Monday, April 5, 2021

Cardiac Risk Assessment Prior to Noncardiac Surgery Case File

Posted By: Medical Group - 4/05/2021 Post Author : Medical Group Post Date : Monday, April 5, 2021 Post Time : 4/05/2021
Cardiac Risk Assessment Prior to Noncardiac Surgery Case File
Eugene C. Toy, Md, Michael d . Faulx, Md

Case 24
A 70- year-old woman presents to your office for preoperative cardiovascular risk assessment prior to elective hip replacement. Her medical history is remarkable for hypertension, diabetes mellitus, chronic kidney disease, obesity, and osteoarthritis. She has no history of heart disease. She denies chest pain, orthopnea, or PND, but she does report mild dyspnea with exertion that has gradually progressed over the past 6 months. This corresponds with reduced physical activity secondary to hip pain. She can walk unassisted at a slow pace for one city block before stopping because of hip pain. The patient is a retired school teacher who has never smoked cigarettes. She drinks alcohol rarely and has no known drug allergies. Her medications include aspirin, lisinopril, metoprolol, glargine insulin, rosuvastatin, naproxen as needed, and a multivitamin. Her examination is remarkable for the following: blood pressure 152/ 82 mmHg, pulse 78 bpm, respirations 16 breaths/min, and BMI 40 kg/m2. She is an obese Caucasian woman in no distress. There are no carotid bruits or obvious jugular venous distention. Cardiac auscultation is normal, and her chest is clear. She has mild bilateral ankle edema. Her office ECG is shown (Figure 24-1). Laboratory data include the following: sodium 135 mEq/L, potassium 4.1 mEq/L, BUN 32 mg/ dL, creatinine 2.1 mg/ dL, and hemoglobin 10.5 g/ dL.
  • How would you consult the patient on the cardiovascular risk in surgery ?
  • What additional testing would be helpful?
  • What can be done to reduce her perioperative cardiac risk?
Cardiac Risk Assessment Prior to Noncardiac Surgery

Figure 24-1. ECG for the main subject of this case.


Answer to Case 24:
Cardiac Risk Assessment Prior to Noncardiac Surgery

Summary: The patient is a 70-year-old obese woman with diabetes and limited functional capacity who is planning to have elective hip replacement. She has no history of heart disease, and she denies symptoms that strongly suggest an active cardiovascular condition; however, she does report NYHA class II dyspnea, which may simply be due to deconditioning and obesity but can also be an “angina equivalent” symptom in women and patients with diabetes. Her physical examination is limited by her obesity, but it does not suggest the presence of structural heart disease or decompensated heart failure. Her resting ECG reveals nonspecific ST and T wave abnormalities possibly related to left ventricular hypertrophy. Recent laboratory assessment confirms the presence of stage 4 chronic kidney disease (glomerular filtration rate 23 mL/min).

In this case unit we will review the process of risk stratification from a cardiologist’s perspective, highlighting an approach to risk stratification that is jointly endorsed by the American Heart Association (AHA) and the American College of Cardiology (ACC). Management guidelines regarding preoperative risk assessment are also published by the American College of Physicians (ACP) and a number of subspecialty-oriented academic societies. Although these guidelines vary on certain points, there is generally agreement between them regarding major themes such as the importance of clinical risk prediction models to guide the use of noninvasive imaging and the judicious use of preoperative coronary revascularization.
  • Perioperative cardiac event risk: At risk for major perioperative cardiac event.
  • Additional testing: Noninvasive assessment for myocardial ischemia.
  • Reducing perioperative cardiac risk: Optimization of her blood pressure control.

ANALYSIS

Objectives
  1. Understand the purpose of risk stratification prior to noncardiac surgery.
  2. Know the clinical elements associated with increased perioperative cardiovascular risk.
  3. Review the process of risk stratification, including when to order additional imaging to assess for myocardial ischemia.
  4. Appreciate the limitations of the evidence related to perioperative risk reduction, including beta-blocker therapy and revascularization.
Considerations
This patient’s risk for major adverse cardiac events related to hip replacement is at least moderate. She has several robust risk factors for ischemic heart disease, and her lack of suggestive symptoms may be due to her limited functional capacity and inability to provoke ischemia in her daily life. The concern is that the stress of surgery combined with the pain, anemia, and immobility that follows it might create the “perfect storm” for cardiovascular complications to occur. Additional information obtained from a noninvasive test to assess for myocardial ischemia will allow for better risk stratification and aid the patient and the surgeon with respect to decision making. If high-risk features are discovered, then the surgery should be postponed to allow for additional study and possibly revascularization if high-risk coronary disease is found. Alternatively, she may be found to have no evidence of occult ischemic heart disease, in which case she may proceed with surgery with little concern for major adverse cardiac events. The purpose of risk stratification is to quantify the risk for adverse cardiac events as accurately as possible in order to allow the treating surgeon, anesthesiologist, and patient to compare the cardiac risk related to surgery to the patient’s risk for harm without surgery. The risk stratification process also provides the cardiologist with an opportunity to make recommendations regarding risk attenuation and medical optimization. This patient has suboptimally controlled blood pressure, and she may benefit from optimization of her antihypertensive medications prior to surgery.

Approach To:
Preoperative Risk Assessment

DEFINITIONS

REVISED CARDIAC RISK INDEX (RCRI): Prospectively validated scoring system consisting of six clinical risk variables that were found to be associated with increased cardiac risk by multivariable analysis.

FUNCTIONAL CAPACITY: Ability to perform physical activities without symptoms or assistance; poor functional capacity is associated with an approximate twofold increase in the risk for major adverse cardiac events (MACEs). Poor functional capacity is typically defined as an inability to achieve 4 metabolic equivalents (METs), which is roughly the effort required to walk four blocks or climb two flights of stairs without stopping.

HIGH-RISK MYOCARDIAL ISCHEMIA: Findings on a noninvasive imaging study that imply the presence of severe left main, proximal left anterior descending, or multivessel coronary artery disease. Examples include exercise-induced hypotension, marked ST segment deviation with exercise, reduced left ventricular systolic function, left ventricular dilatation with exercise, or five or more ischemic myocardial segments during imaging.

PERCUTANEOUS CORONARY INTERVENTION (PCI): Method of coronary artery revascularization that includes balloon angioplasty and stenting. Although PCI provides immediate coronary revascularization with relatively little risk, intracoronary stenting necessitates the use of potent antiplatelet therapy for at least 4 weeks and ideally 1 year to prevent stent thrombosis. The issue of recent stenting and the need for antiplatelet therapy in patients who require noncardiac surgery has become a major challenge in the field of perioperative medicine.

DUAL-ANTIPLATELET THERAPY (DAPT): The combination of aspirin and a second, more potent antiplatelet agent prescribed to prevent acute thrombosis of intracoronary stents. Current agents include clopidogrel, prasugrel, and ticagrelor.

ACUTE STENT THROMBOSIS: Sudden thrombosis of an intracoronary stent, typically triggered by premature withdrawal of dual antiplatelet therapy or poor apposition of the stent and the coronary arterial wall. Patients with intracoronary stents are vulnerable to stent thrombosis in the perioperative period following preoperative cessation of antiplatelet therapy and the transient increase in platelet activation and hypercoagulability that accompanies the stress of surgery. Stent thrombosis almost always results in myocardial infarction, and the mortality associated with acute postoperative stent thrombosis can approach 50%.

CLINICAL APPROACH

Overview
Cardiovascular risk assessment and management prior to noncardiac surgery can be challenging. Part of the challenge relates to the relative paucity of prospective data regarding benefit from therapies intended to specifically reduce risk such as coronary revascularization and beta-blocker therapy. Thus, the focus of risk assessment is to define risk so that the patient and surgeon may weigh the risks of surgery against the risk of not having surgery. The preoperative visit also affords the cardiologist an opportunity to identify and treat previously undiagnosed heart disease in at-risk patients and to optimize established cardiovascular diseases such as heart failure, ischemic heart disease, and hypertension prior to surgery in order to reduce risk. The following paragraphs will review a stepwise approach to preoperative risk assessment that is recommended by the ACC/AHA guidelines (Figure 24-2).

Clinical Risk Assessment
The risk for cardiovascular events related to noncardiac surgeries can be attributed to patient-specific factors and surgery-specific factors. Patient-specific factors include major active cardiovascular signs and symptoms, medical diagnoses such as cardiovascular disease, or its risk factors and limited functional capacity. Surgeryspecific factors include the length of the surgery, potential for blood loss, and risk for major fluctuations in intravascular volume or hemodynamic measures such as heart rate or blood pressure.

Patients with symptoms suggestive of active severe cardiovascular disease are at high risk for perioperative cardiac events related to noncardiac surgery. These major risk predictors include unstable coronary syndromes, decompensated heart failure, severe valvular heart disease, and dangerous arrhythmias (Table 24-1). In these cases it is usually appropriate to delay surgery to allow the active cardiac issue to be properly treated. The obvious exception would be the high-risk patient who requires emergency surgery to prevent death or major disability; in those cases

preoperative cardiac risk assessment

Figure 24-2. Stepwise approach to preoperative cardiac risk assessment based on current guidelines (Fleisher et al. 2009). (OR, operating room; METs, metabolic equivalents; RCRI, revised cardiac risk index.)

major clinical predictors

Abbreviations: AV, atrioventricular; AVA, aortic valve area; CCS, Canadian Cardiovascular Society; MVA, mitral valve area; NyHA, New york Heart Association.

left ventricular ejection fraction

Abbreviations: CCS, Canadian Cardiovascular Society; LVEF, left ventricular ejection fraction; RCRI, revised cardiac risk index; TIA, transient ischemic attack.
[Data from Lee TH, Marcantonio ER, Mangione CM, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation. 1999;100(10):1043.]

surgery is often performed with close inpatient monitoring and comanagement of the patient by the surgical and cardiac teams in an intensive care setting.

Patients without major cardiac risk predictors may still be at relatively high risk for adverse cardiac events related to noncardiac surgery. Identifying these patients prior to surgery is difficult because they may not have overt symptoms or a previously diagnosed cardiovascular problem. Multivariate analyses performed on cohorts of patients undergoing noncardiac surgery in the 1970s identified several clinical
factors that were individually associated with an increased risk for postoperative cardiovascular events. In the decades that followed variables were added and others refined, resulting in the creation of several risk stratification models such as the revised cardiac risk index (RCRI). The RCRI employs six equally weighted clinical features that are predictive of postoperative cardiac events (Table 24-2). Each feature is assigned one point, and the points are added to produce the RCRI. The validity of the RCRI as a risk predictor has been prospectively confirmed in cohorts of patients undergoing a wide range of noncardiac surgeries (Table 24-3).

performance of the revised cardiac risk index

Abbreviations: CHB, complete heart block; MI, myocardial infarction; VF, ventricular fibrillation.
Note: “Major Complications” data were obtained from Lee et al. (1999); “Mortality and Morbidity” data were obtained from Devereau et al. (2005).

The RCRI performs well for most patients undergoing noncardiac surgery, particularly thoracic and abdominal surgeries. It may slightly overestimate risk in patients undergoing orthopedic surgery and tends to underestimate the risk associated with major vascular surgery. Nonetheless, its generally accurate performance and simplicity have made the RCRI a widely used tool in the assessment of preoperative cardiac risk.

Functional capacity is also another important factor in the assessment of risk. Patients with reduced functional capacity have a nearly twofold increase in the risk for adverse postoperative cardiac events compared to those who have better physical ability. Poor functional capacity is generally defined as the inability to walk four city blocks or climb two flights of stairs without rest or assistance. This level of exercise is equivalent to four metabolic equivalents (METs).

Surgery-specific risk is driven by the nature of the surgery and the urgency with which the surgery needs to be performed. Low-risk surgeries include most ambulatory outpatient surgeries, superficial surgeries (dermatologic and breast procedures), endoscopic procedures, and cataract surgery. These procedures are associated with a risk for death and nonfatal myocardial infarction of <1%, and preoperative testing or medical therapy is seldom required. High-risk surgeries include open aortic surgeries, peripheral revascularization (other than carotid endarterectomy), and lengthy surgeries associated with labile hemodynamics and marked fluid shifts; these procedures carry an estimated risk for death or nonfatal myocardial infarction of ≥5% . Surgeries performed under emergent circumstances are also considered high risk.

Noninvasive Imaging for Risk Stratification
Following clinical risk assessment, many patients are found to be at moderate or high risk for adverse cardiac events related to surgery. The risk for these patients can vary widely, and in these cases a more precise risk estimate is needed to guide surgical planning. For example, a patient with an RCRI score of 3 and poor functional capacity who is planning for an elective hernia repair has an estimated risk for death, nonfatal infarction, or nonfatal cardiac arrest somewhere between 3 and 8%. A normal dobutamine echocardiogram would be associated with a risk in the 1–2% range, whereas a high-risk finding on this study risk would indicate a risk of >10%. For this reason moderate- or high-risk patients, particularly those with poor functional capacity, may benefit from noninvasive assessment for occult myocardial ischemia.

Noninvasive assessment for myocardial ischemia includes exercise testing and imaging studies that employ pharmacologic agents to induce coronary vasodilatation or increase heart rate and contractility. Exercise testing is always preferable to pharmacologic stimulation in patients who can safely exercise, because functional capacity itself aids in the prediction of cardiac risk. These studies are most helpful when they are normal or have findings suggestive of high-risk coronary artery disease (reduced left ventricular systolic function, findings consistent with left main, proximal left anterior descending, or three-vessel coronary disease). Normal noninvasive ischemic studies have excellent negative predictive value, and studies with high-risk findings generally warrant surgical delay to allow for coronary angiography and revascularization if appropriate.

Abnormal studies without high-risk features have limited positive predictive value for postoperative cardiac events; these studies may or may not be associated with a level of risk greater than that provided by the RCRI. This variability is due to the fact that test abnormalities vary with respect to their implied level of risk, and all imaging studies have a defined false-positive rate. For example, an intermediaterisk patient with an adenosine myocardial perfusion study suggestive of two apical segments of myocardial ischemia may not be at any greater risk for adverse effects because this finding might be a false positive (breast attenuation), or it may be a true positive but indicative of limited ischemia that, if properly medically managed, may not be associated with a greater risk for perioperative events.

Noninvasive assessment for myocardial ischemia is usually performed with an imaging modality such as echocardiography or nuclear imaging with single-photon emission computed tomography (SPECT) or positron emission tomography (PET). There is no clear consensus regarding which modality is better, and both provide comparable information. Echocardiography has the advantage of providing information regarding valvular function, structural cardiac abnormalities, and pulmonary artery pressure in patients who raise clinical concern for these disorders. In patients without such concerns (eg, no murmurs, unexplained heart failure symptoms, or findings consistent with pulmonary hypertension), there is no role for routine resting echocardiography.

Coronary angiography is seldom required for risk stratification in patients prior to noncardiac surgery. The major reason for this is the fact that preoperative coronary artery revascularization (percutaneous and surgical) has not been shown to reduce the risk for major adverse cardiac events in the peri- and postoperative period (see following section). The general rule applied to the use of angiography in the setting of preoperative risk assessment is to ask whether the patient has an indication for coronary angiography that is independent from his or her surgical evaluation. If the answer is “yes,” then an angiogram should be performed.

Risk Attenuation
Once the magnitude of a patient’s risk for major adverse cardiac events has been determined, the cardiologist should make appropriate recommendations regarding ways to attenuate risk. This can be challenging as there are little data to support the routine use of therapies such as revascularization and beta-blockers for the sole purpose of reducing the risk for postoperative cardiac events. Rather, risk attenuation can be achieved by a careful assessment and proper medical optimization of the patient’s established cardiac issues and risk factors.

Coronary Artery Revascularization
Preoperative coronary revascularization is appropriate in patients with symptoms consistent with acute coronary syndromes or severe chronic angina despite proper medical therapy. Similarly, patients with high-risk findings on a noninvasive study may derive a survival benefit from the revascularization of underlying left main or multivessel coronary disease, and thus revascularization would also be appropriate. However, these patients are the exception to the norm in the arena of preoperative cardiac risk, as a far greater number will be asymptomatic or have lower risk findings on noninvasive imaging.

Although it would seem sensible to perform coronary angiography and revascularization prior to surgery in any patient with an abnormal stress test or chronic stable angina, well-designed prospective randomized trials have consistently shown no significant benefit with respect to postoperative event rates in patients randomized to revascularization. As mentioned previously, the presence of ischemia on a noninvasive imaging study has a relatively poor positive predictive value for postoperative cardiac events. Many patients with chronic coronary artery disease have well-developed collateral blood supply to affected arteries that protects them from myocardial injury during times of stress. Also, with modern anesthetic techniques and aggressive management of postoperative issues such as pain and elevated blood pressure, patients may not experience a large increase in myocardial oxygen demand. Revascularization itself may also introduce complexity and harm. Coronary artery stenting usually delays surgery and obligates the patient to a period of dual-antiplatelet therapy (DAPT). Premature interruption of DAPT to reduce the risk for operative bleeding increases the risk for stent thrombosis. Continuation of DAPT to prevent stent thrombosis may increase the risk for perioperative bleeding. Surgical coronary revascularization carries its own significant risk for morbidity and also typically delays noncardiac surgery.

Beta-Blocker Therapy
Beta-blockers reduce blood pressure, heart rate, and myocardial oxygen demand. Beta-blocker therapy has clear benefit for patients with multiple cardiovascular disorders such as ischemic heart disease, stable angina, heart failure, and tachyarrhythmias, and their use in such patients prior to noncardiac surgery is clearly indicated. For this reason beta-blockers are continued throughout the perioperative period in patients who are already taking them and heart-rate–guided optimization of beta-blocker dosing in patients who have a clear indication for their use is also appropriate.

Given the previously mentioned findings, there has been interest in the use of beta-blockers in asymptomatic, at-risk patients in the preoperative period to reduce operative risk. However, current clinical evidence does not support the routine use of beta-blockers in patients who do not otherwise have an indication for beta-blocker therapy. A series of contemporary Dutch trials reported a significant benefit from the preoperative use of bisoprolol in a population of relatively high-risk patients undergoing vascular surgery; however, the legitimacy of the authors’ findings was questioned and the results of these studies were ultimately discredited. Another large randomized trial of metoprolol succinate given just prior to surgery to reduce the risk of postoperative cardiac events resulted in an increased risk for hypotension and stroke in the metoprolol-treated patients. However, the adverse events in this trial may have been related to the use of relatively high doses of long-acting betablockers in drug-na├»ve patients treated just prior to surgery. A well-designed and honestly run trial of cautiously titrated oral beta-blocker therapy prior to surgery may ultimately resolve the beta-blocker issue, but as of now there is no evidencebased indication for the use of beta-blockers in patients to reduce the risk for postoperative cardiac events.

Surgery Following Intracoronary Stenting
Occasionally patients who have recently undergone PCI with coronary artery stenting require noncardiac surgery. Although these patients have been revascularized, their recent PCI places them at risk for bleeding and perioperative myocardial infarction due to the use of dual-antiplatelet therapy (DAPT) and stent thrombosis, respectively. Current management guidelines recommend at least 12 months of uninterrupted DAPT following stenting to reduce the risk of stent thrombosis. Premature cessation of DAPT is associated with an increased risk for stent thrombosis, and this risk is magnified in the perioperative setting. Thus, withholding DAPT to prevent postoperative bleeding comes with a higher risk for stent thrombosis. The magnitude of this risk is time-dependent and highest in the first 6 weeks after PCI. The type of stent also matters; drug-eluting stents are felt to require a longer period of DAPT because they require more time to endothelialize than bare-metal stents. The precise risk for stent thrombosis is difficult to quantify, but what is well known is that stent thrombosis in the postoperative setting is devastating and associated with a mortality of approximately 40%.

Prevention of postoperative stent thrombosis should begin with a dialog between the patient, cardiologist, and surgeon so that all parties involved clearly appreciate the risk involved.

From a cardiac perspective, the safest option would be to proceed with surgery on DAPT and accept the potential for bleeding provided that the risk for fatal or uncontrollable bleeding is low. If continued DAPT is deemed too unsafe and the patient is far enough out from the scheduled PCI (>4 weeks after bare-metal stenting or >6 months after drug-eluting stenting), then the patient should remain on low-dose aspirin and stop taking the other antiplatelet agent prior to surgery. Surgery that needs to be performed soon after PCI poses a management challenge; such patients are often hospitalized for treatment with an intravenous short-acting antiplatelet agent or anticoagulant as the DAPT wears off. These “bridging” maneuvers are commonly done, but there use is empiric and not evidence-based.

CASE CORRELATION
  • See also Case 1 (acute coronary syndrome/STEMI), Case 2 (acute coronary syndrome/NSTEMI), Case 3 (cardiogenic shock), Case 6 (acute valvular regurgitation), Case 8 (hypertrophic obstructive cardiomyopathy), Case 10 (valvular stenosis), Case 16 (acute heart failure), and Case 17 (advanced heart failure).

COMPREHENSION QUESTIONS

24.1 All of the following factors are associated with an increased risk for perioperative
cardiac events in patients undergoing non-cardiac surgery except
A. History of myocardial infarction
B. History of heart failure
C. History of insulin-requiring diabetes
D. History of atrial fibrillation
E. History of moderate chronic kidney disease

24.2 A 60-year-old man presents to the intensive care unit with massive hematemesis and hypovolemic shock. His medical history includes an ischemic cardiomyopathy with prior myocardial infarction and a left ventricular ejection fraction of 30%. He describes baseline CCS class 3 angina symptoms despite appropriate medical therapy, and his physical examination is remarkable for pallor, tachycardia, an S3 gallop, and faint rales in the lung bases. His ECG reveals sinus tachycardia with inferior Q waves and 2-mm horizontal ST segment depression in the precordial leads. Following transfusion and resuscitation with intravenous fluids, he has an endoscopy that reveals a large duodenal ulcer with a visibly bleeding vessel that cannot be controlled by endoscopic therapy. General surgery is consulted and operative management of his bleeding ulcer is scheduled. You are asked to see him for preoperative cardiac risk assessment. Which of the following recommendation is most appropriate?
A. High risk for major cardiovascular complications; proceed with surgery immediately.
B. High risk for major cardiovascular complications; consider coronary angiogram prior to surgery to define his coronary anatomy.
C. High risk for major cardiovascular complications; consider noninvasive myocardial perfusion imaging to assess his burden of ischemia prior to surgery.
D. High risk for major cardiovascular complications; double his home dose of carvedilol to lower his cardiac risk and proceed with surgery.
E. High risk for major cardiovascular complications; recommend medical management only.

24.3 Which of the following statements regarding stress testing prior to noncardiac surgery is most accurate?
A. Nuclear imaging is superior to echocardiography for the prediction of postoperative cardiac events.
B. Vasodilator perfusion imaging is superior to treadmill exercise for the provocation of myocardial ischemia in preoperative patients.
C. A normal noninvasive test for myocardial ischemia has excellent negative predictive value for postoperative cardiac events.
D. Noninvasive testing for myocardial ischemia is indicated for better risk stratification in all moderate-risk patients with poor functional capacity.
E. An abnormal noninvasive test for myocardial ischemia has excellent positive predictive value for postoperative cardiac events.

24.4 Which of the following clinical findings is not considered a major predictor of cardiac events prior to noncardiac surgery?
A. First-degree AV block with a PR interval of 230 ms
B. Aortic stenosis with a valve area of 0.8 cm2
C. Heart failure with an S3 gallop and pulmonary rales
D. Coronary artery disease with a non-ST segment elevation myocardial infarction 3 weeks ago
E. Atrial flutter with a ventricular rate of 150 bpm


ANSWERS

24.1 D. History of atrial fibrillation. Although atrial fibrillation with an uncontrolled ventricular rate would be considered a major clinical risk predictor, a history of atrial fibrillation alone is not associated with an increased risk for perioperative cardiac events. Ischemic heart disease, heart failure, insulinrequiring diabetes, and moderate chronic kidney disease are all associated with increased operative risk and are features of the revised cardiac risk index.

24.2 A. High risk for major cardiovascular complications; proceed with surgery immediately. This patient is experiencing a major gastrointestinal bleed that has failed endoscopic therapy. He carries a high risk of death due to exsanguination without surgery that certainly exceeds his cardiac risk related to surgery, even in the face of major risk predictors such as severe chronic angina and features of decompensated heart failure. Coronary angiography is not indicated because this patient is not an appropriate candidate for percutaneous or surgical coronary revascularization. Noninvasive imaging is not indicated because his cardiac risk is already obviously high and the results of the study will not change management. Although beta-blockers are indicated for the management of heart failure and angina, it would be contraindicated to escalate beta-blocker therapy in a hypotensive patient in shock. Avoiding surgery would likely carry a mortality risk related to bleeding that is greater than the mortality related to cardiac causes.

24.3 C. A normal noninvasive test for myocardial ischemia has excellent negative predictive value for postoperative cardiac events. Studies comparing nuclear to echocardiographic assessment of ischemia have demonstrated no clear superiority of either modality, but exercise stress is generally considered superior to pharmacologic stimulation. Although many patients with moderate- risk predictors and low functional class might benefit from additional risk stratification, noninvasive studies should be performed only if the results are likely to change management, and this is clearly not the case for every patient. Abnormal imaging studies have relatively poor positive predictive value for postoperative cardiac events.

24.4 A. First-degree AV block with a PR interval of 230 ms. High-grade AV block is considered a major clinical risk marker and includes Mobitz type 2 second-degree AV block and third-degree AV block. Severe aortic stenosis, decompensated heart failure, recent myocardial infarction, and uncontrolled tachyarrhythmias are all major clinical risk indicators.


CLINICAL PEARLS
  • Clinical risk assessment tools such as the revised cardiac risk index can accurately estimate the risk for adverse cardiac events in most patients.
  • Noninvasive assessment for myocardial ischemia is appropriate for moderate-risk patients with poor functional status or high-risk patients undergoing moderate- or high-risk surgeries if the results will influence management.
  • Coronary angiography and revascularization is indicated in preoperative patients who have a separate and clear indication for revascularization that is independent from their need for risk stratification.
  • Preoperative beta-blocker therapy is recommended only in patients who have an independent indication for beta-blocker treatment. Doses should be titrated to a resting heart rate between 60 and 70 bpm, and hypotension should be avoided.
  • Chronic cardiovascular issues such as stable angina, heart failure, and tachyarrhythmias should be medically optimized prior to noncardiac surgery.
  • Postoperative stent thrombosis is an uncommon but potentially devastating complication of coronary artery disease treated with recent PCI.
References

Devereaux PJ, Goldman L, Cook DJ, et al. Perioperative cardiac events in patients undergoing noncardiac surgery: a review of the magnitude of the problem, the pathophysiology of the events and methods to estimate and communicate risk. Can Med Assoc J. 2005;173(6):627–634. 

Fleisher LA, Beckman JA, Brown KA, et al. 2009 ACCF/AHA focused update on perioperative beta blockade incorporated into the ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery: a report of the American college of cardiology foundation/ American heart association task force on practice guidelines. Circulation. 2009;120(21):e169. 

Hawn MT, Graham LA, Richman JS, et al. Risk of major adverse cardiac events following noncardiac surgery in patients with coronary stents. JAMA. 2013;310(14):1462. 

Lee TH, Marcantonio ER, Mangione CM, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation. 1999;100(10):1043. 

McFalls EO, Ward HB, Moritz TE, et al. Coronary-artery revascularization before elective major vascular surgery. N Engl J Med. 2004;351(27):2795. 

POISE Study Group; Devereaux PJ, Yang H, Yusuf S, et al. Effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery (POISE trial): a randomised controlled trial. Lancet. 2008;371(9627):1839.

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