Should Patients with Stable Coronary Artery Disease Undergo Prophylactic Revascularization before Noncardiac Surgery?

Introduction

The preoperative assessment of a patient in need of elective noncardiac surgery is often a difficult task. There has been enormous controversy regarding the appropriate strategy for diagnosing and managing coronary artery disease before elective noncardiac surgery because of the paucity of clinical trial data. Overall, elective surgical procedures in a population of general medical patients are associated with a very low risk of perioperative cardiac complications; the incidence of either myocardial infarction (MI) or death is less than 1%. Although the risk increases with the age of the patient, the low risk of perioperative complications does not justify widespread cardiac testing among all groups of surgical patients.

Among patients undergoing vascular surgery, however, the perioperative risk of cardiac complications is high. Although the reasons relate, in part, to the hemodynamic stresses associated with aortic procedures, the prevalence of atherosclerotic heart disease in patients undergoing vascular surgery exceeds 50% and therefore may require special attention in the preoperative period. Coronary artery disease remains the major cause of death after any vascular operation ; therefore consideration for preoperative coronary artery revascularization has been a justifiable endeavor.

Options

As outlined by the American College of Cardiology/American Heart Association (ACC/AHA) Task Force recommendations before noncardiac operations, the approach to assessing the potential cardiac risk associated with any patient scheduled for an elective noncardiac operation includes the nature of the operation, the risk of associated coronary artery disease, and the functional capacity of the patient ( Figure 11-1 ). Determining the probability that a patient has severe obstructive coronary artery disease is one key ingredient of the preoperative risk assessment and should be based initially on the clinical history coupled with the nature of the operation. This entails the understanding that patients with vascular and orthopedic operations have the highest risk of postoperative cardiac complications compared with other noncardiac operations. Specifically, individuals in need of a vascular operation involving an abdominal approach for either an expanding abdominal aortic aneurysm or advanced claudication have the highest risk. Although urgent and emergent vascular operations occur in at least 20% of screened patients undergoing vascular operations, these individuals are rarely considered candidates for preoperative coronary angiography and their preoperative risk management will not be addressed. The initial evaluation requires an assessment of a prior history of cardiac problems or risk factors along with either classic angina or unusual symptoms such as shortness of breath or atypical chest pains. Attention should be given to clinical risk variables and include age greater than 70 years, angina, history of congestive heart failure, prior MI, prior stroke or transient ischemic attack (TIA), history of ventricular arrhythmias, diabetes mellitus (particularly insulin dependent), and abnormal renal function (creatinine level greater than 2.0 mg/dL). The physical examination also provides insight into high-risk variables, including a chronic debilitated state, increased jugular venous distention, edema, S ₃gallop, and significant aortic stenosis, and the 12-lead electrocardiogram (ECG) provides prognostic information related to the presence of abnormal Q waves or heart rhythms. Although select clinical variables do predict perioperative cardiac morbidity and mortality risk, the optimal risk stratification tool for prediction of all complications in the postoperative period is controversial. The final approach, therefore, is to determine whether, despite the absence of unstable clinical variables, there is sufficient concern to justify provocative stress testing preoperatively. Assessing the functional capacity of patients undergoing elective operations is an important ingredient in determining whether a patient can withstand the rigors of a prolonged operation. In those patients who are unable to achieve a 4-MET demand, a level compatible with routine daily activities, there is increased risk of postoperative events, and additional testing may be warranted. Among patients with sufficient exercise capacity and an interpretable ECG, stress testing with an ECG alone may be a cost-effective means of risk stratification for low-risk patients who do not need additional cardiac workup. Among those patients who cannot exercise or who have baseline ECG abnormalities, stress imaging tests have been recommended as the standard alternative for the preoperative detection of multivessel coronary artery disease. The presence of multiple ischemic segments indicative of either multivessel coronary artery disease or left main disease is considered high risk and is associated with an increased risk of perioperative cardiac complications and reduced long-term survival. Ultimately, a combined approach of using clinical variables associated with stress imaging tests is most cost-effective. The role of adjuvant pharmacologic therapies cannot be overemphasized and will be addressed in other chapters.

Evidence

Role of Coronary Revascularization

Severe coronary artery disease is common among patients undergoing vascular surgery and is a major determinant of long-term survival after vascular surgery. Thus the role of coronary revascularization in the preoperative management of patients with stable coronary artery disease has been one of the most debated issues in the field of perioperative medicine. As part of the Coronary Artery Revascularization Prophylaxis (CARP) trial, we have learned from the registry and randomized cohorts undergoing preoperative coronary angiography that the extent and severity of coronary artery disease is an identifier of long-term survival after vascular surgery ( Figure 11-2 ). This observation, coupled with outcome data from the Coronary Artery Surgery Study (CASS), which suggested better outcomes in patients with vascular disease who underwent coronary artery bypass surgery, would support a plausible hypothesis that widespread identification and treatment of coronary artery disease should be an essential part of preoperative management. The paucity of prospective randomized data, however, made it difficult for physicians to reach a consensus on the optimal strategy for those patients with coronary artery disease who are scheduled for elective noncardiac surgery. A survey conducted before the publication of the CARP trial showed that recommendations for preoperative revascularization deviated from the guidelines 40% of the time, and the chance of widely disparate opinions among the participating cardiologists was 26%. Clearly, a large-scale trial was needed to test the long-term benefit of preoperative coronary artery revascularization before major noncardiac operations.

The CARP trial was the first randomized, multicenter study designed to assess the role of prophylactic revascularization in patients with coronary artery disease undergoing elective vascular operations. Over a 4-year period involving 18 university-affiliated Veterans Affairs medical centers, 510 (9%) of 5859 screened patients were enrolled and randomly assigned to a preoperative strategy of either coronary artery revascularization or no revascularization before elective vascular surgery. The surgical indications were an abdominal aortic aneurysm in 169 (33%) or symptoms of lower extremity arterial occlusive disease including severe claudication in 189 (37%) and rest pain in 152 (30%). Among the patients randomly assigned to a strategy of preoperative coronary artery revascularization, percutaneous coronary intervention (PCI) was performed in 141 (59%) and bypass surgery was performed in 99 (41%). The results of the study showed that procedural-related deaths associated with coronary artery revascularization occurred in only 1.7% of the patients, and no complications were related to cerebrovascular events, loss of limbs, or dialysis. The median times (interquartiles) from randomization to vascular surgery were 54 (28, 80) days in the coronary revascularization group, however, and 18 (7, 42) days in the no-revascularization group ( p < 0.001). Within 30 days after vascular surgery, the mortality rate was 3.1% in the coronary revascularization group and 3.4% in the no-revascularization group ( p = 0.87). An MI, defined by any elevation in troponins after vascular surgery, occurred in 11.6% of the revascularization group and in 14.3% of the no-revascularization group ( p = 0.37). At a median time of 2.7 years after randomization, the mortality rates were 22% in the revascularization group and 23% in the no-revascularization group ( p = 0.92; relative risk, 0.98; 95% confidence interval, 0.70 to 1.37). The conclusions from the CARP study are that, among patients undergoing elective vascular surgery, a strategy of preoperative coronary artery revascularization before elective vascular surgery does not improve outcome but rather may delay or even prevent the needed vascular procedure. Based on these data, coronary artery revascularization before elective vascular surgery among patients with stable ischemic heart disease is not supported. Since the CARP trial was published, three other studies have reported outcomes in patients with coronary artery disease undergoing noncardiac surgery ( Table 11-1 ).

TABLE 11-1

Clinical Studies Assessing the Role of Coronary Revascularization before Major Vascular Surgery

	CARP Trial	DECREASE-V Pilot	Landesberg Study	Monaco Study
Study design	Multicenter, prospective	Multicenter, prospective	Single center, retrospective	Multicenter, prospective
Treatment allocation	Randomized	Randomized	Nonrandomized	Randomized
Endpoint	Mortality rate at 2.7 yr	Mortality rate at 1 yr	Mortality rate at 3 yr	Major adverse cardiac events
Treatment effect	No benefit	No benefit, possible harm	Benefit in intermediate risk	Benefit
Total patients screened	5859	1880	624	672
Total patients randomized	510	101	N/A	208
Patients with three-vessel or left main disease	93	37	73	55
Mortality rate: no revascularization group	23%	23.1%	21.8%	Not reported
Mortality rate: revascularization group	22%	26.5%	14.6%	Not reported