Perioperative Cardiac Assessment for Noncardiac Surgery
Eight Steps to the Best Possible Outcome
The prevalence of cardiovascular disease in the United States1 and the number of noncardiac surgical procedures performed are progressively increasing. Preoperative risk assessment is an important step in reducing perioperative morbidity and mortality in patients undergoing noncardiac surgery. Successful perioperative evaluation is best achieved by combining an integrated multidisciplinary approach with good communication between the patient, primary care physician, anesthesiologist, consultant, and surgeon. The goal of appropriate preoperative evaluation and therapy should be to not only improve immediate periprocedural outcomes but also to improve long term clinical outcome.
Eight Steps to the Optimal Perioperative Outcome
A 68-year-old man with diabetes, hyperlipidemia, and lifestyle-limiting claudication requires aorto-bifemoral bypass surgery. He has a history of prior myocardial infarction 6 years ago and has had infrequent episodes of angina since then. His ability to perform physical activity is limited by claudication. He is currently taking aspirin, long-acting nitrates, glyburide, and lovastatin. Does he need further evaluation before his elective surgery? What can be done to minimize his risk of perioperative complications?
(1) Assess the Patient’s Clinical Features
The history and physical examination should emphasize identification of markers of cardiac risk and assess the patient’s cardiac status. High-risk cardiac conditions include recent myocardial infarction (MI), decompensated heart failure (HF), unstable angina, symptomatic arrhythmias, and symptomatic valvular heart disease. The patient’s underlying cardiac conditions, although apparently stable at present, may become manifest during perioperative stresses. Such conditions include stable angina, distant MI, prior HF, or moderate valvular disease. One should also identify serious comorbid conditions such as diabetes, stroke, renal insufficiency, and pulmonary disease because these illnesses may also affect periprocedural outcomes. Table 1 lists the factors that increase the risk of perioperative cardiac complications in patients undergoing noncardiac surgery.2
(2) Evaluate Functional Status
The history should assess functional capacity (the ability to climb stairs, do one’s own housework, perform regular exercise, etc). Patients who are able to exercise on a regular basis without limitations generally have sufficient cardiovascular reserve to withstand very stressful operations. Conversely, those with limited exercise capacity may have poor cardiovascular reserve, which may become manifest after noncardiac surgery. Poor functional status is associated with a worse short- and long-term outcome in patients undergoing noncardiac surgery.
(3) Consider the Patient’s Surgery-Specific Risk
The type of surgery has important implications for perioperative risk. Table 2 categorizes surgery-specific risk into high-, intermediate-, and low-risk categories. Emergency surgery, particularly in the elderly, is associated with a high risk. Patients undergoing vascular surgery constitute another high-risk group, in part because of concomitant coronary artery disease. Fleisher et al3 demonstrated that aortic and infrainguinal surgery are each associated with high 30-day and 1-year mortality. Extensive surgical procedures, particularly those in the abdomen or thorax and those associated with large volume shifts and/or blood loss, are considered to be higher risk.
(4) Decide if Further Noninvasive Evaluation Is Needed
Consideration of steps 1, 2, and 3 helps the clinician determine if further noninvasive evaluation is likely to be helpful. Patient who are at low risk based on clinical features, functional status, and proposed low-risk surgery do not generally require any further evaluation. In contrast, patients who are deemed high-risk based on clinical features, have poor functional status, and are being considered for high-risk surgery may benefit from further evaluation. On the basis of the prior steps, intermediate risk patients may be empirically treated with β-blocker therapy or may undergo noninvasive testing. Individuals with more than 3 clinical risk factors and extensive myocardial ischemia on preoperative stress imaging testing appear to have a high complication rate even with effective β-blocker therapy and should be considered for invasive evaluation and coronary revascularization (Figure).4 In general, noninvasive testing is most useful in intermediate risk patients.
(5) Decide When to Recommend Invasive Evaluation
In patients with unstable angina or evidence of residual ischemia after recent MI, coronary angiography is often indicated. In general, indications for preoperative coronary angiography are similar to those identified for the nonoperative setting and include evidence of high risk based on noninvasive testing, angina unresponsive to adequate medical therapy, unstable angina, and proposed intermediate-risk or high-risk noncardiac surgery after equivocal noninvasive test results. This stepwise approach to preoperative assessment allows judicious use of both noninvasive and invasive procedures while preserving a low rate of cardiac complications.5
Coronary stents are now used in more than 80% of percutaneous coronary interventions (PCIs). Use of stents during PCI immediately before noncardiac surgery presents a unique challenge because of the risk of stent thrombosis and perioperative bleeding during the initial post-surgical period.6 Serious bleeding may result from dual antiplatelet therapy, which is routine after PCI stenting. Coronary thrombosis may occur in those who do not receive 4 full weeks of dual antiplatelet therapy after stenting.6 The American College of Cardiology/American Heart Association guideline recommends that surgeons wait at least 2 weeks, preferably 4 weeks, after coronary stenting to perform noncardiac surgery to allow complete endothelization and a full course of antiplatelet therapy to be given. Post-stenting therapy currently includes a combination of aspirin and clopidogrel for at least 4 weeks, followed by aspirin for an indefinite period.
(6) Optimize Medical Therapy
Patients should be receiving optimal medical therapy, both perioperatively and long-term, based on their underlying cardiac condition. Individuals with angina should receive aspirin, β-blockers, and nitrates, and if there is evidence of ischemia despite β-blockers, calcium channel blockers should be considered. Individuals who have had a prior MI should generally be taking aspirin, β-blockers, and frequently a statin. For those with HF, an angiotensin-converting enzyme inhibitor or an angiotensin-receptor blocker should be used when the left ventricular ejection fraction is less than 40%. Such patients should also be taking β-blockers. In hypertensive individuals, β-blockers before surgery may be particularly effective. In individuals with diabetes, optimizing blood pressure control with angiotensin-receptor blockers and a β-blocker represents a desirable combination. Table 1 lists the independent clinical predictors of perioperative cardiac complications and the potential role of β-blockers in each circumstance. Patients with symptomatic aortic or mitral stenosis should preferably have the valve treated definitively before elective noncardiac surgery. Individuals with valvular regurgitation should generally receive vasodilator therapy to decrease afterload and reduce regurgitant volume. Current smokers should be strongly counseled to stop before surgery to reduce potential cardiac and pulmonary complications.
For the high-risk coronary patient, the β-blocker dose should be titrated to achieve a target heart of 60 beats per minute or less, anemia should be promptly identified and corrected, and postoperative pain should be well controlled with adequate doses of analgesics to reduce catecholamine levels. These individuals should generally also continue taking aspirin, a statin, and, when indicated, an angiotensin-converting enzyme inhibitor. Inotropic agents, which increase myocardial oxygen demand, should be avoided whenever possible.
(7) Perform Appropriate Perioperative Surveillance
In patients with known or suspected coronary artery disease, ECGs should be obtained at baseline, immediately after surgery, and on the first 2 days after surgery.7 Biomarkers such as creatine kinase-MB and troponin should be measured in high-risk patients after surgery and on the following day. The possibility of perioperative ischemia or MI can then be estimated on the basis of the magnitude of biomarker elevation, new ECG abnormalities, hemodynamic instability, and quality and intensity of chest pain or other symptoms. Antiplatelet agents should be reinstituted postoperatively as soon as feasible to reduce cardiovascular risk. Patients who develop ST-elevation MI should be considered for urgent angiography and coronary reperfusion, whereas patients with non–ST-elevation MI should undergo risk stratification after initial stabilization with intensive medical therapy. Individuals who develop HF after surgery should be evaluated for the pathophysiology of HF and treated on the basis of the precipitating or underlying cause.
(8) Design Maximal Long-Term Therapy
The evaluation before and after noncardiac surgery should be used as an opportunity for assessment and management of modifiable risk factors for coronary artery disease, heart failure, hypertension, stroke, and other cardiovascular diseases. Assessment for hypercholesterolemia, smoking, hypertension, diabetes, physical inactivity, peripheral vascular disease, cardiac murmurs, arrhythmias, conduction abnormalities, and/or perioperative ischemia may lead to evaluation and treatments that reduce future cardiovascular risk. Patients who experience repetitive postoperative myocardial ischemia and/or sustain a perioperative MI are at substantially elevated long-term cardiac risk and should be a particular focus for risk factor interventions and risk stratification with noninvasive testing and/or coronary angiography. Patients should be instructed on the benefits of regular exercise and complete smoking cessation and should receive optimal medical therapy for identified cardiac conditions in the form of antiplatelet therapy, β-blockers, angiotensin-converting enzyme inhibitors, and lipid lowering therapy when appropriate.
Case: Clinical Results and Conclusions
This patient was at elevated cardiac risk based on his clinical features, limited functional status, and planned high-risk vascular surgery. He underwent a dobutamine-stress echocardiogram that revealed extensive anterolateral ischemia. Coronary angiography revealed 90% stenosis in the proximal portion of the left anterior descending artery. He underwent successful coronary stenting and began taking metoprolol, ramipril, and clopidogrel in addition to his existing regimen of aspirin, nitrates, glyburide, and lovastatin. Clopidogrel was administered for 4 weeks, and the patient underwent elective vascular surgery 1 week after stopping clopidogrel. His postoperative course was uneventful, with no evidence of myocardial ischemia, and he was discharged on the fourth post-operative day.
Comprehensive preoperative evaluation and appropriate therapy may significantly improve periprocedural and long-term outcomes. It is important to determine the urgency of noncardiac surgery, and in many cases, patient or surgery-specific factors dictate immediate surgery that may not allow further cardiac assessment or treatment. Perioperative medical management, surveillance, and postoperative risk stratification are appropriate in these patients and may also improve long-term outcomes. Patients with coronary artery bypass grafting in the past 5 years or PCI from 6 months to 5 years previously who free of clinical evidence of ischemia may often undergo surgery without further testing, particularly if functionally very active.8 On the other hand, patients with unstable coronary syndromes, decompensated HF, significant arrhythmias, or severe valvular heart disease scheduled for elective noncardiac surgery should have surgery cancelled or delayed until the cardiac problem has been clarified and treated. In the absence of contraindications, β-blocker therapy should be considered for all patients at high risk for coronary events who are scheduled to undergo noncardiac surgery. Whenever possible, this treatment should be initiated days to weeks before surgery to achieve effective β-blockade, eg, a preoperative heart rate of 60 beats per minute or less.
Ironically, many patients presenting for noncardiac surgery have not had a meticulous cardiovascular evaluation recently (or ever!). Furthermore, many such patients will undergo a procedure that creates a sustained cardiovascular stress quite beyond what they may experience in daily life. Therefore, the cardiovascular consultant must identify underlying conditions and evaluate and treat them using cost-effective and evidence-based guidelines, thereby benefiting patients both for the short-term and long-term.9