative mobilization and discharge. They are more technically demanding, usually not suitable for more than two grafts, and do not have established durability.