The assessment of the surgical patient undergoing vascular surgery is a complex process that requires integration of multiple areas of expertise. The classic concept of clearing a patient for surgery has been replaced with an integrated approach of interdisciplinary cooperation that focuses on assessment of existing disorders, optimization of resilience and reserve in anticipation of increased preoperative demand, avoidance of therapeutic conflicts, and identification of potential procedure-specific risks. Silverman and Rosenbaum identify 4 separate phases of the preoperative assessment: documentation of existing conditions, optimization of the conditions identified, risk assessment, and planning.8
Risk assessment combines information obtained by documentation and changes due to optimization with the anticipated physiologic disturbance of the planned surgery (and accompanying anesthetic),8 and will have value only if it leads to risk modification or otherwise influences the decisions regarding surgical or anesthetic procedures.
Although occasionally the atherosclerotic process manifests itself in a discrete vascular segment, the more common presentation is diffuse involvement of several organ systems. The vascular patient population has a high incidence of significant CAD, for example, left ventricular systolic dysfunction (left ventricular ejection fraction less than 40%) is 5 times more common in patients with cerebrovascular disease or peripheral arterial disease compared with matched controls.9
In addition, vascular patients often report a heavy smoking history, and some degree of pulmonary compromise is expected. Diabetes mellitus is frequently associated with vascular disease, necessitating appropriate evaluation and treatment in the preoperative period. Hypertension is both a predisposing factor for vascular disease and a consequence of its development.
These risk-assessment models are based on findings from the history, physical, and additional information from diagnostic studies. As cardiac complications pose one of the most significant risks to patients undergoing major vascular surgery, the continuing debate concerns the appropriate management sequence to be followed once the risk is predicted. That is, should other tests, such as dipyridamole-thallium imaging (DTI) or dobutamine stress echocardiography (DSE) be performed toward selection of a subset of patients to be revascularized with percutaneous transluminal angioplasty or coronary artery bypass graft (CABG) prior to vascular surgery, or rather, should the patient proceed directly to vascular surgery with aggressive perioperative medical management in an attempt to reduce risk.
Clinical Predictors of Perioperative Risk
Patients undergoing major vascular surgery constitute a particular challenge, because these are high-risk operations in a patient population with a high prevalence of significant CAD. Hertzer et al showed that only 8% of 1000 vascular surgery patients in whom coronary angiography was performed had normal coronary arteries, 30% had severe coronary artery disease, and more than 90% had significant (>70% stenosis) disease in at least 1 major coronary artery.10
Peripheral vascular surgery is associated with greater cardiac morbidity and overall mortality than other forms of noncardiac surgery. Physiologic factors associated with surgery predispose to myocardial ischemia, which is more pronounced in patients with underlying coronary disease. Myocardial ischemia can result from increases in myocardial oxygen demand secondary to increases in blood pressure and heart rate, elevated preload, and increased contractility, or from decreases in oxygen supply due to hypotension, tachycardia, increased filling pressure, anemia, hypoxemia, and obstructed coronary blood flow due to acute thrombosis or spasm. It is important to keep in mind that the leading causes for acute coronary and cerebrovascular syndromes (unstable angina, MI, sudden death, and stroke) are plaque disruption and thrombus formation in mildly stenotic lesions that may not be detectable by angiography or cardiovascular testing.2
Perioperative myocardial infarction (MI) is reported to occur in 4% to 15% of patients undergoing peripheral vascular surgery and accounts for more than 50% of perioperative mortality.11,12 Cardiac risk also remains high in the subsequent months for patients who have suffered a perioperative cardiac event. Mangano et al have found that patients surviving a postoperative in-hospital MI had a 28-fold increase in the rate of cardiac complications within 6 months following surgery.13 L'Italien et al investigated 547 patients undergoing vascular surgery from 2 medical centers who underwent aortic, infrainguinal, or carotid vascular surgery. Perioperative MI occurred in 6% of patients undergoing aortic and carotid artery surgery and in 13% of patients undergoing infrainguinal procedures. Although patients undergoing infrainguinal procedures exhibited more than twice the risk for perioperative MI compared with patients undergoing aortic surgery, this value was reduced to insignificant levels after adjustment for comorbid factors.14 Using the Medicare National Inpatient Sample from 1994 through 1999, Birkmeyer et al noted that in high-volume hospitals, the perioperative mortality rates for carotid endarterectomy, lower-extremity bypass, and aneurysm surgery were 1.5%, 4.1%, and 3.9%, respectively.15
As stated in the guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery published by the American College of Cardiology (ACC) and the American Heart Association (AHA), "patients who require vascular surgery appear to have an increased risk for cardiac complications because (1) many of the risk factors that contribute to peripheral vascular disease (eg, diabetes mellitus, tobacco use, and hyperlipidemia) are also risk factors for CAD; (2) the usual symptomatic presentation for CAD in these patients may be obscured by exercise limitations imposed by advanced age, intermittent claudication, or both; and (3) major open vascular surgery may be associated with substantial fluctuations in intravascular/extravascular fluid volumes, cardiac filling pressures, systemic blood pressure, heart rate, and thrombogenicity."16
Multivariate analysis, initially developed by Goldman and based on routine clinical information and laboratory tests, identified combinations of factors that could estimate the risk of cardiac complications. More recently, Lee et al derived and validated a Revised Cardiac Risk Index (RCRI) for the prediction of cardiac risk in stable patients undergoing nonurgent major cardiac surgery. It is currently the most used model of risk assessment in noncardiac surgery. The authors identified 6 independent predictors of complications: high-risk type of surgery (intrathoracic, intra-abdominal, suprapubic vascular), history of CAD, history of congestive heart failure, history of cerebrovascular disease, preoperative treatment with insulin, preoperative serum creatinine greater than 2 mg/dL. These predictors were validated later in a cohort of 1422 patients. The predictive value was significant in all types of elective major noncardiac surgery except for abdominal aortic aneurysm surgery. Cardiac event rates for 0, 1, 2, and 3 or more than 3 of the 6 factors were 0.4%, 0.9%, 7%, and 11%, respectively.17
The current standards for preoperative cardiac evaluation of these patients are the guidelines published by the ACC and the AHA initially in 1996 and revised in 2002 and in 2007.16 The 2007 ACC/AHA guidelines identify a group of active cardiac conditions that when present indicate major clinical risk (Box 55-1) and for which patients should undergo evaluation and treatment before noncardiac surgery. Based on the widespread use of RCRI, the ACC/AHA 2007 perioperative guidelines have replaced the intermediate-risk category from the 2002 version of the guidelines with the following clinical risk factors: history of ischemic heart disease, history of compensated or prior heart failure, history of cerebrovascular disease, diabetes mellitus, and renal insufficiency. Also, the 2007 guidelines do not segregate clinical risk factors into major, intermediate, and minor. The guidelines provide a 5-step algorithm for determining which patients should undergo further cardiac testing based on functional capacity (Box 55-2), the surgery-specific risk (Box 55-3), and the presence of clinical risk factors (Fig. 55-3). Several studies have assessed the utility of the ACC/AHA guidelines for risk stratification. Licker et al compared data from 2 consecutive 4-year periods (1993-1996 control period vs 1997-2000 intervention period). The introduction of ACC/AHA protocols was associated with increased preoperative myocardial scanning (44.3% vs 20.6%) and coronary revascularization (7.7% vs 0.8%) as well as a significant decrease in the incidence of cardiac complications (11.3%-4.5%) and an increase in event-free survival at 1 year after surgery (91.3%-98.2%).18,19
Box 55-1 ||Download (.pdf)
Active Cardiac Conditions for Which the Patient Should Undergo Evaluation and Treatment Before Noncardiac Surgery
|Unstable coronary syndromes|
Unstable or severe angina (CCS class III or IV)a
|Decompensated HF (NYHA functional class IV; worsening or new-onset HF)|
High-grade atrioventricular block
Mobitz II atrioventricular block
Third-degree atrioventricular heart block
Symptomatic ventricular arrhythmias
Supraventricular arrhythmias (including atrial fibrillation) with uncontrolled ventricular rate (HR greater than 100 bpm at rest)
Newly recognized ventricular tachycardia
|Severe valvular disease|
Severe aortic stenosis (mean pressure gradient greater than 40 mm Hg, aortic valve area less than 1.0 cm2, or symptomatic)
Symptomatic mitral stenosis (progressive dyspnea on exertion, exertional presyncope, or HF)
Box 55-2 ||Download (.pdf)
Estimated Energy Requirements for Various Activities
|Can you…||Can you…|
Take care of yourself?
Eat, dress, or use the toilet?
Walk indoors around the house?
Walk a block or 2 on level ground at 2 to 3 mi/h (3.2 to 4.8 km/h)?
Climb a flight of stairs or walk up a hill?
Walk on level ground at 4 mi/h (6.4 km/h)?
Run a short distance?
Do heavy work around the house like scrubbing floors or lifting or moving heavy furniture?
|4 METs||Do light work around the house like dusting or washing dishes?||Participate in moderate recreational activities like golf, bowling, dancing, doubles tennis, or throwing a baseball or football?|
|Greater than 10 METs||Participate in strenuous sports like swimming, singles tennis, football, basketball, or skiing?|
Box 55-3 ||Download (.pdf)
|Cardiac Riska Stratification for Noncardiac Surgical Procedures|
|Risk Stratification||Procedure Examples|
|Vascular (reported cardiac risk often more than 5%)|
Aortic and other major vascular surgery
Peripheral vascular surgery
|Intermediate (reported cardiac risk generally 1% to 5%)|
Intraperitoneal and intrathoracic surgery
Head and neck surgery
|Lowb (reported cardiac risk generally less than 1%)|
Cardiac evaluation and care algorithm for noncardiac surgery based on active clinical conditions, known cardiovascular disease, or cardiac risk factors for patients 50 years of age or older.
*See Box 55-1 for active clinical conditions.
†See Box 55-2 for estimated MET level equivalent.
‡Clinical risk factors include ischemic heart disease, compensated or prior heart failure, diabetes mellitus, renal insufficiency, and cerebrovascular disease.
§Consider perioperative beta blockade for populations in which this has been shown to reduce cardiac morbidity/mortality.
ACC/AHA, American College of Cardiology/American Heart Association;HR, heart rate; LOE, level of evidence; and MET, metabolic equivalent.
[From Fleisher LA, Beckman JA, Brown KA, et al. ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 2002 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery) developed in collaboration with the American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, and Society for Vascular Surgery. J Am Coll Cardiol. 2007;50:1707-1732.]
Recent Myocardial Infarction and Angina
Acute MI is defined as a documented MI 7 days or less before the examination, and a recent MI is defined as a documented MI more than 7 days but less than or equal to 1 month before the examination.16 Recent myocardial infarction and unstable and severe angina represent active cardiac conditions for which patients should undergo evaluation and treatment before noncardiac surgery.16
Traditionally, risk assessment for noncardiac surgery was based on the time interval between the MI and the surgery. Older studies found as much as a 36% risk of reinfarction or cardiac death when patients underwent surgery within 3 months of a previous MI. The risk fell to 15% to 25% at 3 to 6 months, and 5% when surgery was performed after more than 6 months.20 However, due to preoperative optimization and intensive perioperative monitoring, the risk was lower in later studies.21
The ACC/AHA guidelines for perioperative evaluation of the cardiac patient undergoing noncardiac surgery advocate a wait period of 4 to 6 weeks after MI and before proceeding with an elective surgery; after that period, risk stratification is based on the presentation of the disease.
Risk stratification of patients with acute coronary syndromes such as unstable or severe angina begins upon presentation and continues throughout to predict those who are at high risk for further ischemic events or adverse outcomes. Such patients should not undergo noncardiac surgery except in the most emergent of circumstances.
Severe valvular disease is considered by the 2007 ACC/AHA guidelines as an active cardiac condition that when present may indicate major clinical risk. However, when the clinician is aware of the pathophysiologic implications of the disease and uses individual clinical judgment, patients can undergo surgery with a risk that is not so high, and may not be different from controls.
Severe aortic stenosis deserves special attention as it represents a risk factor for preoperative cardiac complications.22,23 The 2007 ACC/AHA guidelines recommend that in patients with symptomatic severe aortic stenosis elective noncardiac surgery "should generally be postponed or canceled" and such patients should undergo aortic valve replacement. If the aortic stenosis is severe but asymptomatic, elective surgery should be postponed if the valve has not been evaluated within the year.16
Diabetes has been strongly suggested as a predictor for perioperative cardiac morbidity after vascular surgery, and insulin therapy for diabetes mellitus has been identified as a significant risk factor for cardiac morbidity in the RCRI.17 Altered autonomic function in diabetes may predispose to greater intraoperative risk of blood pressure lability, variation of heart rate, gastroparesis, and decreased esophageal sphincter tone. Diabetic autonomic neuropathies can obscure symptoms of myocardial ischemia, thus adding to the already high incidence of "silent" ischemia seen in the perioperative period. The presence of diabetes in vascular surgery patients may identify a population in whom DTI is useful.
Preoperative evaluation of patients with pulmonary disease allows for optimization, risk stratification, and designing of strategies for reduction of postoperative pulmonary complications. The most important components of preoperative assessment of patients with known pulmonary disease are a thorough history and a comprehensive physical examination.24 Pulmonary function tests (PFT) may be useful to assess severity of disease and adequacy of bronchodilator therapy in patients in whom it is difficult to elicit this from history or physical examination.24 Arterial blood gases may be used to evaluate the degree of pulmonary disease and provide a baseline for subsequent clinical decisions.
Many vascular patients are chronic smokers; cigarette smoking increases the risk for postoperative pulmonary and nonpulmonary complications even in the absence of chronic lung disease.24 The risk of pneumonia is twice as high in smokers as in nonsmokers, and the development of hypoxemia in the postoperative period occurs more frequently and more severely in smokers as compared with nonsmokers.
The presence of preexisting renal disease (preoperative serum creatinine levels ≥2 mg/dL) increases the rates of morbidity and mortality for patients undergoing major vascular surgery16,25; therefore, a comprehensive preoperative evaluation of a vascular surgical patient should include an assessment of renal function.
Causes of baseline renal insufficiency include atherosclerosis of the renal arteries, hypertension, diabetic nephropathy, and depressed myocardial function. Contrast-enhanced imaging studies performed before surgeries also alter renal function by both a direct toxic effect and by a hyperosmolar-induced diuresis that reduces the intravascular volume. Intravascular volume expansion before, during, and after the angiographic study minimizes renal effects.
In the vascular patient undergoing abdominal aortic surgery there are several causes of renal impairment superimposing on an already precarious renal function. These additional causes of renal impairment include wide fluctuations in the intravascular volume and cardiac output; altered neuroendocrine milieu with increased epinephrine, norepinephrine, and renin secretion; and emboli shower dislodged by the aortic clamp and dysfunctional effects on renal hemodynamics from aortic cross-clamping.
Evolving technology and progress in surgical and anesthetic management has decreased the incidence of renal failure.
Preoperative electrocardiogram (ECG) abnormalities are observed in 40% to 70% of patients with CAD undergoing noncardiac surgery such as ST-segment and T-wave abnormalities (65%-90%) and Q waves (0.5%-8%). Abnormal ECG can be due to several other causes such as metabolic and electrolyte disturbances, pulmonary disease, conduction disturbances, and medications. Although some studies have demonstrated that the presence of ECG abnormalities such as Q waves, significant ST-segment elevation or depression, and left ventricular hypertrophy pattern have been associated with an increased incidence of cardiac complications in patients undergoing major noncardiac surgery,17 other studies have failed to demonstrate the predictive value of the preoperative 12-lead ECG.26
Noninvasive diagnostic tests have been proposed to evaluate the extent of CAD before noncardiac surgery and permit further stratification in patients deemed to be at intermediate risk after clinical evaluation. Detailed cardiac assessment and treatment are not feasible in the emergent setting. However, according to the 2007 ACC/AHA guidelines for preoperative evaluation of patients undergoing elective vascular surgery, noninvasive stress testing is reasonable in patients with 3 or more clinical risk factors (class IIa) or at least 1 to 2 clinical risk factors (class IIb) and poor functional capacity (<4 metabolic equivalents [METs]) who require vascular surgery if it will change management.16 One caveat of interpreting stress testing in the overall preoperative evaluation of the patient is that for the purpose of predicting perioperative cardiac events, stress testing has a high negative predictive value (90%-100%) but low positive predictive value (6%-67%), thus being more useful in reducing estimated risk if negative (or normal) than for identifying patients at very high risk if positive.27
Exercise ECG without myocardial imaging has been the traditional method for evaluating CAD, and is the standard method for determining functional capacity and detecting myocardial ischemia with a sensitivity of 68% to 81% and a specificity of 66% to 77%. Exercise tolerance appears to be more important than the ECG response to exercise. McPhail et al showed that the ability to perform moderate exercise or to achieve greater than 85% of predicted maximal heart rate during treadmill exercise testing is associated with a low risk of a postoperative cardiac event even in the presence of ST-segment depression more than 1 mm.28
Two groups of patients are excluded from performing exercise ECG testing: patients who cannot exercise (due to leg claudication, arthritis, deconditioning, or associated pulmonary disease) and patients who have abnormalities on the resting ECG such as preexcitation (Wolff-Parkinson-White) syndrome, a paced ventricular rhythm, more than 1 mm of ST-segment depression at rest, complete left bundle branch block, or ECG criteria for left ventricular hypertrophy. These patients may undergo pharmacological stress testing. The 2 most commonly used tests are dipyridamole-thallium myocardial perfusion imaging (DTI) and dobutamine stress echocardiography (DSE).
Radionuclide Myocardial Perfusion Imaging Methods
Radionuclide myocardial perfusion imaging (MPI) involves the visualization of a radiopharmaceutical that is distributed throughout the myocardium in proportion to coronary blood flow, thereby permitting the determination of relative blood flow in various regions of the heart. The vasodilators used for pharmacologic myocardial perfusion imaging are adenosine, regadenoson, and dipyridamole. Adenosine and dipyridamole are equally effective, but adenosine has the advantages of a very short half-life, rapid reversal of side effects after the test is completed, and possibly more predictable vasodilation. The vasodilator agents should be avoided in patients with resting hypotension (because these drugs lower the blood pressure), sick sinus syndrome, or a high degree atrioventricular (AV) block in the absence of backup pacing. In addition, adenosine and dipyridamole should not be used in patients with bronchospastic airway disease. The most frequently used myocardial perfusion agents are thallium-201 and technetium 99–labeled agents. Thallium-201 is taken up by cells similarly to potassium and is readily assimilated by healthy myocardial cells, and thus infarcted, ischemic, or hypoperfused areas appear as defects. After injection of thallium or 99-technetium, normal myocardium will show up on initial imaging while areas of infarction or hypoperfusion distal to a stenosis will appear as a defect. After dissipation of the dilatory effect and after a second injection of technetium, defects caused by ischemia will resolve while those caused by scarred infarcted tissue will persist.
MPI has a high sensitivity for detecting patients at risk for perioperative cardiac events. The negative predictive value for MI or cardiac death of a normal scan is very high at approximately 99%, and the positive predictive value of an abnormal scan with reversible defects is very low, varying between 2% and 20%.16 Given the low positive predictive value, this test is best used on patients at high clinical risk for perioperative cardiac events. The ability to identify patients at risk may be improved when taking into account the extent of ischemia rather than only its presence. A recent meta-analysis showed that the probability of MI or cardiac death ranged from 3% to 4% in patients with no or only fixed defects, to 9% in patients with reversible defects involving less than 20% of the left ventricle, to 18% and 45% in patients with reversible defects involving 30% to 49% and more than 50% of the left ventricle, respectively.29 In a meta-analysis of dypiridamole MPI for risk stratification before elective vascular surgery, Shaw et al showed that the pretest coronary disease probability was correlated with the positive predictive value of a reversible DTI, increasing 6-fold from low- to high-risk patient subsets. Cardiac event rates were low in patients without a history of coronary artery disease (1% in 176 patients) compared with patients with coronary disease and a normal or fixed-defect pattern (4.8% in 83 patients) and 1 or more thallium-201 redistribution abnormality (18.6% in 97 patients).30
Conversely, Baron et al studied a large consecutive population of patients undergoing abdominal aortic surgery and were unable to demonstrate an association between thallium redistribution and perioperative cardiac morbidity. In this study the presence of definite CAD and age greater than 65 years were better predictors of cardiac complications than perfusion imaging, raising the need for caution regarding the indiscriminate evaluation with DTI of patients undergoing vascular surgery.98
Dobutamine Stress Echocardiography
Dobutamine stress echocardiography (DSE) is preferred in patients with bronchospastic lung disease and in those with severe carotid stenosis because adenosine and dipyridamole may induce bronchospasm and hypotension. It also provides information about left ventricular function or valvular heart disease. As opposed to DTI, which is limited in its methodology by not increasing myocardial oxygen consumption, the administration of dobutamine mimics intraoperative conditions by increasing the heart rate. Similarly to other noninvasive testing, DSE had a high negative predictive value ranging from 93% to 100% and a relatively low positive predictive value up to 33%.16 Kertai et al performed a meta-analysis of studies looking at perioperative cardiac risk stratification in patients undergoing major vascular surgery (8119 patients). They concluded that DSE showed a positive trend toward better diagnostic performance than the other tests, but this was only significant in the comparison with MPI.31 The predictive value appears to vary with patient risk. This was illustrated in a recent analysis of 1097 patients who were assigned 1 point for each of the following clinical risk factors: age older than 70 years, current or prior angina and prior MI, congestive heart failure, or cerebrovascular event. The study showed that the additional predictive value of DSE is limited in clinically low-risk patients (<3 clinical risk factors) receiving β-blockers such that DSE may be avoided in a large number of patients who can proceed safely for surgery without delay. In patients with 3 or more risk factors, DSE provided additional prognostic information; patients without stress-induced ischemia had a much lower risk of events than those with stress-induced ischemia (among those receiving β-blockers, 2.0% vs 10.6%). Moreover, patients with limited stress-induced ischemia (1-4 segments) experienced fewer cardiac events than those with more extensive ischemia (≥5 segments).32 Other studies have suggested that the extent of the wall-motion abnormality and/or wall-motion change at low ischemic thresholds, particularly at a heart rate of less than 60% of age-predicted maximum, are important predictors of long-term or short-term outcomes.16
Transthoracic echocardiography (TTE) may add predictive information about the risk of postoperative cardiac complications in selected patients.33
A recent study evaluated the prevalence of left ventricular (LV) dysfunction in 1005 consecutive patients undergoing vascular surgery. Left ventricular dysfunction was diagnosed in 506 (50%) patients. Of the patients with LV dysfunction, 403 (80%) patients had asymptomatic LV dysfunction and 103 (20%) had symptomatic heart failure. Of the patients with asymptomatic LV dysfunction, 209 (52%) had asymptomatic isolated diastolic LV dysfunction and 194 (48%) had asymptomatic systolic LV dysfunction. This study also looked at the association of asymptomatic heart failure with perioperative cardiac events in patients undergoing vascular surgery and found that in open vascular surgery both asymptomatic systolic and isolated left ventricle diastolic dysfunctions were associated with 30-day cardiovascular events and long-term cardiovascular mortality. In endovascular surgery, only symptomatic heart failure was associated with 30-day cardiovascular events and long-term cardiovascular mortality.34
The 2007 ACC/AHA guidelines for preoperative evaluation of patients undergoing elective vascular surgery recommend preoperative evaluation of LV function in patients with dyspnea of unknown origin or in patients with current or prior heart failure with worsening dyspnea or change in clinical status (class IIa recommendation). However, based on recent findings some investigators suggest a move toward more routine cardiac echocardiography evaluation, especially in patients undergoing open vascular surgery.34
In the perioperative setting, many infarctions are the result of acute thrombosis of a noncritical stenosis, therefore limiting the value of routine angiography prior to major noncardiac surgery. The 2007 ACC/AHA guidelines for preoperative evaluation of patients undergoing elective vascular surgery state that indications for preoperative coronary angiography are similar to those identified for the nonoperative setting.16