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NewsletterApril 2002 Newsletter ACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery Executive Summary: a report of the ACC/AHA task force on practice guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery)
Eagle KA, Berger PB, Calkins H, Chaitman BR, Ewy GA, Fleischmann KE, Fleisher LA, Froehlich JB, Gusberg RJ, Leppo JA, Ryan T, Schlant RC, Winters WL, Jr. J Am Coll Cardiol 2002; 39:542-553
Reviewer: KW Tim Park, MD
This article is a summary of an update of the 1996 ACC/AHA guidelines for perioperative cardiovascular evaluation for noncardiac surgery. The full version of the update is available on the ACC website: http://www.acc.org and the version with new texts in red and deleted texts in strikeout is available on http://www.acc.org/clinical/guidelines/perio/update /periupdate_index.htm. The guidelines and update were prepared by representatives of the disciplines of general and interventional cardiology, noninvasive testing, vascular medicine, vascular surgery, anesthesiology, and arrhythmia management. The overriding theme of the update is that "preoperative intervention is rarely necessary simply to lower the risk of surgery unless such intervention is indicated irrespective of the preoperative context." 1996 Guidelines: The original guidelines provided a simple 8-step algorithm for determining the need for preoperative cardiac evaluation. The 8 steps were as follows: Step 1: What is the urgency of the surgery? If emergent, take the patient to the OR and, if indicated, perform postoperative cardiac risk stratification and risk factor management. Step 2: Has the patient had coronary revascularization within 5 years without recurrence of symptoms or signs? If so, no further testing is indicated preoperatively. Step 3: Has the patient had a favorable coronary evaluation within 2 years? If so, no further testing is indicated preoperatively. If not, consider the presence of clinical predictors of risk, patient's functional capacity, and risk of the proposed surgery. Step 4: Does the patient have a major clinical predictor such as unstable coronary syndrome (unstable angina or myocardial infarction (MI) within a month), decompensated heart failure (HF), significant arrhythmias, and severe valvular disease? If so, consider delay or cancellation of surgery for further preoperative cardiac testing/management. Step 5: In the absence of a major clinical predictor, does the patient have an intermediate clinical predictor such as stable angina, prior MI > 1 month, compensated HF, diabetes mellitus, and renal insufficiency or a minor clinical predictor such as advanced age, abnormal ECG, rhythm other than sinus, low functional capacity, history of stroke, or uncontrolled systemic hypertension? If an intermediate clinical predictor, go to step 6. If a minor clinical predictor or none, go to step 7. Step 6: Is the patient undergoing a high-risk surgery generally associated with > 5 % risk of perioperative cardiac events (e.g., aortic or peripheral vascular surgery) or is the patient's functional status poor, being unable to perform ³ 4 METS of activity (e.g., going up a flight of stairs with a bag of groceries) and is the patient not undergoing a low-risk surgery generally associated with < 1 % risk of cardiac events? If so, go to step 8. If not, go to OR. Step 7: Is the patient undergoing a high-risk surgery and is the patient's functional status poor? If so, go to step 8. If not, go to OR. Step 8: Perform a noninvasive testing for further risk stratification and testing/management before deciding whether to proceed with surgery. Updates: Algorithm-based preop-erative cardiac screening has been shown to be effective in lowering perioperative morbidity and mortality and to be cost-effective (1-4). The same 8-step algorithm has been retained in the updated guidelines. Some of the salient changes in the updated guidelines compared to 1996 are outlined below:
a. Whereas in the past relatively high blood glucose levels were considered acceptable rather than risking hypoglycemia, the update recommends aggressive regimen of glucose control, even using insulin infusions, in the perioperative period. Such an aggressive regimen has been shown to reduce infections in cardiac and noncardiac surgery (5,6), but has not been to influence cardiovascular outcome. b. Preoperative creatinine as low as 1.4 mg/dl and 2.0 mg/dl may be a risk factor for postoperative renal dysfunction (7) and cardiac complications (8), respectively. Even in patients with increased blood urea nitrogen and creatinine, ACE inhibitors or angiotensin receptor blockers should not be discontinued perioperatively, because they improve survival in patients with HF. Candidates for either kidney or kidney-pancreas transplantation commonly have coronary artery disease (CAD), especially if they have concomitant diabetes. Dipyridamole-thallium imaging studies can predict adverse cardiac events in such patients (9). c. While the update continues to recommend a conservative approach with transfusion, it also specifies that hematocrits < 28 % are associated with an increase in perioperative myocardial ischemia and cardiac events in prostate and vascular surgery (10-12). d. Surgical risk categories are the same as before. However, it was recognized that urologic and orthopedic surgeries would be at the lower end of the intermediate risk surgery group. e. While hypertension continues to be classified as a minor clinical predictor, the update states that uncontrolled stage 3 hypertension (systolic ³ 180 or diastolic ³ 100) should be controlled preoperatively. Such a control may be achieved over days or more rapidly using agents such as b-adrenergic blockers. f. While severe valvular diseases continue to be classified as major clinical predictors of cardiac risk, rationale on why they should warrant automatic consideration of delay or cancellation of surgery per step 4 of the algorithm is not given in the update. The update quotes a study showing an increased incidence of HF in patients with hypertrophic obstructive cardiomyopathy (13). Two studies quoted in the update actually showed that critical aortic stenosis might not be associated with an increased incidence of perioperative cardiac events in non-emergency noncardiac operations (14, 15). The update states that patients with severe valvular regurgitation tend to tolerate surgical stresses better than those with severe valvular stenosis, with appropriate medical therapy and monitoring. g. Evidence is presented for the benefit of perioperative use of b-adrenergic blockers or a-2 adrenergic agonists in reducing perioperative cardiac events and perhaps even conferring long-term benefit. In addition, b-adrenergic blockers are touted for control of atrial fibrillation and for reducing perioperative arrhythmias. h. Although preoperative frequent premature ventricular contractions (PVC's) and nonsustained ventricular tachycardia may increase the risk of significant arrhythmias in the perioperative period, they do not increase the risk of perioperative nonfatal MI or cardiac death (16,17) i. In interpreting the result of a stress test, one should consider not only whether the test is positive or negative, but also the ischemic threshold at which the test becomes positive, the size of defect, and the reversibility of the defect. A positive test at low workloads or with a moderate (20 25 % of left ventricular mass) or larger defect size indicates a high risk. In patients with left bundle branch block, pharmacologic stress testing with adenosine or dipyridamole is preferable to dobutamine or exercise imaging. j. The role of prophylactic preoperative percutaneous coronary intervention (PCI) remains unclear. No benefit was seen if the PCI was less than 90 days before noncardiac surgery in a retrospective review (18). Performing noncardiac surgery too soon (4 weeks) after PCI may even add to the risk of either rethrombosis or excessive bleeding (19). On the other hand, there may be a long-term benefit of revascularization by PCI. k. Routine use of TEE in noncardiac surgery is not recommended. Routine use of a PA catheter in noncardiac surgery is not recommended, although its use may benefit high-risk patients. Decision on the use of the PA catheter should be based on patient disease, surgical procedure, and practice setting, as has also been recommended by ASA (20). Physician education on the interpretation of the PA catheter data is critical to achieve optimal benefit without harm. l. Perioperative hypothermia is an independent risk factor of major cardiac events. Active warming to keep the core temperature > 35.5 oC may reduce the incidence of cardiac events (21,22). m. In patients without documented CAD, perioperative surveillance of MI should be restricted to those who develop perioperative signs of cardiovascular dysfunction. In patients with known CAD or at high or intermediate risk who are undergoing high or intermediate risk surgery, obtaining ECG at baseline, immediately postoperatively, and daily for two days may be cost-effective. In addition, cardiac troponin at 24 hours postoperatively and on day 4 or at hospital discharge may be done (23). Whereas elevation of troponin T predicted late cardiac events, CK-MB did not (24). n. Regarding postoperative arrhythmias, a sustained narrow-complex tachycardia is usually terminated with vagal maneuvers or IV adenosine. Atrial fibrillation or flutter is best treated with a b-adrenergic blocker, though diltiazem and digoxin, in that order, may be tried to control ventricular rate. Cardioversion of atrial fibrillation is not recommended until the underlying cause has been corrected. Unifocal or multifocal PVC's do not merit therapy, unless very frequent or prolonged enough to be symptomatic or result in hemodynamic compromise. In case of bradyarrhythmias, one should look for the underlying cause such as ischemia, hypoxemia, electrolyte disturbance, and certain medications. Although avoidance of hypokalemia and hypomagnesemia may reduce the perioperative incidence of arrhythmias, acute preoperative repletion of potassium in an asymptomatic patient may be associated with greater risk than benefits (25).
References: 1. Bartels C, et al. Circulation 1997; 95:2473-5
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