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Anesthesia and Noncardiac Surgery in Patients with Heart Disease
Additional content is available online at Elsevier eBooks for Practicing Clinicians
Cardiovascular morbidity and mortality represent a special concern in patients with known (or with risk factors for) cardiovascular disease who undergo noncardiac surgery. The cost of perioperative myocardial injury adds substantially to the total health care expenditure, with an average increased length of stay (LOS) of 6.8 days for patients with perioperative myocardial ischemic injury. Perioperative cardiovascular complications not only affect the immediate period but may also influence the outcome over subsequent years with an increased risk of readmission and death. The evidence base for managing patients with cardiovascular disease in the context of noncardiac surgery has grown in recent decades, beginning with identification of those at greatest risk and progressing to randomized trials to identify strategies for reducing perioperative cardiovascular complications. Guidelines provide information for the management of high-risk patients and disseminate best practices published by three major groups. Indeed, over the last decade, mortality rates for all major surgeries have decreased in parallel with implementation of these practices. This chapter distills this information by incorporating guidelines available from the American College of Cardiology and American Heart Association (ACC/AHA), the European Society of Cardiology (ESC), and the Canadian Cardiovascular Society (CCS). The ACC/AHA Guideline was updated in 2014 with a focused update on dual antiplatelet therapy in 2016.
Assessment of Risk
Numerous points of entry lead to evaluation of patients before they undergo noncardiac surgery. Primary physicians or cardiologists may encounter such patients. History and physical examination represent the cornerstone of surgical risk evaluation, but risk assessment testing is rarely performed unless changes in management will result. Many patients undergo evaluation just before surgery by the surgeon or anesthesiologist. Importantly, several cardiovascular conditions require assessment independent of the time before surgery.
Ischemic Heart Disease
The stress related to noncardiac surgery increases metabolic requirements and activates the sympathetic nervous system and may raise the heart rate (HR) preoperatively, which is associated with a high incidence of symptomatic and asymptomatic myocardial ischemia. Preoperative clinical evaluation of patients may therefore identify stable or unstable coronary artery disease (CAD). Patients with acute manifestations of CAD such as unstable angina or other cardiac disease like decompensated heart failure (HF) have a high risk for the development of further decompensation, myocardial infarction (MI), and death during the perioperative period. Such patients clearly warrant further evaluation and medical stabilization prior to surgery. If the noncardiac surgery is truly an emergency, several small older case series have shown that intra-aortic balloon pump counterpulsation can provide short-term myocardial protection beyond that afforded by maximal medical therapy, although this measure is seldom used today.
If the patient is clinically stable, identification of known asymptomatic or symptomatic stable CAD or risk factors for CAD can foster the implementation of guideline-based risk reduction therapies. There is currently no significant adjunctive therapy that ameliorates cardiovascular surgical risk. In determining the extent of preoperative evaluation, it is important not to perform testing unless the results will affect perioperative management. In addition, the use of medications or interventions should mirror those that would be implemented in the absence of surgery. Infrequently, these changes in management may include cancellation of surgery (if the risk-benefit ratio is prohibitive) and consideration of palliative therapy, delay of surgery for further medical management, coronary investigation and interventions before surgery, use of an intensive care unit (ICU), and changes in monitoring. As discussed later, few evidence-based therapies are available independent of treating the underlying atherosclerotic risk, and except in the case of left main coronary artery stenosis, current data challenge the benefit of preoperative coronary revascularization. Thus, the primary reason to perform risk assessment is to determine clinical cardiovascular instability and suitability for surgery.
Over the last two decades, there has been a secular decrease in the rates of perioperative type 1 MI and mortality. Finks and colleagues reported a 36% decrease in death after open abdominal aortic aneurysm repair from 2000 to 2008, to a risk-adjusted mortality of 2.8%. More recent data substantiate a decreasing frequency of type 1 MI and increasing rate of type 2 MI, indicating a predominance of subendocardial ischemic events resulting from hemodynamic challenge and more sensitive biomarker testing. Although these events are characterized by increases in troponin and are strongly associated with death, the interval between troponin elevation and adverse events and the higher rate of nonvascular than cardiovascular mortality suggest that this is a marker of illness rather than a mechanism of mortality.
Traditionally, assessment of the coronary risk associated with noncardiac surgery in patients with previous MI was based on the time between the MI and surgery. Multiple older studies have demonstrated an increased incidence of reinfarction after noncardiac surgery if the previous MI had occurred within 6 months of the operation. Improvements in MI management and perioperative care have shortened this interval. Although in some patients after a recent MI the myocardium may still be at risk for subsequent ischemia and infarction, most patients in the United States will have had critical coronary stenoses identified and revascularized when appropriate and should already be receiving maximal medical therapy. The AHA/ACC Task Force on Perioperative Evaluation of the Cardiac Patient Undergoing Noncardiac Surgery has suggested that the highest-risk patients are those within 30 days of MI, during which time plaque and myocardial healing occur. After this period, risk stratification is based on the features of the disease (i.e., those with active ischemia are at highest risk). It should be noted that a study using administrative data from California demonstrated that the rate of perioperative cardiac morbidity and mortality remained elevated for at least 60 days after an MI, and the current iteration of the guidelines supports such a time frame.
Hypertension
In the 1970s a series of case studies changed the prevailing thought that the use of antihypertensive agents should be discontinued before surgery. The reports suggested that poorly controlled hypertension was associated with untoward hemodynamic responses and that antihypertensives should be continued perioperatively. However, several large prospective studies were unable to establish mild to moderate hypertension as an independent predictor of postoperative cardiac complications including cardiac death, postoperative MI, HF, or arrhythmias. The approach to patients with hypertension therefore relies mostly on management strategies from the nonsurgical literature.
Blood pressure (BP) excursions in the operative and postoperative period portend worsening outcome. A hypertensive crisis in the postoperative period—defined as diastolic BP higher than 120 mm Hg and clinical evidence of impending or actual end-organ damage—poses a definite risk for MI and cerebrovascular accident (CVA, stroke). Iatrogenic precipitants of hypertensive crises include abrupt withdrawal of clonidine or beta blocker therapy before surgery, chronic use of monoamine oxidase inhibitors with or without sympathomimetic drugs, and inadvertent discontinuation of antihypertensive therapy. Similarly, intraoperative hypotension is associated with both type 2 MI and increases in postoperative mortality.
Although postulated to predict an increased rate of myocardial ischemia, none of the recent large clinical trials has shown that chronic hypertension predisposes patients to perioperative cardiovascular events. This finding likely reflects, in part, the excellent perioperative management of hypertension in the current era. The pharmacologic management of patients with hypertension should be continued perioperatively, and BP should be maintained near preoperative levels to reduce the risk for myocardial ischemia. In patients with more severe hypertension, such as a diastolic BP higher than 110 mm Hg, little evidence suggests a benefit of delaying surgery to optimize antihypertensive medications in the absence of a hypertensive urgency or emergency. Currently, debate surrounds the optimal decision on withholding angiotensin-converting enzyme inhibitors and angiotensin receptor blockers on the day of surgery to avoid intraoperative hypotension. Studies support both continuation and withholding, although continuation may require treatment with vasopressin for intractable hypotension. It is important to restart these agents as soon as possible postoperatively.
The importance of perioperative BP management was studied in the Intraoperative Norepinephrine to Control Arterial Pressure (INPRESS) study, a multicenter, randomized, clinical trial of an individualized management strategy aimed at achieving a systolic BP within 10% of the reference value (i.e., patient’s resting systolic BP) or standard management strategy of treating systolic BP less than 80 mm Hg or lower than 40% from the reference value during and for 4 hours following surgery. Among 292 patients who completed the trial, management targeting an individualized systolic BP, compared with standard management, reduced the risk of postoperative organ dysfunction.
Heart Failure
HF is associated with perioperative cardiac morbidity after noncardiac surgery in virtually all studies. Since the early work of Goldman and colleagues, who identified signs of HF as a significant risk of adverse perioperative events, HF has become more common with more varied presentations, including the presence or absence of ischemia and of reduced left ventricular ejection fraction. The underlying causes in patients with signs or symptoms of HF who are scheduled for noncardiac surgery require characterization. HF may eclipse CAD as a cause of postoperative adverse events. The 30-day postoperative mortality rate was significantly higher in patients with both nonischemic (9.3%) and ischemic (9.2%) HF compared to those with CAD (2.9%) in a population-based data analysis of 38,047 consecutive patients.
The preoperative evaluation should aim to identify the underlying coronary, myocardial, and valvular heart disease and assess the severity of the systolic and diastolic dysfunction. Hammill and associates used Medicare claims data to evaluate short-term outcomes in patients with HF, CAD, or neither who underwent major noncardiac surgery. Elderly patients with HF who underwent major surgical procedures had substantially higher risk for operative mortality and hospital readmission than other patients, including those with CAD, admitted for the same procedures. A study using the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database demonstrated that worsening preoperative HF is associated with a significant increase in postoperative morbidity and mortality when controlling for other comorbidities. In the absence of a surgical emergency, patients with decompensated HF should be treated to achieve a euvolemic, stable state before operation. Ischemic cardiomyopathy is of greatest concern because the patient has the additional substantial risk for the development of further ischemia, which can lead to myocardial necrosis and potentially induce a downward spiral.
Hypertrophic Cardiomyopathy
Treatment of decompensated hypertrophic cardiomyopathy differs from that of dilated cardiomyopathy, and thus the preoperative evaluation can influence perioperative management in this setting (see Chapter 54 ). In particular, this assessment may influence perioperative fluid and vasopressor management. Obstructive hypertrophic cardiomyopathy was formerly regarded as a high-risk condition associated with high perioperative morbidity. A retrospective review of perioperative care in 35 patients, however, suggested low risk related to general anesthesia and major noncardiac surgery in such patients. This study also suggested that spinal anesthesia was a relative contraindication in view of the sensitivity of cardiac output to preload in this condition. Haering and colleagues studied 77 patients with asymmetric septal hypertrophy identified retrospectively from a large database; 40% had one or more adverse perioperative cardiac events, including one patient with MI and ventricular tachycardia who required emergency cardioversion. Most of the events consisted of perioperative congestive HF, and no perioperative deaths occurred. Unlike the finding in the original cohort of patients, the type of anesthesia was not an independent risk factor. Important independent risk factors for an adverse outcome (as seen generally) included major surgery and increasing duration of surgery.
Valvular Heart Disease
Aortic stenosis places patients at increased risk. Critical stenosis is associated with the highest risk for cardiac decompensation in patients undergoing elective noncardiac surgery (see Chapter 72 ). Thus, the presence of any of the classic triad of angina, syncope, and HF in a patient with aortic stenosis should prompt further evaluation and potential interventions (usually valve replacement). Preoperative patients with aortic systolic murmurs warrant a careful history and physical examination—and often further evaluation. Several recent case series of patients with critical aortic stenosis have demonstrated that when necessary, noncardiac surgery can be performed with acceptable risk. In a matched-sample study using the Danish Health Care System, Andersson and colleagues demonstrated that patients with asymptomatic aortic stenosis did not experience a higher rate of major adverse cardiovascular events (MACE) or mortality in elective surgery. Emergency surgery type and symptomatic aortic stenosis increased both MACE and mortality. Aortic valvuloplasty is a bridging option for selected patients who cannot undergo valve replacement or percutaneous intervention in the short term. The substantial risk for procedure-related morbidity and mortality and little evidence to demonstrate a perioperative risk reduction mandate careful consideration before recommending this strategy. ,
Mitral valve disease is associated with a lower risk for perioperative complications than aortic stenosis, although occult rheumatic mitral stenosis can sometimes lead to severe left-sided HF in patients with tachycardia (e.g., uncontrolled atrial fibrillation [AF]) and volume loading (see Chapter 75 ). In contrast to aortic valvuloplasty, mitral valve balloon valvuloplasty often yields both short- and long-term benefit, especially in younger patients with predominant mitral stenosis but without severe mitral valve leaflet thickening or significant subvalvular fibrosis and calcification.
In perioperative patients with a functioning prosthetic heart valve, antibiotic prophylaxis and anticoagulation require management (see Chapter 79 ). All patients with prosthetic valves who undergo procedures that can cause transient bacteremia should receive prophylaxis. In patients with prosthetic valves, the risk for increased bleeding during a procedure while receiving antithrombotic therapy must be weighed against the increased risk for thromboembolism caused by stopping the therapy. Common practice in patients undergoing noncardiac surgery with a mechanical prosthetic valve in place is cessation of warfarin 3 days before surgery. This allows the international normalized ratio (INR) to fall to less than 1.5 times normal; oral anticoagulants can then be resumed on postoperative day 1. A multicenter, single-arm cohort study of 224 high-risk patients (prosthetic valves, AF, and a major risk factor) investigated the use of low-molecular-weight heparin (LMWH) as a preoperative bridge to warfarin anticoagulation in which warfarin was withheld for 5 days and LMWH was given 3 days preoperatively and at least 4 days postoperatively. The overall rate of thromboembolism was 3.6% and of cardioembolism 0.9%. Major bleeding was seen in 6.7% of patients, although only 8 of 15 episodes occurred during the administration of LMWH. LMWH is cost-effective because it helps reduce the duration of the hospital stay, but two studies have shown a residual anticoagulation effect in as many as two thirds of patients.
Many current prosthetic valves have a lower risk for valve thrombosis than the older designs, so the risk associated with heparin may outweigh its benefit in the perioperative setting. According to the 2020 AHA/ACC guidelines on management of valvular heart disease, heparin can usually be reserved for high-risk patients. High risk is defined by the presence of a mechanical mitral or tricuspid valve or a mechanical aortic valve in the presence of certain risk factors, including AF, previous thromboembolism, hypercoagulable condition, older-generation mechanical valves, an ejection fraction lower than 30%, or more than one mechanical valve. Bridging anticoagulation therapy with heparin during the preoperative time interval when the INR is subtherapeutic should be made on an individualized basis, with the risks of bleeding weighed against the benefits of thromboembolism prevention. Subcutaneous LMWH or unfractionated heparin offers an alternative outpatient approach but has received only a tentative recommendation. Discussion between the surgeon and cardiologist regarding optimal perioperative management is critical. The 2020 ACC/AHA guidelines also note that it is reasonable to consider the need for bridging anticoagulant therapy around the time of invasive procedures in patients with bioprosthetic heart valves or annuloplasty rings who are receiving anticoagulation for AF on the basis of the CHA2DS2-VASc score weighed against the risk of bleeding.
Congenital Heart Disease in Adults (See Also Chapter 82 )
Congenital heart disease afflicts 500,000 to 1 million adults in the United States. The nature of both the underlying anatomy and any anatomic correction affects the perioperative plan and incidence of complications, which include infection, bleeding, hypoxemia, hypotension, and paradoxical embolization. In a study using the NSQIP database, prior cardiac surgery in a population age 19 to 39 years significantly increased the risk of death, MI, stroke, reoperation, and LOS. Pulmonary hypertension and Eisenmenger syndrome present a major concern in patients with congenital heart disease. Regional anesthesia has traditionally been avoided in these patients because of the potential for sympathetic blockade and worsening of the right-to-left shunt. However, a review of 103 cases found that overall perioperative mortality was 14%; patients receiving regional anesthesia had a mortality of 5%, whereas those receiving general anesthesia had a mortality of 18%. The authors concluded that most deaths probably resulted from the surgical procedure and the disease rather than from anesthesia. Although perioperative and peripartum mortality was high, many anesthetic agents and techniques have been used with success. Patients with congenital heart disease are at risk for infective endocarditis and should receive antibiotic prophylaxis (see Chapter 82 ).
Arrhythmias
Cardiac arrhythmias frequently occur in the perioperative period, particularly in older adults or patients undergoing thoracic surgery. Predisposing factors include previous arrhythmias, underlying heart disease, hypertension, perioperative pain (e.g., hip fractures), severe anxiety, and other situations that heighten adrenergic tone. In a prospective study of 4181 patients 50 years or older, supraventricular arrhythmia occurred in 2% during surgery and in 6.1% after surgery. Perioperative AF raises several concerns, including the incidence of stroke (see Chapter 45, Chapter 66 ). In a study of 317 patients without AF undergoing major vascular surgery reported by Winkle et al. (see “Classic References”), the incidence of new-onset AF was 4.7% and was associated with more than a sixfold increase in cardiovascular death, MI, unstable angina, and stroke in the first 30 days and a fourfold increase over the next 12 months. Early treatment to restore sinus rhythm or control the ventricular response and initiate anticoagulation may be indicated. Prophylactic use of intravenous (IV) diltiazem and esmolol in randomized, placebo-controlled trials of patients undergoing high-risk thoracic surgery reduced the incidence of clinically significant atrial arrhythmias.
Although older studies identified ventricular arrhythmias as a risk factor for perioperative morbidity, recent studies have not confirmed this finding. Current guidelines cite studies of patients undergoing major noncardiac surgical procedures reporting that preoperative arrhythmias are associated with intraoperative and postoperative arrhythmias, but not with nonfatal MI and cardiac death. However, this remains controversial as a population-based study by van Diepen et al. reported that the risk of mortality at 30 days was 6.4% in patients with preoperative AF compared with 2.9% for patients with CAD (see “Classic References”). These findings suggest that a preoperative arrhythmia should provoke a search for underlying cardiopulmonary disease, ongoing myocardial ischemia or infarction, drug toxicity, or electrolyte or metabolic derangements as suggested by other clinical circumstances.
Conduction abnormalities can increase perioperative risk and may require placement of a temporary or permanent pacemaker. On the other hand, patients with intraventricular conduction delays, even in the presence of a left or right bundle branch block but without a history of advanced heart block or symptoms, rarely progress to complete heart block perioperatively. The availability of transthoracic pacing units has decreased the need for temporary transvenous pacemakers.
The Decision to Undergo Diagnostic Testing
The ACC/AHA and ESC proposed algorithms for CAD evaluation based on the available evidence and incorporated the class of recommendations and level of evidence into each step ( Figs. 23.1 and 23.2 ). Current algorithms use a stepwise Bayesian strategy that relies on assessment of clinical markers, previous coronary evaluation and treatment, functional capacity, and surgery-specific risk. Successful use of the ACC/AHA algorithm requires an appreciation of the different levels of risk attributable to the combination of clinical circumstances and type of surgery, levels of functional capacity, and how the information from any diagnostic testing will influence perioperative management.
Multiple studies have attempted to identify clinical risk markers for perioperative cardiovascular morbidity and mortality. As described earlier, patients with unstable coronary syndromes and severe valvular disease have active cardiac conditions. Risk can be divided into low (<1%) and elevated clinical risk. The 2014 ACC/AHA guidelines advocate using a risk index. This includes either the ACS NSQIP risk calculator or myocardial infarction and cardiac arrest (MICA) risk calculator, which incorporates both surgical and clinical risk. Alternatively, the clinician can incorporate the revised cardiac risk index (RCRI) with the estimated surgical risk to differentiate low from elevated risk ( Table 23.1 ). Cardiovascular disease also has clinical risk markers classified as “low-risk factors,” each of which is associated with variable levels of perioperative risk. Recent investigation of more than 3 million patients using the United States National Surgical Quality Improvement Program shows patients without hypertension, diabetes mellitus, or current smoking have a postoperative MI and death rate of 0.1% and 0.47%, respectively. The previous classification of perioperative, active clinical risk markers to assess the need for further testing includes issues beyond ischemic heart disease ( Table 23.2 ).
TABLE 23.1
Cardiac Risk ∗ Stratification for Noncardiac Surgical Procedures
From 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. J Am Coll Cardiol . 2009;54:e77–e137.
| Risk Stratification | Examples of Procedures |
|---|---|
| High (reported cardiac risk often >5%) | Aortic and other major vascular surgery Peripheral vascular surgery |
| Intermediate (reported cardiac risk generally 1%–5%) | Intraperitoneal and intrathoracic surgery Carotid endarterectomy Head and neck surgery Orthopedic surgery Prostate surgery |
| Low † (reported cardiac risk generally <1%) | Endoscopic procedures Superficial procedure Cataract surgery Breast surgery Ambulatory surgery |
∗ Combined incidence of cardiac death and nonfatal myocardial infarction.
† These procedures do not generally require further preoperative cardiac testing.
TABLE 23.2
Active Cardiac Conditions for Which Patients Should Undergo Evaluation and Treatment Before Noncardiac Surgery (Class I; Level of Evidence: B)
From 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. J Am Coll Cardiol . 2009;54(22):e77–e137.
| Condition | Examples |
|---|---|
| Unstable coronary syndromes | Unstable or severe angina ∗ (CCS class III or IV) † Recent myocardial infarction (MI) ‡ |
| Decompensated HF (NYHA functional class IV; worsening or new-onset HF) | |
| Significant arrhythmias | High-grade atrioventricular block Mobitz II atrioventricular block Third-degree atrioventricular heart block Symptomatic ventricular arrhythmias Supraventricular arrhythmias (including atrial fibrillation) with an uncontrolled ventricular rate (heart rate >100 beats/min at rest) Symptomatic bradycardia Newly recognized ventricular tachycardia |
| Severe valvular disease | Severe aortic stenosis (mean pressure gradient >40 mm Hg, aortic valve area <1.0 cm 2 , or symptomatic) Symptomatic mitral stenosis (progressive dyspnea on exertion, exertional presyncope, or HF) |
CCS, Canadian Cardiovascular Society; HF, heart failure; NYHA, New York Heart Association.
∗ According to Campeau L, Enjalbert M, Lespérance J, et al. Atherosclerosis and late closure of aortocoronary saphenous vein grafts: sequential angiographic studies at 2 weeks, 1 year, 5 to 7 years, and 10 to 12 years after surgery. Circulation . 1983;68(Suppl II):1–7.
† May include “stable” angina in patients who are unusually sedentary.
‡ The American College of Cardiology National Database Library defines “recent” MI as more than 7 days but 1 month or less (within 30 days) although the 2014 guidelines suggest 60 days.
Exercise tolerance is one of the strongest determinants of perioperative risk and the need for invasive monitoring. Several scales based on activities of daily living have been proposed to assess exercise tolerance; current guidelines advocate the Duke Activity Scale Index ( Table 23.3 ).
TABLE 23.3
Estimated Energy Requirements for Various Activities
Modified from Hlatky MA, Boineau RE, Higginbotham MB, et al. A brief self-administered questionnaire to determine functional capacity (the Duke Activity Status Index). Am J Cardiol . 1989;64:651–654; and 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. J Am Coll Cardiol . 2009;54:e77–e137.
| Can You … | |
|---|---|
| 1 MET | Take care of yourself? Eat, dress, or use the toilet? Walk indoors around the house? Walk a block or two on level ground at 2–3 mph (3.2–4.8 kph)? |
| 4 METs | Do light work around the house such as dusting or washing dishes? Climb a flight of stairs or walk up a hill? Walk on level ground at 4 mph (6.4 kph)? Run a short distance? Do heavy work around the house such as scrubbing floors or lifting or moving heavy furniture? Participate in moderate recreational activities such as golf, bowling, dancing, doubles tennis, or throwing a baseball or football? |
| >10 METs | Participate in strenuous sports such as swimming, singles tennis, football, basketball, or skiing? |
MET, Metabolic equivalent; mph, miles per hour; kph, kilometers per hour.
The type of surgical procedure significantly impacts perioperative risk and the amount of preparation required to perform anesthesia safely. For surgical procedures not associated with significant stress or a high incidence of perioperative myocardial ischemia or morbidity, the cost and procedural delay of the evaluation often exceed any benefit from the information gained by preoperative assessment. Outpatient procedures, for example, cause minimal morbidity and mortality; in such patients, cardiovascular status rarely changes perioperative management unless the patient has unstable angina or overt HF. In fact, 30-day mortality after outpatient surgery may actually be lower than that expected if the patient did not undergo surgery. In contrast, open surgery for vascular disease entails a high risk for morbidity and the potential for ischemia. Intra-abdominal, thoracic, and orthopedic procedures are associated with elevated risk, which, when combined with clinical risk factors, determine overall perioperative risk. Endovascular procedures fall into this intermediate-risk category because of their associated perioperative morbidity and mortality, although long-term survival appears to be similar to that in patients who undergo open procedures.
In addition to the risk related to the surgical procedure itself, risk is also correlated with the surgical volume in a given center. Several studies have demonstrated differential mortality rates in both cancer and vascular surgery, with higher mortality occurring in low-volume centers, although recent studies have demonstrated that low-volume centers may also have low mortality rates if proper care systems are in place. Surgical mortality rates may therefore be institution specific, which may influence the decision to perform further perioperative evaluations and interventions.
Risk Calculators
Much of the contemporary study of perioperative cardiac risk has focused on the development of clinical risk indices. The most widely used index was developed in a study of 4315 patients age 50 or older undergoing elective major noncardiac procedures in a tertiary care teaching hospital. The index includes six independent predictors of complications in a revised cardiac risk index : high-risk type of surgery, history of ischemic heart disease, history of congestive HF, history of cerebrovascular disease, preoperative treatment with insulin, and preoperative serum creatinine concentration greater than 2.0 mg/dL. Cardiac complication rates rise with an increasing number of these risk factors. Patients are stratified into low, intermediate, or high cardiovascular risk on the basis of having 0, 1 or 2, or 3 or more factors included in the RCRI, respectively. The RCRI has become a standard tool for assessing the probability of perioperative cardiac risk in a given individual and serves to direct the decision to perform cardiovascular testing and implement perioperative management protocols. The RCRI has undergone validation in vascular surgery populations and serves to predict long-term outcome and quality of life, although one group has advocated inclusion of age as a risk factor and its outcomes are derived from data a quarter century old.
Additional risk indices were developed from the ACS-NSQIP database. Gupta and colleagues developed a risk calculator for predicting perioperative myocardial infarction and cardiac arrest (see “Classic References”) in a study of 211,410 patients, of whom perioperative MI or cardiac arrest developed in 1371 (0.65%). Multivariate logistic regression analysis identified five predictors of perioperative MI or cardiac arrest: type of surgery, dependent functional status, abnormal creatinine level, American Society of Anesthesiologists class, and increasing age.
A universal risk calculator developed to predict multiple outcomes was based on 1,414,006 patients encompassing 1557 unique surgical procedure codes, which had excellent performance for mortality (C-statistic = 0.944) and morbidity (C-statistic = 0.816). Morbidity is defined as any of the following intraoperative or postoperative events: surgical site infection, wound disruption, pneumonia, unplanned intubation, pulmonary embolism, on ventilator greater than 48 hours, progressive renal insufficiency, acute renal failure, urinary tract infection, stroke/CVA, cardiac arrest, MI, deep venous thrombosis, (systemic sepsis), pneumonia, cardiac event (cardiac arrest or MI), SSI, UTI, VTE, and renal failure (progressive renal insufficiency or acute renal failure) ( http://riskcalculator.facs.org ). The risk calculator incorporates 21 preoperative risk factors and therefore has more discriminative ability than the MICA-specific risk calculator. Glance and colleagues demonstrated variability in the predicted risk of cardiac complications using different risk-prediction tools, also suggesting that the ACS-NSQIP risk calculator is the best option.
In 2019 American University of Beirut-Pre-Operative Cardiovascular Evaluation Study (AUB-POCES) prospectively derived and validated a new preoperative cardiovascular risk index (CVRI). It was subsequently renamed the AUB-HAS2 based on the six predictors of risk identified by multivariate logistic regression analysis in the derivation cohort: history of H eart disease, H eart symptoms of angina or dyspnea, A ge ≥75 years, A nemia with hemoglobin less than 12 mg/dL, vascular S urgery, and emergency S urgery. Patients were assigned a score of 0, 1, 2, 3, and greater than 3 based on the number of predictors. The incidence of the primary outcome of death, MI, or stroke at 30 days increased steadily across the increasing scores. A subsequent analysis of the performance of AUB-HAS2 in 9 surgical specialty groups and 8 site-specific surgeries using 1,167,278 noncardiac surgeries from the NSQIP database demonstrated superior discriminatory power compared with the RCRI. The performance of the AUB-HAS2 index was superior to that of the RCRI in all surgical subgroups ( P < 0.001) but needs further evaluation.
The Guidelines Approach
The ACC/AHA Task Force for Guidelines for Perioperative Cardiovascular Evaluation and Management for Noncardiac Surgery presented their recommendations in algorithmic form as a framework for determining which patients are candidates for cardiac testing (see Fig. 23.1 ). Given the availability of the evidence, the writing committee included the level of the recommendations and strength of evidence for each of the pathways. The current algorithm focuses exclusively on the evaluation for CAD. Valvular or other forms of heart disease are not included in the current algorithm.
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Step 1: The consultant should determine the urgency of performing noncardiac surgery. In many cases, patient- or surgery-specific factors dictate an obvious strategy (e.g., emergency surgery) that may not allow further cardiac assessment or treatment.
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Step 2: Does the patient have an acute coronary syndrome? Acute coronary syndromes include previous MI with evidence of substantial ischemic risk as determined by clinical symptoms or noninvasive study, unstable or severe angina, and new or poorly controlled ischemia-mediated HF. Depending on the results of tests or interventions and the risk inherent in delaying surgery, it may be appropriate to proceed to the planned surgery with maximal medical therapy.
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Step 3: What is the estimated perioperative risk of a MACE based on the combined clinical and surgical risk? The use of a validated risk index is advocated, either of the ACS-NSQIP risk indices or combining the RCRI with the estimated surgical risk.
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Step 4: Does the patient have low perioperative risk (<1%)? In such cases, no further testing is required.
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Step 5: Does the patient have elevated risk? Such circumstances merit assessment of functional capacity. If the patient has at least moderate exercise capacity (≥4 metabolic equivalents), management rarely changes on the basis of the results of any further cardiovascular testing, and it is therefore appropriate to proceed with the planned surgery. The strength of the evidence and the recommendation depends on the degree of exercise capacity, with excellent capacity having stronger evidence and recommendation. In the recently published METS study, subjectively assessed functional capacity should not be used for preoperative risk evaluation. The authors suggested that clinicians could instead consider a standardized measure such as Duke Activity Status Index (DASI) for cardiac risk assessment.
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Step 6: In patients with poor (<4 METs) or unknown functional capacity, the physicians and patient should jointly determine if further testing will impact decision making or perioperative care. If not, proceeding to surgery with goal-directed medical therapy is appropriate. In the current guidelines, the identification of elevated risk with poor functional capacity may also lead to the decision to proceed with alternative strategies, such as noninvasive treatment or palliation.
The CCS Guidelines use an entirely different approach and include the RCRI combined with the Brain Natriuretic Peptide (BNP) or NT-proBNP for risk assessment for more extensive postoperative monitoring as opposed to advocating preoperative cardiovascular testing. There is no management strategy to mitigate risk discussed after testing.
Tests to Improve Identification and Definition of Cardiovascular Disease
The use of testing to identify patients at high cardiovascular risk requires the acknowledgement of several secular outcome changes over time. First, overall results from surgery are excellent, with mortality rates for all patients hovering around 1% in all comers and continual improvement in higher-risk surgery. Second, type 1 MI requiring postoperative revascularization is uncommon. In a recent large, randomized trial of patients at high risk on the basis of an elevated troponin postoperatively requirement for study entry, fewer than 4% of this group underwent coronary revascularization. Indeed, mortality in recent trials is driven more by non-vascular events than vascular ones. From these data, we recommend the focus of testing remain actionable management changes, either providing a target for risk remediation or cancelling of surgery.
Several noninvasive diagnostic methods can diagnose and indicate the extent of CAD before noncardiac surgery. The exercise electrocardiogram (ECG) has traditionally served as an initial evaluation for the presence of CAD. As noted earlier, patients with excellent exercise tolerance in daily life will rarely benefit from further testing. Patients with poor exercise capacity, in contrast, may not achieve an adequate HR and BP for diagnostic purposes on electrocardiographic stress tests. Such patients often require concomitant imaging. Recent work demonstrates the common inappropriate use and lack of predictive value of stress testing in patients undergoing low risk surgery. Among more than 800,000 patients undergoing total hip or knee arthroplasty, half had a low-risk RCRI score of 0 and stress test acquisition resulted in no difference in the primary outcome of MI or cardiac arrest among patients with an RCRI score of ≥1.
Many high-risk patients either cannot exercise or have limitations to exercise (e.g., patients with intermittent claudication or knee arthritis). Pharmacologic stress testing, therefore, has become popular, particularly as a preoperative test in patients undergoing vascular surgery. Several studies have shown that the presence of a redistribution defect on dipyridamole or adenosine thallium or sestamibi imaging in patients undergoing peripheral vascular surgery predicts an increased risk for postoperative cardiac events (see Chapter 18 ). Pharmacologic stress imaging is best used in patients at moderate clinical risk. Several strategies may increase the predictive value of such tests. The redistribution defect can be quantitated, with larger areas of defect associated with increased risk. Additionally, either increased lung uptake or dilation of the left ventricular cavity indicate ventricular dysfunction with ischemia. Several investigative groups have demonstrated that delineation of low-risk and high-risk myocardial perfusion scans (larger area of defect, increased lung uptake, and dilation of the left ventricular cavity) greatly improves the test’s predictive value. Patients with high-risk scans have a particularly increased risk for perioperative morbidity and long-term mortality.
Stress echocardiography has also been used widely as a preoperative test (see Chapter 16 ). One advantage of this test is that it dynamically assesses myocardial ischemia in response to increased inotropy and HR, stimuli relevant to the perioperative period. The presence of new wall motion abnormalities occurring at a low HR is the best predictor of increased perioperative risk, with large areas of contractile dysfunction having secondary importance. As part of the DECREASE studies, Boersma and colleagues (as cited in the guidelines) assessed the value of dobutamine stress echocardiography with respect to the extent of wall motion abnormalities and the ability of preoperative treatment with beta blockers to attenuate risk in patients undergoing major aortic surgery. They assigned 1 point for each of the following characteristics: age older than 70 years, current angina, MI, congestive HF, previous cerebrovascular disease, diabetes mellitus, and renal failure. As the total number of clinical risk factors increases, perioperative cardiac event rates also increase. Furthermore, with a high-risk score, abnormal findings on an echocardiogram predict higher risk.
Several groups have published meta-analyses examining various preoperative diagnostic tests. Such studies report good predictive values for ambulatory electrocardiographic monitoring, radionuclide angiography, dipyridamole-thallium imaging, and dobutamine stress echocardiography. Shaw and colleagues also demonstrated excellent predictive values for dipyridamole thallium imaging and dobutamine stress echocardiography. Beattie and colleagues performed a meta-analysis of 25 stress echocardiography studies and 50 thallium imaging studies. The likelihood ratio for stress echocardiography was more indicative of a postoperative cardiac event than that for thallium imaging (likelihood ratio), 4.09; (95% confidence interval (CI), 3.21 to 6.56; versus LR, 1.83; 95% CI, 1.59 to 2.10; P < 0.001). The difference was attributable to fewer false-negative stress echocardiograms. A moderate to large abnormality found by either test predicted a greater risk of postoperative MI and death.
Institutional expertise should guide the choice of preoperative testing. The relevant clinical questions also influence the choice of test. For example, if valve function or ventricular wall thickness is of interest, echocardiography has advantages over perfusion imaging. Stress nuclear imaging may have slightly higher sensitivity, but stress echocardiography may have fewer false-positive results. The role of newer imaging modalities such as magnetic resonance imaging, multislice computed tomography, coronary calcium scores, and positron emission tomography in preoperative risk assessment is rapidly evolving.
Over the past decade, cardiopulmonary exercise testing (CPET) has been used as a preoperative test (see Chapter 15 ), particularly in Great Britain. A consistent finding of the studies was that a low anaerobic threshold was predictive of perioperative cardiovascular complications, postoperative death, or midterm and late death after surgery. An anaerobic threshold of approximately 10 mL O 2 /kg/min was proposed as the optimal discrimination point, with a range in these studies of 9.9 to 11 mL O 2 /kg/min. The METS study was designed to address the value of subjective assessment of exercise capacity, the objective Duke Activity Specific Index (DASI) questionnaire and a biomarker N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) to predict death or complications after major elective non-cardiac surgery. The investigators documented the poor discriminative ability of anesthesiologists to subjectively predict functional capacity; however, the DASI was predictive of myocardial injury and death. Although CPET did not have increased predictive ability for cardiac events, some of the measured variables were predictive of complications after surgery. CPET is therefore currently under evaluation as a means of determining both the need for and value of “prehabilitation,” in which a strategy of exercise is initiated to increase aerobic capacity before surgery. Several groups are studying the value of CPET to inform shared decision making in determining the appropriateness of surgery given the intermediate- and long-term outcomes in high-risk patients.
The use of biomarkers in risk stratification before surgery has also been investigated. A meta-analysis of 18 studies demonstrated that preoperative BNP measurement independently predicted perioperative cardiovascular events in studies that considered only the outcomes of death, or nonfatal MI (odds ratio [OR], 1.9; 95% CI, 1.38 to 2.58). In a large substudy of the Vascular Events in Noncardiac Surgery Cohort Evaluation (VISION) trial of more than 10,400 patients, higher preoperative levels of NT-proBNP associated directly with higher levels of cardiovascular events. In a stepwise pattern, the 30-day risk of vascular mortality increased from 0.2% in subjects with a NT-proBNP of less than 100 g/mL and increased directly with increasing NT-proBNP to 2.1% in patients with NT-proBNP ≥ 1500 pg/mL (HR 6.8 compared to referent). Thirty-day all-cause mortality increased with the previous thresholds from 0.3% to 3.4% (HR 8.4 compared to referent). Similar to exercise and imaging testing above, the lack of a management algorithm after abnormal measurement limits the ability of the clinician to modify surgical risk based on this test. Maile and coworkers reviewed 6030 patients with troponin measured in the 30 days before nonemergent noncardiac surgery and found a 30-day mortality of 4.7% in the group without detectable troponin levels, but a 12.7% mortality in the group with the highest tercile of troponin elevation. The closer in time that an elevated troponin was drawn to the date of surgery, the higher the risk.
Overview of Anesthesia for Cardiac Patients Undergoing Noncardiac Surgery
Three classes of anesthetics exist: general, regional, and local/sedation or monitored anesthesia care (MAC). General anesthesia can be defined best as a state that includes unconsciousness, amnesia, analgesia, immobility, and attenuation of autonomic responses to noxious stimulation, and it can be achieved with inhalational agents, IV agents, or a combination of these (frequently called a “balanced technique”). Contemporary general anesthesia does not always require an endotracheal tube. Laryngoscopy and intubation were traditionally considered the time of greatest stress and risk for myocardial ischemia, but extubation may actually engender even greater risk. Alternative methods for delivering general anesthesia include the use of a mask or a laryngeal mask airway—a device that fits above the epiglottis and does not require laryngoscopy or intubation.
Five inhalational anesthetic agents (in addition to nitrous oxide) are currently approved in the United States, although enflurane and halothane are rarely used today. All inhalational agents have reversible myocardial depressant effects and lead to decreases in myocardial oxygen demand. The degree to which they depress cardiac output depends on their concentration, their effects on systemic vascular resistance, and their effects on baroreceptor responsiveness; agents therefore differ in their specific effects on HR and BP. Isoflurane causes negative inotropic effects and potent vascular smooth muscle relaxation and has minimal effects on baroreceptor function. Desflurane has the fastest onset and is commonly used in the outpatient setting. The onset and offset of action of sevoflurane are intermediate to those of isoflurane and desflurane; the major advantage of sevoflurane is an extremely pleasant smell, which makes it the agent of choice in children.
Issues have arisen regarding the safety of inhalational agents in patients with CAD. Several large-scale, randomized and nonrandomized studies of patients undergoing coronary artery bypass grafting (CABG), however, demonstrated no increased incidence of myocardial ischemia or infarction in patients receiving inhalational agents versus narcotic-based techniques. The use of inhalational anesthetics in patients with CAD also has theoretical advantages. Several investigative groups demonstrated in vitro and in animals that inhalational agents have protective effects on myocardium similar to ischemic preconditioning, although the clinical relevance of this remains unclear.
High-dose narcotic techniques offer the advantages of hemodynamic stability and lack of myocardial depression. Narcotic-based anesthetics were frequently considered the “cardiac anesthesia” and were advocated for use in all high-risk patients, including those undergoing noncardiac surgery. The disadvantage of these traditional high-dose narcotic techniques is the requirement for postoperative ventilation. The ultrashort-acting narcotic remifentanil obviates the need for prolonged ventilation but provides hemodynamic stability. This agent can assist in early extubation of patients undergoing cardiac surgery and may aid in managing short periods of intense intraoperative stress in high-risk patients.
Despite the theoretical advantages of a high-dose narcotic technique, large-scale trials in patients undergoing CABG showed no difference in survival or major morbidity compared to the inhalation-based technique. This observation has contributed to the abandonment of high-dose narcotics in much of cardiac surgery and to an emphasis on early extubation. Most anesthesiologists use a balanced technique involving the administration of lower doses of narcotics with an inhalational agent. This approach allows the anesthesiologist to derive the benefits of each of these agents while minimizing side effects.
The IV agent propofol is an alternative mode of delivering general anesthesia. An alkyl phenol that can be used for both induction and maintenance of general anesthesia, propofol can cause profound hypotension because of reduced arterial tone with no change in HR. Its major advantage is rapid clearance with few residual effects on awakening, but because it is expensive, its current use tends to be limited to operations of brief duration. Despite its hemodynamic effects, propofol has been used extensively to assist in early extubation after CABG.
Current evidence indicates that there is no single “best” general anesthetic technique for patients with CAD who are undergoing noncardiac surgery, which has led to abandonment of the concept of a cardiac anesthetic.
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