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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 (CAD) 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 for 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 for perioperative complications does not justify widespread cardiac testing among all groups of surgical patients.
Among patients undergoing vascular surgery, however, the perioperative risk for 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. CAD remains the major cause of death after any vascular operation ; therefore consideration for preoperative coronary artery revascularization is 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 for associated CAD, and the functional capacity of the patient ( Fig. 4.1 ). Determining the probability that a patient has severe obstructive CAD 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 for 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, , which 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 diabetes), 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 3 gallop, 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 (metabolic equivalent of task) demand, a level compatible with routine daily activities, there is increased risk for 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 CAD or left main disease is considered high risk and is associated with an increased risk for 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 CAD 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 CAD is an identifier of long-term survival after vascular surgery ( Fig. 4.2 ). 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 CAD should be an essential part of preoperative management. The paucity of prospective randomized data, however, has made it difficult for physicians to reach a consensus on the optimal strategy for those patients with CAD 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 CAD 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, 0.70–1.37). 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 CAD undergoing noncardiac surgery ( Table 4.1 ). ,
TABLE 4.1
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 |
CARP, Coronary Artery Revascularization Prophylaxis; DECREASE, Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography.
Landesberg and colleagues have accumulated enormous experience over the past decade and have shown that preoperative stress imaging tests with thallium can identify patients with a worse postoperative outcome. They have also shown the utility of a clinical scoring system that, in conjunction with a high-risk preoperative thallium test, suggests improved outcomes with preoperative coronary artery revascularization. The authors have implied that the CARP results are not generalizable because the trial was underpowered for high-risk coronary anatomy because of the low prevalence of patients with triple-vessel CAD and the exclusion of unprotected left main stenoses from randomization. To address this potential limitation, however, Poldermans and colleagues tested the benefit of a strategy of preoperative coronary artery revascularization in patients with high-risk stress imaging test results who were scheduled for vascular surgery. Their preliminary results showed a borderline unfavorable outcome with revascularization 1 year after vascular surgery (mortality rate at 1 year: revascularization, 26.5%; no revascularization, 23.1%; p = 0.58). In a subgroup analysis of the CARP trial, we found no evidence of clinical benefit among patients with multivessel CAD randomly assigned to prophylactic revascularization. Monaco and colleagues randomly assigned 208 high-risk patients undergoing vascular surgery to a “selective strategy” consisting of coronary angiography based on high-risk findings on noninvasive imaging or a “systematic strategy” that consisted of routine preoperative coronary angiography with coronary revascularization as needed. As expected, the revascularization rate was higher in the systematic strategy arm of the study (58% versus 40%). Although in-hospital cardiac complications were similar in the two groups, a reduction in major cardiac events (MACE), including mortality, was reported during long-term follow-up in favor of a systematic strategy (86% versus 69%). The authors presumed this was because of higher utilization rates of coronary revascularization in the systematic strategy arm.
So how should a clinician integrate the findings from these three studies into a unified approach in the preoperative period? Although the findings from Landesberg and colleagues are informative for prognosis, the potential selection bias that favors any decision to undergo coronary artery revascularization in some patients is an important limitation on predicting late outcomes on retrospective analyses. Likewise, in the study by Monaco and colleagues, the decision to perform coronary revascularization was not randomized, and this could explain the disproportionate magnitude of the benefit (20% absolute and 50% relative risk reduction in MACE at 8 years) with only modest differences in utilization rates of coronary revascularization.
The study results of the DECREASE (Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echo)-V pilot study and the CARP trial do not support an aggressive strategy in the vast majority of patients with stable cardiac symptoms. One important exception to this general rule is worth mentioning. Patients with left main CAD were excluded from the randomization process in CARP, but their management and outcomes after vascular surgery were captured in the CARP registry. This subset of patients consisted of 48 of 1048 patients undergoing preoperative coronary angiography before their intended vascular surgery (4.6%). Although their long-term survival rate appears to be improved with preoperative coronary artery revascularization (survival at 2.5 years for surgically and medically treated left main disease was 84% and 52%, respectively; p < 0.01), it is uncertain that the prevalence of such a small cohort before vascular surgery warrants widespread screening with expensive stress imaging tests.
OTHER INTERVENTIONS
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