Coronary artery disease remains the most common pathology with which cardiologists and cardiac surgeons are faced. Accordingly, the practicing cardiac surgeon is confronted with no clinical question more often than, “Is coronary bypass indicated in this patient?” It is the aim of this chapter to provide a practical overview of the current indications for myocardial revascularization with sufficient reference to the relevant studies on which they are based to afford the reader an appreciation for the strengths and limitations of their conclusions.
A surgeon's first introduction to a patient with coronary artery disease is frequently an angiogram. In addition to the coronary anatomy, however, the clinical presentation and results of noninvasive studies of myocardial perfusion and function are necessary to characterize the pathophysiologic implications of the angiographic disease and its impact on prognosis and, therefore, to make a clinically appropriate recommendation. In the technological era in which we practice, the importance of the clinical history bears emphasis—particularly in an aging population. Because one of the objectives of surgery is to improve symptoms and quality of life, a thorough appreciation of the patient's functional status is a prerequisite in selecting the optimal therapeutic strategy.
The system proposed by the Canadian Cardiovascular Society for grading the clinical severity of angina pectoris is widely accepted (Table 19-1). Unfortunately, angina is a highly subjective phenomenon for both patient and physician, and prospective evaluation of the assessment of functional classification by the CCS criteria has demonstrated a reproducibility of only 73%.1 Furthermore, there may be a strikingly poor correlation between the severity of symptoms and the magnitude of ischemia, as is notoriously the case among diabetic patients with asymptomatic “silent ischemia.”
Table 19-1 Canadian Cardiovascular Society Angina Classification ||Download (.pdf)
Table 19-1 Canadian Cardiovascular Society Angina Classification
|Canadian Cardiovascular Society|
|0 = No angina|
|1 = Angina only with strenuous or prolonged exertion|
|2 = Angina with walking at a rapid pace on the level, on a grade, or upstairs (slight limitation of normal activities)|
|3 = Angina with walking at a normal pace less than 2 blocks or one flight of stairs (marked limitation)|
|4 = Angina with even mild activity|
Electrocardiography (ECG), if abnormal, is helpful in assessing ischemic burden. Unfortunately, it demonstrates no pathognomonic signs in half of patients with chronic stable angina. Still the monitoring of an ECG under stress conditions is simple and inexpensive, and is therefore useful as a screening examination. Among patients with anatomically defined disease, stress ECG provides additional information about the severity of ischemia and the prognosis of the disease. The sensitivity of the test increases with age, with the severity of the patient's disease, and with the magnitude of observed ST-segment shift.2 If ST- segment depression is greater than 1 mm, stress ECG has a predictive value of 90%, whereas a 2-mm shift with accompanying angina is ...