REVIEW Preoperative Cardiac Risk Stratification 2007: Evolving Evidence, Evolving Strategies 1 Steven L. Cohn, MD, FACP Various guidelines and risk indices have optimized cardiac risk stratification, and 2 Andrew D. Auerbach, MD, MPH the emphasis has shifted to reducing perioperative risk. This review is an update on invasive (CABG/PCI) and noninvasive (medical therapy with beta-blockers, alpha- 1 State University of New York— Downstate, Divi- agonists, and statins) strategies to reduce cardiac risk for noncardiac surgery and sion of General Internal Medicine, Brooklyn, New the controversies surrounding their use. Journal of Hospital Medicine 2007;2: York 174–180. © 2007 Society of Hospital Medicine. 2 University of California San Francisco, Depart- ment of Medicine, San Francisco, California KEYWORDS: preoperative care, perioperative, risk assessment, beta-adrenergic blockers, percutaneous coronary intervention, coronary artery bypass, statin. ore than 33 million patients undergo surgery annually in the MUnited States. Approximately 8 million of these patients ei- ther have known coronary artery disease or risk factors for it, and an estimated 50,000 patients sustain a perioperative myocardial infarction, with an additional 1 million developing another med- ical complication. An integrated comprehensive approach is nec- essary to risk-stratify these patients in an attempt to reduce these complications. The basic role of risk stratification is to identify those patients at increased risk for complications; however, we are looking for a small number of patients at high risk in a population of relatively low-risk patients. Most surgical patients do well, and further di- agnostic testing has a low yield in predicting those likely to have a complication (poor positive predictive value [PPV]). Our goal should be to determine the underlying potential triggers of cardiac complications and institute measures to prevent them. After briefly reviewing pathophysiology, risk indices, and guidelines for preoperative cardiac risk assessment and diagnostic testing, we will focus on risk reduction strategies including prophylactic re- vascularization (CABG/PCI) and medical therapy. PATHOPHYSIOLOGY OF PERIOPERATIVE MYOCARDIAL INFARCTION Perioperative myocardial infarctions result from myocardial isch- emia or plaque rupture and coronary thrombosis.1 Myocardial ischemia may be caused by increased oxygen demand or de- creased oxygen delivery. Surgical trauma, anesthesia, pain, hypo- thermia, and bleeding trigger a stress state. This in turn increases catecholamine release, leading to tachycardia, hypertension, and increased oxygen demand. Anesthesia, hypotension, bleeding, Dr. Auerbach is supported by a K08 research and and anemia may produce hypoxia, with subsequently decreased training grant (K08 HS11416-02) from the Agency delivery of oxygen. Surgical trauma initiates an inflammatory re- for Healthcare Research and Quality. sponse, leading to plaque fissuring, and a hypercoagulable state, 174 © 2007 Society of Hospital Medicine DOI 10.1002/jhm.158 Published online in Wiley InterScience (www.interscience.wiley.com). which can result in acute coronary thrombosis. whether to test, it has been incorporated into a Perioperative prophylaxis should target these po- number of algorithms combining risk stratification tential triggers. with recommendations about noninvasive testing as well as use of perioperative beta-blockers.7–10 CARDIAC RISK INDICES AND GUIDELINES Over the past 3 decades, a number of cardiac risk DIAGNOSTIC CARDIAC TESTS indices have been published. The older group of Tests should not be done if the results will not alter indices was most notable for Goldman’s original patient management. If further assessment is indi- cardiac risk index2 and Detsky’s modification.3 The cated based on the ACC/AHA algorithm, other risk newer group consists of the American College of indices,10 or criteria independent of the need for Physicians (ACP) guidelines4 (now considered out- surgery, the physician must decide whether to do a dated), the American College of Cardiology/Ameri- noninvasive (eg, echocardiogram or stress test) or can Heart Association (ACC/AHA) guidelines (to be an invasive test (coronary angiography). Unless a pa- updated again in early 2007),5 and the Lee revised tient has independent criteria for angiography or, oc- cardiac risk index (RCRI).6 casionally, a very high prior probability of significant The 2002 ACC guidelines5 outline how to deter- CAD based on multiple risk factors, noninvasive test- mine the need for additional cardiac (usually non- ing is usually the preferred first step. A resting echo- invasive) testing (NIT): after ascertaining the ur- cardiogram is potentially useful for providing infor- gency of surgery, history of revascularization mation about suspected valvular heart disease but is procedures, and previous stress test results (if any), not a consistent predictor of ischemic events. a combination of clinical risk predictors, surgery- For ambulatory patients, exercise stress testing specific risk, and patient self-reported exercise ca- is usually preferred over pharmacologic testing; in pacity should be entered into an algorithm. The the perioperative setting, the usefulness of exercise guidelines state a shortcut can be used: noninvasive testing is limited by the indications for obtaining testing should be considered if a patient has any 2 stress testing (namely, poor functional status) as of the following: (1) intermediate clinical risk (sta- well as its main limitation, patient inability to reach ble angina or old MI, compensated heart failure, 85% of the target heart rate. As a result, pharmaco- diabetes mellitus, renal insufficiency), (2) high-risk logic stress testing should be the primary modality surgery (aortic or major vascular procedures, pro- for patients requiring preoperative risk stratifica- longed surgery with significant expected blood loss tion. Pharmacologic stress testing can be done with or fluid shifts), or (3) poor exercise capacity (Ͻ4 nuclear imaging (dipyridamole or adenosine thal- METs). Patients with major clinical predictors (un- lium) or echocardiography (dobutamine echocardi- stable coronary syndromes, decompensated heart ography). For the most part, the results are compa- failure, severe valvular heart disease, or hemody- rable,11,12 with both having excellent negative namically significant arrhythmias) should not un- predictive values (NPV Ͼ 95%) but poor positive dergo elective surgery without further workup or predictive values (PPV Ͻ 20%); however, dobut- treatment. The ACP guidelines use the Detsky3 amine echocardiography tends to have fewer false modified CRI and “low-risk variables” to suggest positives. Dipyridamole or adenosine testing is rel- any need for further testing depending on type of atively contraindicated with bronchospasm and surgery (vascular or nonvascular). At times these 2 COPD but is preferred over exercise or dobutamine guidelines offer conflicting recommendations, with for patients with a left bundle-branch block. Sus- the ACC more likely than the ACP to recommend pected critical aortic stenosis is a contraindication NIT. The RCRI, which was developed prospectively to stress testing. Positive noninvasive findings and has been validated, uses 6 predictors of major should result in prophylactic measures, either med- cardiac complications—high-risk surgery, coronary ical therapy or an invasive procedure. artery disease, stroke, congestive heart failure, dia- betes mellitus requiring insulin, and serum creati- CORONARY REVASCULARIZATION nine Ͼ 2 mg/dL. Patients with 0 or 1 risk factors are Coronary Artery Bypass Grafting considered at low risk, those with 2 risk factors at Observational studies have shown that patients moderate risk, and those with 3 or more risk factors with CAD (in the CASS study) treated by coronary at high risk (Ն10% complication rate). Although the artery bypass grafting (CABG) surgery versus had a RCRI does not make recommendations about lower mortality (0.9% vs. 2.4%) and fewer nonfatal Preoperative Cardiac Risk Stratification 2007 / Cohen and Auerbach 175 TABLE 1 Summary of Recommendations for Preoperative Risk Stratification 1. Evaluate the patient for new or unstable cardiopulmonary symptoms, specifically those that would prompt evaluation in the absence of a potential surgery. ● NEW or UNSTABLE SYMPTOMS AND ELECTIVE SURGERY: 3 Pursue additional testing as clinical judgment dictates. 3 Delay in surgery may be appropriate. ● NEW OR UNSTABLE SYMPTOMS AND EMERGENT/URGENT SURGERY: 3 Weigh medical risks/benefits of surgery with patient and family, surgeon, and anesthesia. 3 Proceed to surgery with close attention to postoperative monitoring for ischemia. 3 Begin cardioprotective agents whenever appropriate. ● NO NEW SYMPTOMS: 3 Proceed to clinical risk stratification. 2. Use a structured clinical risk stratification rule. ● Low-risk patients (0-1 revised cardiac risk index criteria) 3 Proceed to surgery, no need for beta-blockers or additional noninvasive stress testing. ● Moderate-risk patients (2 revised cardiac risk index criteria) 3 Assess for functional status and current level of anginal symptoms and/or claudication. ● Patients who have a history of angina or claudication but no longer have these symptoms because of decreasing functional status (Ͻ 4 METS) should be considered for noninvasive stress testing. ● Patients who have good functional status regardless of history of angina or claudication do not require additional testing and should