Cardiology

CAD and Noncardiac Surgery

I. Coronary Artery Disease: What every physician needs to know.

Approximately 27 million patients undergo noncardiac surgical procedures each year in the U.S. Of those patients, 50,000 will suffer from a myocardial infarction (MI) and 20,000 patients will die due to cardiovascular causes in the perioperative setting.

With more than 6 million surgical procedures being performed in patients over the age of 65, the most vulnerable group for cardiac morbidity and mortality undergo the most surgical procedures. As our population continues to age, the number of noncardiac surgical procedures is expected to double in the next three decades. Thus expanding our understanding of cardiac risk is imperative to manage and mitigate complications in the perioperative period.

Risk assessment for the patient with known CAD or those with risk factors for CAD begins with assessing the acuity of the surgery. If surgery is an emergency and the patient's condition will worsen without immediate intervention, no further evaluation need take place (Class I, Level of evidence: C).

The patient should go to the operating room and attention should then be turned to perioperative-operative management to decrease the risk of cardiovascular complications. If surgery is not an emergency, the decision-making process becomes more complex. In this situation, the clinician should follow a systematic approach that incorporates the inherit risk of the surgery with the individual's risk of cardiovascular complications and functional status. This approach is well outlined in the American College of Cardiology and American Heart Association's 2014 Guidelines on Perioperative Cardiovascular Evaluation and Care for Noncardiac Surgery.

This approach factors in the type and risk of surgery, a patient's medical history including known CAD, risk factors, and comorbidities, functional status, and active symptoms that would place the patient at higher risk of cardiovascular complications. This step-wise approach helps the clinician understand, manage, and mitigate risk for those undergoing noncardiac surgery. It also improves our use of diagnostic testing prior to surgery as preoperative testing should be limited to those in whom the results would impact medical decision making and patient management.

II. Diagnostic Confirmation: Are you sure your patient has Coronary Artery Disease?

For patients undergoing noncardiac surgery, it is often known if the patient has CAD or risk factors for CAD, including hypertension, dyslipidemia, or diabetes mellitus. Additionally, comorbidities that also confer risk for perioperative cardiac events include cerebrovascular disease, peripheral vascular disease, congestive heart failure, valvular heart disease, significant arrhythmias (including high-grade AV block, ventricular arrhythmias, supraventricular arrhythmias with rapid ventricular response, and symptomatic bradycardia), renal insufficiency, pulmonary disease, and/or hematologic disorders, particularly anemia.

However, the presence of CAD, its risk factors, and/or comorbidities requires an individualized approach. One must consider the stability of the disease, treatment of CAD and its risk factors, as well as the patient's functional status and the type of surgery to be performed. All of these factors must be put into context to understand and mitigate the cardiac risk of a patient undergoing noncardiac surgery.

A. History Part I: Pattern Recognition:

A thorough patient history will help elucidate the severity of known cardiac conditions, including ischemic heart disease, heart failure, valvular heart disease, or significant arrhythmia. Special attention should be placed on the stability of coronary syndromes, history of syncope or presyncope, prior history and timing of MI, and presence of implantable devices such as pacemakers or defibrillators.

It will also help to uncover unknown cardiac conditions or comorbidities that place the patient at higher risk of cardiovascular disease, and complications, including renal insufficiency, diabetes mellitus, peripheral vascular disease, cerebrovascular disease, valvular heart disease, and pulmonary disease. Finally, a detailed patient history will also focus on current medical therapy, over-the-counter supplements, smoking history, illicit drug use, excess alcohol consumption, and a patient's functional status, which have all been correlated with perioperative complications.

B. History Part 2: Prevalence:

Currently, 27 million patients undergo noncardiac surgery annually in the U.S. Nearly 1 out of 4 surgeries is performed in patients over the age of 65. As it is estimated that the number of patients over the age of 65 could increase by approximately one third over the next 3 decades, the number of noncardiac surgeries being performed on those over 65 could increase to 12 million in this same time frame. Given the prevalence of cardiovascular disease increases with age, those at highest risk of perioperative cardiac morbidity and mortality will continue to undergo the most noncardiac procedures than any other age group.

C. History Part 3: Competing diagnoses that can mimic Coronary Artery Disease.

One of the most important areas of the history for patients undergoing noncardiac surgery is a detailed analysis of functional status. Prior research has shown good correlation between a patient's functional capacity and exercise treadmill testing.

This concept has been expressed in metabolic equivalents (METS) and is a measure of the energy needed to perform an activity. In general, patients who are only able to perform activities of daily living, such as clothing, bathing, and feeding themselves, are performing at a level less than 4 METS.

This cutoff point has been shown to correlate with a higher risk of cardiac morbidity and mortality in the perioperative setting. Conversely, those able to perform 4 METS or greater, are considered to be at lower risk for perioperative cardiovascular complications than patients who have difficulty functioning at this level. Activities that are considered to use 4 METS or more include walking up 1 to 2 flights of stairs without stopping, walking on level ground at 4 miles per hour, or performing moderate household activities such as vacuuming.

D. Physical Examination Findings.

Physical examination should focus on signs suggestive of valvular heart disease, decompensated heart failure, arrhythmia, and/or structural heart disease. The clinician should always evaluate volume status by thoroughly examining the jugular venous pressure and dependent edema, looking for signs of decompensated heart failure or significant valvular disease.

Careful auscultation of the chest and precordium may uncover valvular abnormalities, a third heart sound, arrhythmia, and pulmonary edema. An abdominal examination should focus on evidence of a pulsatile liver, enlarged spleen, and palpable abdominal aorta (particularly in those over the age of 50 with a smoking history).

E. What diagnostic tests should be performed?

In patients with known CAD or signs and symptoms suggestive of CAD, a baseline cardiac assessment should take place with a detailed focus on history and physical examination in the asymptomatic patient. This is particularly true for those over the age of 50 in whom higher risk is known.

Only tests that would affect management in the perioperative period should be ordered. These tests will vary depending on acute need for surgery, the type of surgery being performed, and the type and stability of the patient’s cardiac symptoms.

In general, only those patients in whom active cardiac conditions are present should undergo additional evaluation and treatment if surgery is not an emergency. These conditions include unstable coronary syndromes (e.g., unstable angina, non-ST elevation myocardial infarction, or ST-elevation myocardial infarction), decompensated heart failure, new onset heart failure, significant arrhythmia, or severe valvular disease. Otherwise, a review of electrolytes, renal function, hematocrit, platelets, glucose control, and coagulation markers should be performed in addition to review of ECG and any other recent testing that would aid in the decision making of the clinician.

ECG is routinely obtained for those undergoing noncardiac surgery; however, it is not always indicated. In asymptomatic patients undergoing low-risk surgery, ECG testing is not indicated. ECG testing is recommended for patients with at least one clinical risk factor and undergoing high-risk surgery. Clinical risk markers include ischemic heart disease, heart failure, cerebrovascular disease, diabetes mellitus, and renal insufficiency. ECG testing is also recommended for those who will have intermediate risk surgery and have known CAD, peripheral vascular disease, or cerebrovascular disease.

Routine use of echocardiography or nuclear imaging to assess left ventricular function is not recommended (Class III, Level of Evidence: B). For patients with unexplained dyspnea, worsening dyspnea, and/or a history of heart failure or decompensated heart failure, assessment of left ventricular (LV) function prior to surgery is reasonable, particularly if this knowledge is likely to affect patient management (Class IIa, Level of Evidence: C).

Use of stress testing prior to noncardiac surgery should be reserved for those patients in whom positive stress test results would affect the management of the patient in the perioperative setting. Stress testing may be indicated in patients with active cardiac conditions, such as unstable angina, decompensated heart failure, or severe and symptomatic valvular disease (Class I, Level of Evidence: B).

For patients with elevated risk and excellent (>10 METs) functional capacity, it is reasonable to forgo further exercise testing with cardiac imaging and proceed to surgery (Class IIa, Level of Evidence: B). Stress testing is reasonable for patients with elevated risk and poor (<4 METs) or unknown functional capacity, to assess for myocardial ischemia if it will change management (Class IIb, Level of Evidence: B). Noninvasive stress testing is not recommended for low-risk surgery or for patients undergoing intermediate-risk surgery who have no cardiac risk factors (Class III, Level of Evidence: C). The type of stress test performed depends upon the individual patient and the data needed to provide optimal care. Below is a general guide for selecting the appropriate test.

Exercise treadmill test: If the patient can walk and the clinician is attempting to determine an estimate of functional capacity, assess stress-induced myocardial ischemia, and hemodynamic stability during stress, exercise ECG testing would be the test of choice. Low-risk patients will be able to perform a minimum of 4 METS without symptoms or ECG changes at 75% of maximum predicted heart rate. High-risk patients either develop symptoms of ischemia or have ECG evidence of ischemia at less than 75% of maximum predicted heart rate. Exercise ECG treadmill testing should not be used in those with abnormal baseline ECG as stress ECG changes will not be reliable for assessing myocardial ischemia.

Stress echocardiography: In patients in whom left ventricular function is in question or presence or severity of valvular disease is a concern, stress echocardiography provides reliable, cost-effective information. If the patient can walk, exercise echocardiography is preferable over dobutamine stress echocardiography in order to ascertain functional capacity.

For those who cannot walk or exercise, dobutamine stress echocardiography has been shown to be comparable to thallium stress testing for preoperative assessment and it provides reliable data regarding valvular function. Dobutamine echocardiography should be avoided in those with significant arrhythmias (including atrial arrhythmias with rapid ventricular response), severe hypertension, or known severe valvular disease.

Nuclear stress imaging has been shown to be effective for preoperative evaluation, particularly if the image quality from echocardiography is expected to be poor. In addition to providing information regarding stress-induced myocardial ischemia, nuclear stress imaging also provides data about left ventricular function and helps quantify and localize myocardial territory at risk. Only reversible defects have been correlated with perioperative events, with the presence of three of more reversible defects predicting the highest risk.

Coronary angiography prior to intermediate or high-risk noncardiac surgery is indicated in patients who are at high risk of hard cardiac events based on noninvasive stress testing, unstable angina, or angina unresponsive to medical therapy. These patients are at increased risk of perioperative events; however, revascularization prior to surgery has not been shown to improve mortality. It is also considered reasonable to pursue coronary angiography in patients scheduled for intermediate or high risk surgery who have equivocal noninvasive stress testing. Coronary angiography is not indicated prior to noncardiac surgery in patients with stable angina. Routine preoperative coronary angiography is also not recommended. (Class III, Level of Evidence: C)

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Depending on the acuity of the surgery, laboratory data may be limited and focused with a particular emphasis on electrolytes, renal function, hematocrit, platelet count, and coagulation markers. A more thorough laboratory evaluation may take place in the less acute setting if it will affect perioperative medical management, change current medical therapy, lead to a higher level of care intraoperatively or postoperatively, or change the timing or nature of the surgical procedure.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Routine radiologic imaging for perioperative risk assessment is not necessary. However, if decompensated heart failure is a concern, plain radiographs of the chest in both posterior-anterior and lateral projections can provide corroborating evidence of pulmonary vascular redistribution consistent with congestive heart failure.

III. Management.

Management of patient's with CAD undergoing noncardiac surgery falls into two categories: revascularization and medical therapy.

Coronary artery revascularization is considered a Class I indication in the following situations:

  1. Stable angina with significant left main artery disease (Level of Evidence: A).

  2. Stable angina with three-vessel CAD (Level of Evidence: A).

  3. Stable angina with two-vessel CAD with significant, proximal left anterior artery disease with either an ejection fraction <50% or demonstrable ischemia on noninvasive stress testing (Level of Evidence: A).

  4. Acute coronary syndromes (i.e., unstable angina, non-ST elevation MI, or ST-elevation MI) (Level of Evidence: A).

Coronary revascularization is not routinely indicated in patients with stable CAD (Class III, Level of Evidence: B). Elective noncardiac surgery is not recommend for 30 days following placement of a bare mental stent or 6 months following the placement of a drug-eluting stent as to not interrupt dual antiplatelet therapy (Class I, Level of Evidence: B). Elective noncardiac surgery after DES implantation in patients for whom P2Y12 inhibitor therapy will need to be discontinued may be considered after 3 months if the risk of further delay of surgery is greater than the expected risks of stent thrombosis (Class IIb, Level of Evidence: C). For patients who must undergo urgent noncardiac surgery who are taking dual antiplatelet therapy for stent placement, it is reasonable to discontinue the thienopyridine and continue aspirin. The thienopyridine should be restarted as soon as possible following surgery.

If patients do not meet the above criteria for revascularization, then optimal medical therapy with attention to beta-blockade and statins should be the focus of the clinician. Although the data is limited, both beta-blockade and statins may be beneficial for the patient undergoing noncardiac surgery to reduce the risk of ischemia, MI, and death in patients with established CAD.

Beta-blockade is considered a Class I indication for:

  1. Beta blockers should be continued in patients undergoing surgery who have been on beta blockers chronically (Class I, Level of Evidence: B).

Beta-blockade is considered a Class IIb indication for:

  1. In patients with intermediate- or high-risk myocardial ischemia noted in preoperative risk stratification tests, it may be reasonable to begin perioperative beta blockers. (Level of Evidence: C).

  2. In patients with 3 or more risk factors (e.g., diabetes mellitus, HF, CAD, renal insufficiency, cerebrovascular accident), it may be reasonable to begin beta blockers before surgery (Level of Evidence: B).

  3. In patients with a compelling long-term indication for beta-blocker therapy but no other risk factors, initiating beta blockers in the perioperative setting as an approach to reduce perioperative risk is of uncertain benefit (Level of Evidence: B).

Beta-blocker therapy should be used selectively as outlined above. Patients who are at low risk should not receive beta-blocker therapy. If initiating beta-blocker therapy, a long-acting beta blocker should be used preferentially over a short-acting beta blocker and should be started at least 1 week prior to surgery. Perioperative beta-blockade should be adjusted for blood pressure and heart rate. Beta-blocker therapy should not be started on the day of surgery (Class III, Level of Evidence: C).

Statin therapy is considered a Class I indication for:

  1. Patients taking statins and scheduled for noncardiac surgery (Level of Evidence: B).

Statin therapy is considered a Class IIa indication for:

  1. Patients undergoing vascular surgery with or without clinical risk factors (Level of Evidence: B).

Low-dose clonidine increased the rates of hypotension and nonfatal cardiac arrest after noncardiac surgery in the POISE-2 trial. Alpha-2 agonists for prevention of cardiac events are not currently recommended in patients who are undergoing noncardiac surgery (Class III, Level of Evidence: B).

Aspirin Therapy: The POISE-2 trial found that patients given aspirin after noncardiac surgery had a higher risk of major bleeding than the patients who did not receive aspirin. At the same time, aspirin did not reduce the incidence of postoperative MI or mortality. For patients undergoing noncardiac surgery and on chronic aspirin therapy, it appears that aspirin may increase bleeding without ischemic benefit. Stopping aspirin 3 or more days before surgery and restarting aspirin 8 to 10 days after surgery when the bleeding risk has diminished, would be a reasonable strategy for most individuals.

Important considerations for this trial were that patients with coronary stents represented only a small proportion of the total study cohort (<5%). Therefore, among such patients, the perioperative use of aspirin is still warranted. In patients treated with dual antiplatelet therapy after coronary stent implantation who must undergo surgical procedures that mandate the discontinuation of P2Y12 inhibitor therapy, it is recommended that aspirin be continued if possible (Class I, Level of Evidence: C).

A. Immediate management.

In the perioperative period, careful attention should be paid to ST segments on telemetry, as well as signs or symptoms of acute coronary syndromes. Changes in ST segments and/or unexpected arrhythmias seen on telemetry should prompt an immediate 12-lead ECG. Symptoms suggestive of cardiac ischemia should also prompt serial measurement of cardiac enzymes. In addition to beta-blockers, stains and tight control of blood pressure, postoperative pain should be controlled to lessen catecholaminergic surges, which may predispose the patient to acute ischemia.

B. Long-term management.

For patients undergoing noncardiac surgery, preoperative assessment and perioperative management may be the first comprehensive evaluation of the patient. As such, it should be used as an opportunity to provide optimal medical therapy and minimize long-term risk of cardiovascular disease.

As in-hospital initiation of medical therapy has been shown to increase compliance, ensuring patients are on appropriate medical therapy for their underlying CAD and comorbidities is essential for their long-term benefit. As with all known CAD patients, special attention should be paid to antiplatelet therapy, hypertension, lipids, blood glucose, and ventricular function.

Additionally, for patients who suffer from nonfatal MI, recurrent postoperative ischemic or ischemic heart failure, they incur a 2 to 3 fold increased risk of recurrent MI or death in the 4 years following surgery. Given this, their subsequent risk stratification and management should be aggressive.

What's the evidence for specific management and treatment recommendations?

Weiser, TG, Regenbogen, SE, Thompson, KD. "An estimation of the global volume of surgery: a modeling strategy based on available data". Lancet. vol. 372. 2008. pp. 139-44.

(Defines the prevalence of the topic.)

Fleisher, LA, Fleischmann, KE, Auerbach, AD. "2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines". Circulation. vol. 130. 2014. pp. e278-e333.

(Full text guidelines for the evaluation and management of the noncardiac surgery patient.)

Devereaux, PJ, Goldman, L, Cook, DJ. "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". CAMJ. vol. 173. 2005. pp. 627-34.

(Provides context for perioperative risk assessment.)

Reilly, DF, McNeely, MJ, Doerner, D. "Self-reported exercise tolerance and the risk of serious perioperative complications". Arch Intern Med. vol. 159. 1999. pp. 2185-92.

(Provides the context for evaluating the noncardiac surgery patient based on their functional capacity.)

Landesberg, G, Einav, S, Christopherson, R. "Perioperative ischemia and cardiac complications in major vascular surgery: importance of the preoperative twelve-lead electrocardiogram". J Vasc Surg. vol. 26. 1997. pp. 570-8.

(Provides context for patients that would benefit from preoperative ECG.)

Gibbons, RJ, Balady, GJ, Bricker, JT. "ACC/AHA 2002 guideline update for exercise testing: summary article. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1997 Exercise Testing Guidelines)". J Am Coll Cardiol. vol. 40. 2002. pp. 1531-40.

(Provides context for stress testing.)

Wilson, SH, Fasseas, P, Orford, JL. "Clinical outcome of patients undergoing noncardiac surgery in the two months following coronary artery stenting". J Am Coll Cardiol. vol. 42. 2003. pp. 234-40.

(Provides context for antiplatelet management in the perioperative period following DES placement.)

Lindenauer, PK, Pekow, P, Wang, K. "Perioperative beta blocker therapy and mortality after major noncardiac surgery". N Engl J Med. vol. 353. 2005. pp. 349-61.

(Provides context for use of beta-blockers perioperatively.)

Lindenauer, PK, Pekow, P, Wang, K. "Lipid-lower therapy and in-hospital mortality following major noncardiac surgery". JAMA. vol. 291. 2004. pp. 2092-9.

(Provides context for use of statins perioperatively.)

Levine, GN, Bates, ER, Bittl, JA. "2016 ACC/AHA guideline focused update on duration of dual antiplatelet therapy in patients with coronary artery disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines". J Am Coll Cardiol. vol. 68. 2016. pp. 1082-115.

(Provides context on timing of elective noncardiac surgery in patients treated with PCI and DAPT.)

Devereaux, PJ, Mrkobrada, M, Sessler, DI. "on behalf of the POISE-2 Investigators. Aspirin in patients undergoing noncardiac surgery". N Engl J Med. vol. 370. 2014. pp. 1494-503.

(Provides context on safety and efficacy aspirin noncardiac surgery.)

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