American College of Cardiology

EAGLE ET AL., PERIOPERATIVE CARDIOVASCULAR EVALUATION FOR NONCARDIAC SURGERY UPDATE
http://www.acc.org/clinical/guidelines/perio/update/periupdate_index.htm

ACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery

A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery)

III. Disease-Specific Approaches

A. Coronary Artery Disease

1. Patients With Known CAD
In some patients, the presence of coronary disease may be obvious, such as an acute MI, bypass grafting, coronary angioplasty, or a coronary angiogram showing luminal obstructions or irregularities. On the other hand, many patients without cardiac symptoms may have severe double- or triple-vessel disease that is not clinically obvious because the patients may present atypically or are functionally limited by severe arthritis or peripheral vascular disease. Such patients may benefit from noninvasive testing (Figure 1, Table 3) if the patient is a candidate for myocardial revascularization. In patients with known CAD, as well as those with previously occult coronary disease, the questions become ⁽¹⁾ What is the amount of myocardium in jeopardy? ⁽³⁹⁰⁾ What is the ischemic threshold, i.e., the amount of stress required to produce ischemia? and ⁽³⁾ What is the patient's ventricular function? Clarification of these questions is an important goal of the preoperative history, physical examination, and selected noninvasive testing used to determine the patient's prognostic gradient of ischemic response during stress testing (Table 5). On the other hand, many patients do not require noninvasive testing, particularly if they are not candidates for myocardial revascularization.

2. Patients With Major Risk Factors for CAD
Multiple risk factors have been identified that predispose the patient to the development of CAD and increase perioperative risk. Age, gender, and diabetes mellitus influence the outcome of patients undergoing noncardiac surgery. Some factors, such as diabetes mellitus, not only increase the likelihood and extent of coronary disease but also predispose the patient to complications, such as infection and hyperglycemia or hypoglycemia, which may add to the hemodynamic stress of the operation. Additionally, patients with diabetes mellitus may have a higher incidence of CAD and a higher incidence of silent myocardial ischemia and infarction than the general population ^(44-46).

Advanced age is a special risk, not only because of the increased likelihood of coronary disease, but because of the effects of aging on the myocardium. Heart muscle is terminally differentiated soon after birth, and the number of cardiac myocytes decreases with age ⁽⁴⁷⁾. The mortality of acute MI increases dramatically in the aged ⁽⁴⁸⁾. This phenomenon may be due in part to the decreased myocardial reserve from a smaller number of residual myocardial cells. Intraoperative or perioperative MI has a higher mortality in the aged ^(12,21,22).

Gender is important because premenopausal women have a lower incidence of CAD, and in general CAD occurs 10 or more years later in women than in men ⁽⁴⁹⁾. Women who have premature menopause, such that as after oophorectomy, are an exception to this rule. Diabetic women have an increased risk, that is equivalent to men of the same age. The mortality rate after acute MI is greater for women than for men, but older age and diabetes mellitus account for much of this difference ⁽⁵⁰⁾. Whether or not other factors such as coronary artery size or different pathophysiology also contribute to the increased risk in women is not yet fully understood.

Vascular disease presents a special problem because of its association with a higher incidence of CAD and because the limited activity imposed by claudication may mask coronary disease. A full discussion of the implications of peripheral vascular disease can be found in section IV.

B. Hypertension

Numerous studies ^{(12,15,18,21,51,52)} have shown that stage 1 or stage 2 hypertension (systolic blood pressure below 180 mm Hg and diastolic blood pressure below 110 mm Hg) are not independent risks for perioperative cardiovascular complications. However, hypertension is common, and treatment has been shown to be associated with decreased death rates from stroke and CHD in the nonsurgical setting. Unfortunately, all too few patients with hypertension are treated, and fewer yet have their hypertension controlled. Accordingly, the perioperative evaluation is a unique opportunity to identify patients with hypertension and initiate appropriate therapy. On the other hand, as a universally measured variable with a recognized association with CAD, hypertension serves as a useful marker for potential CAD ⁽⁵³⁾. In addition, several investigators have demonstrated exaggerated intraoperative blood pressure fluctuation with associated ECG evidence of myocardial ischemia in patients with preoperative blood pressure elevation ^(54-57). This effect can be modified by treatment ^(55-60). Because intraoperative ischemia correlates with postoperative cardiac morbidity ^(51,61), it follows that control of blood pressure preoperatively may help reduce the tendency to perioperative ischemia. Although an elevated blood pressure on an initial recording in a patient with previously undiagnosed or untreated hypertension has been shown to correlate with blood pressure lability under anesthesia ⁽⁶¹⁾, the definition of the severity of hypertension rests with subsequent recordings in a nonstressful environment ⁽⁵³⁾. In patients undergoing therapy for hypertension, a careful review of current medications and dosage, along with known intolerance to previously prescribed drugs, is essential. The physical examination should include a search for target-organ damage and evidence of associated cardiovascular pathology. A funduscopic examination may provide useful data regarding the severity and chronicity of hypertension.

The physical examination and simple laboratory tests can rule out some of the rare but important causes of hypertension. Further evaluation to exclude secondary hypertension is rarely warranted before necessary surgery, but in patients with severe hypertension, particularly of recent onset, it may be appropriate to delay elective surgery while the patient is evaluated for curable causes of hypertension. If pheochromocytoma is a serious possibility, surgery should be delayed to permit its exclusion. A long abdominal bruit may suggest renal artery stenosis. A radial to femoral artery pulse delay suggests coarctation of the aorta, whereas hypokalemia in the absence of diuretic therapy raises the possibility of hyperaldosteronism.

If the initial evaluation establishes hypertension as mild or moderate and there are no associated metabolic or cardiovascular abnormalities, there is no evidence that it is beneficial to delay surgery ⁽⁶²⁾. Several investigators have established the value of effective preoperative blood pressure control among patients with established hypertension ^{(56,57,60,63)}, and antihypertensive medications should be continued during the perioperative period. Particular care should be taken to avoid withdrawal of beta-blockers and clonidine because of potential heart rate or blood pressure rebound. In patients unable to take oral medications, parenteral beta-blockers and transdermal clonidine may be used. For patients with newly established mild hypertension, institution of therapy may be delayed until after surgery to avoid creation of instability in heart rate or blood pressure.

Stage 3 hypertension (systolic blood pressure greater than or equal to 180 mm Hg and diastolic blood pressure greater than or equal to 110 mm Hg) should be controlled before surgery. In many such instances, establishment of an effective regimen can be achieved over several days to weeks of preoperative outpatient treatment. If surgery is more urgent, rapid-acting agents can be administered that allow effective control in a matter of minutes or hours. Beta-blockers appear to be particularly attractive agents. Several reports have shown that introduction of preoperative beta-adrenergic blockers leads to effective modulation of severe blood pressure fluctuations and a reduction in the number and duration of perioperative coronary ischemic episodes ^(55-60). The preoperative administration of beta-adrenergic blocking drugs has been shown to decrease the incidence of postoperative atrial fibrillation ⁽²⁵⁰⁾, and in patients who have or are at risk for CAD who must undergo noncardiac surgery, treatment with beta blockers during hospitalization can reduce mortality and the incidence of cardiovascular complications ^(251,252).

Interestingly, patients with preoperative hypertension appear more likely to develop intraoperative hypotension than nonhypertensive persons; this is particularly true for patients taking ACE inhibitors ⁽²⁵³⁾. In some patients, this may be related to a decrease in vascular volume. In one report, hypotension during anesthesia was associated with a greater incidence of perioperative cardiac and renal complications than intraoperative hypertension, although other studies have not shown this ⁽⁵⁷⁾.

C. Heart Failure

Heart failure has been identified in several studies as being associated with a poorer outcome when noncardiac surgery is performed. In the study by Goldman et al ⁽¹²⁾, the presence of a third heart sound or signs of HF were associated with a substantially increased risk during noncardiac surgery. Detsky et al ⁽²²⁾ identified alveolar pulmonary edema as a significant risk factor, and in the report by Cooperman et al ⁽²⁴⁾, HF also bestowed a significant risk. Every effort must be made to detect unsuspected heart failure by a careful history and physical examination. If possible, it is important to identify the etiology of HF, because this may have implications concerning risk of death vs. perioperative HF. For instance, prior HF due to hypertensive heart disease may portend a different risk than prior HF resulting from CAD.

D. Cardiomyopathy

There is little information on the preoperative evaluation of patients with cardiomyopathy before noncardiac surgery. At this time, preoperative recommendations must be based on a thorough understanding of the pathophysiology of the myopathic process. Every reasonable effort should be made before surgery to determine the cause of the primary myocardial disease. For example, infiltrative diseases such as amyloidosis may produce either systolic or diastolic dysfunction. Knowledge of this fact may alter intraoperative and postoperative management of intravenous fluids. In patients with a history or signs of HF, preoperative assessment of left ventricular function may be recommended to quantify the severity of systolic and diastolic dysfunction. This information is valuable for both intraoperative and postoperative management. This assessment may include echocardiography.

Hypertrophic obstructive cardiomyopathy poses special problems. Reduction of blood volume, decreased systemic vascular resistance, and increased venous capacitance may cause a reduction in left ventricular volume and thereby potentially increase a tendency to outflow obstruction with potentially untoward results. Furthermore, reduced filling pressures may result in a significant fall in stroke volume because of the decreased compliance of the hypertrophied ventricle. Catecholamines should be avoided because they may increase the degree of dynamic obstruction and decrease diastolic filling. In a relatively small series of 35 patients with hypertrophic obstructive cardiomyopathy, there were no deaths or serious ventricular arrhythmias during or immediately after general surgical procedures; one patient had major vascular surgery. In the 22 patients who underwent catheterization, the mean rest and peak provokable gradients were 30 and 81 mm Hg, respectively. The only patient suffering a perioperative MI had two-vessel coronary disease. Significant arrhythmias or hypotension requiring vasoconstrictors occurred in 14% and 13% of patients, respectively ⁽⁶⁴⁾. In another study, 77 patients with hypertrophic obstructive cardiomyopathy who underwent noncardiac surgery were evaluated. There were no deaths, but these patients had a significant incidence of adverse cardiac events, frequently manifested as HF. Independent risk factors for adverse outcome in all patients included major surgery and increasing duration of surgery. Echocardiographic features, including resting outflow tract gradient, were not associated with adverse cardiac events ⁽²⁵⁴⁾.

E. Valvular Heart Disease

Cardiac murmurs are common in patients facing noncardiac surgery. The consultant must be able to distinguish organic from functional murmurs, significant from insignificant murmurs, and the origin of the murmur to determine which patients require prophylaxis for endocarditis and which patients require further quantitation of the severity of the valvular lesion.

Severe aortic stenosis poses the greatest risk for noncardiac surgery ⁽¹²⁾. If the aortic stenosis is severe and symptomatic, elective noncardiac surgery should generally be postponed or canceled. Such patients require aortic valve replacement before elective but necessary noncardiac surgery. On the other hand, in patients with severe aortic stenosis who refuse cardiac surgery or are otherwise not candidates for aortic valve replacement, noncardiac surgery can be performed with a mortality risk of approximately 10% ^(255,256). In rare instances, percutaneous balloon aortic valvuloplasty may be justified when the patient is not a candidate for valve replacement.

Mitral stenosis, although increasingly rare, is important to recognize. When stenosis is mild or moderate, the consultant must ensure control of heart rate during the perioperative period because the reduction in diastolic filling period that accompanies tachycardia can lead to severe pulmonary congestion. Significant mitral stenosis increases the risk of HF. However, preoperative surgical correction of mitral valve disease is not indicated before noncardiac surgery, unless the valvular condition should be corrected to prolong survival and prevent complications, unrelated to the proposed noncardiac surgery. When the stenosis is severe, the patient may benefit from balloon mitral valvuloplasty or open surgical repair before high-risk surgery ⁽⁶⁵⁾.

Aortic regurgitation needs to be identified, not only for appropriate prophylaxis for bacterial endocarditis but also to ensure appropriate medical treatment. Careful attention to volume control and afterload reduction is recommended. In contrast to mitral stenosis, severe aortic regurgitation is not benefited by unusually slow heart rates, which can increase the volume of regurgitation by increasing the duration of time in diastole. Tachycardia thus reduces the time of regurgitation in severe aortic regurgitation.

Mitral regurgitation has many causes, the most common being papillary muscle dysfunction and mitral valve prolapse. Perioperative antibiotic prophylaxis is recommended for patients with mitral valve prolapse who have clinical evidence of mitral valve regurgitation or echocardiographic evidence of thickening and/or redundancy of the valve leaflets ⁽¹³⁾. Because perioperative volume shifts may cause a patient with an isolated click to develop mitral regurgitation, auscultation in the sitting, standing, squatting, and standing-after-squatting positions may identify a tendency to volume- or stress-related regurgitation.

Patients with severe mitral regurgitation (often manifested clinically by an apical holosystolic murmur, a third heart sound, and a diastolic flow rumble) may benefit from afterload reduction and administration of diuretics to produce maximal hemodynamic stabilization before high-risk surgery. Occasionally this therapy can best be accomplished by treatment in an intensive care unit with a catheter to monitor pulmonary artery pressure. It is also important for the consultant to note even mild reduction of the left ventricular ejection fraction (LVEF) in patients with mitral regurgitation. Because the low-pressure left atrium acts as a low-impedance sink in patients with severe mitral regurgitation, LVEF may overestimate true left ventricular performance. In such patients, even a mildly reduced LVEF may be a sign of reduced ventricular reserve.

Patients with a mechanical prosthetic valve are of concern because of the need for endocarditis prophylaxis ⁽¹³⁾ when they undergo surgery that may result in bacteremia and the need for careful anticoagulation management. The Fifth Consensus Conference on Anticoagulation recommends the following ⁽²⁵⁷⁾:

For patients who require minimally invasive procedures (dental work, superficial biopsies), the recommendation is to briefly reduce the international normalized ratio (INR) to the low or subtherapeutic range and resume the normal dose of oral anticoagulation immediately after the procedure. Perioperative heparin therapy is recommended for patients in whom the risk of bleeding with oral anticoagulation is high and the risk of thromboembolism without anticoagulation is also high [mechanical valve in the mitral position, Bjork-Shiley valve, recent (i.e., less than one year) thrombosis or embolus, or three or more of the following risk factors: atrial fibrillation, previous embolus at any time, hypercoagulable condition, mechanical prosthesis and LVEF less than 30% ⁽²⁵⁸⁾]. For patients between these two extremes, physicians must assess the risk and benefit of reduced anticoagulation vs. perioperative heparin therapy.

F. Arrhythmias and Conduction Defects

Cardiac arrhythmias and conduction disturbances are not uncommon findings in the perioperative period ^(12,16,67), particularly in the elderly. In some studies, both supraventricular and ventricular arrhythmias have been identified as independent risk factors for coronary events in the perioperative period ^(12,67). More recent detailed studies using continuous ECG monitoring found that asymptomatic ventricular arrhythmias, including couplets and nonsustained ventricular tachycardia, were not associated with an increase in cardiac complications after noncardiac surgery ⁽²⁴¹⁾. Nevertheless, the presence of an arrhythmia in the preoperative setting should provoke a search for underlying cardiopulmonary disease, ongoing myocardial ischemia or infarction, drug toxicity, or metabolic derangements.

Some cardiac arrhythmias, although relatively benign, may unmask underlying cardiac problems; for example, supraventricular arrhythmia can produce ischemia by increasing myocardial oxygen demand in patients with coronary disease. Rarely, arrhythmias, because of the hemodynamic or metabolic derangements they cause, may deteriorate into more life-threatening rhythm disturbances; for example, atrial fibrillation with a rapid ventricular response in a patient with an accessory bypass pathway may degenerate into ventricular fibrillation. Ventricular arrhythmias, whether single premature ventricular contractions, complex ventricular ectopy, or nonsustained ventricular tachycardia, usually do not require therapy except in the presence of ongoing or threatened myocardial ischemia. Although frequent ventricular premature beats and nonsustained ventricular tachycardia are considered risk factors for the development of intraoperative and postoperative arrhythmias and sustained ventricular arrhythmias during long-term follow-up, they are not associated with an increased risk of nonfatal MI or cardiac death in the perioperative period ^(240,241). Therefore, aggressive monitoring or treatment in the perioperative period may not be necessary. However, physicians should have a low threshold to institute prophylactic beta-blocker therapy in patients at increased risk of developing a perioperative or postoperative arrhythmia. Several recent studies suggest that beta-blocker therapy can reduce mortality and the incidence of cardiovascular complications (including the development of arrhythmias) during and for up to two years after surgery ^{(250-252,259)}.

High-grade cardiac conduction abnormalities, such as complete atrioventricular block, if unanticipated, can increase operative risk and may necessitate temporary or permanent transvenous pacing. On the other hand, patients with intraventricular conduction delays, even in the presence of a left or right bundle-branch block, and no history of advanced heart block or symptoms rarely progress to complete heart block perioperatively ⁽⁷¹⁾. The availability of transthoracic pacing units makes the decision for temporary transvenous pacing less critical.

G. Implanted Pacemakers and ICDs

Each year more than 200,000 patients undergo placement of a permanent pacemaker, and more than 60,000 patients undergo placement of an implantable defibrillator. The presence of a pacemaker or ICD has important implications regarding preoperative, intraoperative, and postoperative patient management. The situations in which device malfunction may occur, as well as the techniques that may be used to prevent them, are discussed in Section VII.

H. Pulmonary Vascular Disease

There are no reported studies that specifically assess the perioperative risk associated with pulmonary vascular disease in patients having noncardiac surgery. In fact, there are no systematic studies of the risk of noncardiac surgery for patients with congenital heart disease, corrected or uncorrected ⁽⁷²⁾. A number of reports have evaluated cardiovascular function many years after surgery for congenital heart disease. Five years after surgery for ventricular septal defect or patent ductus arteriosus, pulmonary vasoreactivity often remains abnormal, increasing to high levels during hypoxia. Such patients may not tolerate intraoperative or postoperative hypoxia as well as normal individuals.

Patients with congenital heart disease have also demonstrated a reduced cardiac reserve during exercise ⁽⁷³⁾. Postoperative studies of patients with coarctation of the aorta or tetralogy of Fallot have demonstrated findings consistent with underlying ventricular dysfunction ^(74,75). These observations should be kept in mind when such patients are evalutated before noncardiac surgery. Patients receiving primary cardiac repair at a younger age in the present era may be less prone to postoperative ventricular dysfunction because of improved surgical techniques.

Although most experts agree that pulmonary hypertension poses an increased risk for noncardiac surgery, no organized study of the problem has been performed. The only analogous situation is labor and delivery for women with Eisenmenger syndrome due to a congenital intracardiac shunt. Peripartum mortality was reported to be between 30% and 70% in 1971, but no recent data exist to clarify whether or not this has fallen with improvements in care ⁽⁷⁶⁾. In patients with severe pulmonary hypertension and a cardiac shunt, systemic hypotension results in increased right-to-left shunting and predisposes the patient to development of acidosis, which can lead to further decreases in systemic vascular resistance. This cycle must be recognized and appropriately treated.