Cardiovascular disease is the leading cause of death worldwide. Of the 200 million patients who undergo noncardiac surgery each year the world over, approximately 10 million have a major perioperative cardiac complication within 30 days.¹ Taken by itself, perioperative death constitutes the third leading cause of death in the United States and myocardial injury after noncardiac surgery is associated with a population attributable risk of 34% for death at 30 days in a recent international cohort analysis.^2,3 With an aging and increasingly comorbid population, these numbers are expected to grow.

Cardiovascular perioperative risk assessment has become a vital tool for evaluating patients prior to surgery to optimize their cardiovascular safety and initiate lifestyle modifications that coupled together provide short- and long-term benefits. Myocardial perfusion imaging (MPI) can play an important role in this process. The American College of Cardiology/American Heart Association (ACC/AHA) task force committee created guidelines for the perioperative risk assessment of cardiovascular disease for noncardiac surgery. Since the last iteration of the guidelines in 2007, data on perioperative cardiac risk factor modification and management have significantly changed, and the guidelines were subsequently updated in 2014.⁴

Goals of Preoperative Evaluation

As a physician evaluates a patient prior to noncardiac surgery, several goals should be kept in mind:

1. 
   

   Identify unstable patients who are at high risk for perioperative cardiac events.

   
   
2. 
   

   Identify the risk of the proposed surgery (Table 16-1).

   
   
3. 
   

   Assess risk for major adverse perioperative cardiovascular events using a validated risk prediction tool.

   
   
4. 
   

   Determine the patient’s functional capacity.

   
   
5. 
   

   Perform diagnostic testing and interventions to reduce perioperative morbidity and mortality or cancel the planned procedure.

   
   
6. 
   

   Intervene to reduce long-term cardiovascular morbidity and mortality.

   
   
7. 
   

   Follow-up with the patient postoperatively, when most perioperative cardiac events occur.

The preoperative evaluation begins with a thorough history with special emphasis on the need to identify clinical markers of perioperative risk as well as to assess functional capacity.

In 2002, the ACC/AHA guidelines delineated major, intermediate, and minor risk factors for perioperative cardiac events. In 2007, the guidelines sought to identify patients at high risk for complications with surgery due to serious cardiac conditions such as unstable coronary syndromes, severe angina, recent myocardial infarction (MI), decompensated heart failure (HF), significant arrhythmias, and severe valvular disease that require urgent evaluation regardless of impending surgery. The most recent update in 2014 reflects a paradigm shift in the methodology of guidelines preparation that continues to evolve.^4,5 In estimating risk, they dichotomize combined clinical and surgical risk into low (major adverse cardiac event [MACE] probability <1%) and elevated (MACE probability ≥1%).

The revised cardiac risk index (RCRI), devised and validated by Lee et al., remains the predominantly used and recommended tool for the estimation of MACE risk in the updated guidelines.⁶ The RCRI defined six independent risk correlates of cardiac risk for stable patients undergoing nonurgent major noncardiac surgery: high-risk surgery, history of ischemic heart disease, history of congestive HF, history of cerebrovascular disease, preoperative treatment with insulin, and preoperative serum creatinine >2.0 mg/dL. The rates of major cardiac complications with 0, 1, 2, or >3 in the validation cohort of 1422 patients were 0.4%, 0.9%, 7%, and 11%, respectively.⁶ The updated guidelines also highlight two newer tools developed by the American College of Surgeons National Surgical Quality and Improvement Program (NSQIP)—the MI and cardiac arrest risk prediction tool and the surgical risk calculator—but note that they have not been externally validated and use definitions of MI and assessments of physical status that are not standardized. Furthermore, the updated guidelines highlight a growing interest in the use of clinical biomarkers for multivariate risk prediction, but also note that information on how to treat based on such serologic tests still requires further investigation.^4,7,8

The assessment of functional capacity is critical for preoperative evaluation (Table 16-2). Poor functional capacity in patients with known CAD or prior MI is associated with an increased risk of subsequent cardiac events.⁹ Multiple investigators have studied the importance of functional capacity assessment for preoperative risk stratification.^10–12 These and other studies suggest that poor functional status identifies patients at high risk for perioperative complications. Therefore, it is extremely important to determine the patient’s maximal activity during daily activities and assess his or her functional capacity. This also could be assessed by treadmill exercise stress testing. Patients with poor functional capacity may require further evaluation, including MPI in multiple clinical situations as detailed later in this chapter.

Based on the above information a stepwise approach in the updated ACC/AHA guidelines can be used to determine if a patient needs perioperative cardiac assessment for coronary artery disease (Fig. 16-1).⁴

Emphasis should be placed on identifying evidence of disease states that might impact perioperative events, such as severe aortic stenosis, other severe valvular diseases, decompensated HF, unstable coronary syndromes, diabetes mellitus, and peripheral vascular disease. The aforementioned algorithm for assessing coronary artery disease preoperatively does not account for nonischemic cardiovascular events such as HF, valvular heart disease, pulmonary vascular disease and arrhythmias, which are beyond the scope of this chapter, but are otherwise addressed separately in the updated guidelines.^13,14 Briefly, nonetheless, the updated perioperative guidelines recommend addressing clinically significant moderate or severe valvular heart disease prior to elective noncardiac surgery, a continuation of targeted therapy for chronic pulmonary vascular disease and/or assessment by a pulmonary hypertension specialist as needed and a perioperative plan for management of a patient’s cardiac implantable electronic device should he or she have one to reduce perioperative cardiovascular morbidity and mortality.⁴

Although indicated less often in current practice, noninvasive cardiac testing can be a valuable component of the preoperative evaluation. The expertise of the local laboratory in identifying advanced coronary disease is probably more important than the particular type of test. However, there are certain contraindications to exercise, dobutamine, or vasodilator stress imaging tests that should be considered before selecting a test.

Myocardial Perfusion Imaging

Thus far, this chapter has dealt with perioperative risk assessment using primarily clinical data and exercise capacity. Despite the value of this information, it has been recognized that further data may be beneficial in selected patients. Landmark studies demonstrated that stress MPI could stratify patients into low- or high-risk groups. This risk stratification is helpful for both short-term (perioperative) and long-term prediction of cardiac events.

Short-Term Prognosis (Perioperative Period)

Clinical variables often define a low-risk group for whom no further testing may be needed and a high-risk group that may need further assessment with the intention for revascularization and/or intensive medical therapy. However, for some of the patients in the intermediate-risk group, further assessment with noninvasive testing would be needed. Radionuclide imaging is a well-established tool to risk stratify patients undergoing major noncardiac surgeries.

In studies by Eagle et al. both low- and high-risk patients were identified by clinical variables.^11,12 However, the intermediate-risk group had a 15.5% likelihood of developing perioperative cardiac complication. This group was further classified by dipyridamole thallium into patients with no ischemia who had a 3.2% perioperative event rate. In contrast, patients with ischemia had a 29.6% event rate (Fig. 16-2). This effectively reclassified the intermediate-risk group into either a low- or a high-risk group.

Further evidence to support selective use of preoperative dipyridamole thallium comes from L’Italien et al.¹⁵ In a multicenter study, they developed a prediction model in 567 patients on the basis of clinical variables (age >70 years, angina, history of MI, diabetes mellitus, history of congestive HF, and prior revascularization). A second model was developed from dipyridamole-thallium imaging. The models were then validated in a separate cohort of 514 patients. The observed and predicted cardiac event rates were similar for both patient sets. The addition of dipyridamole-thallium data reclassified more than 80% of the intermediate-risk patients into low-risk (3% event rate) and high-risk (19% event rate) categories. However, it provided no further stratification for patients previously classified as low- or high-risk by the clinical model. Thus, clinical markers reliably stratify risk in patients undergoing vascular surgery, and the selective use of myocardial imaging provides additional risk stratification in patients classified as intermediate risk.

The presence of ischemia on MPI identifies patients at higher risk, as noted earlier. The extent of ischemia can further classify this group of patients. Shaw et al. performed a meta-analysis of 15 studies that have available cardiac event rates after vascular surgery.¹⁶ Ten studies using dipyridamole thallium were identified (1994 patients). The perioperative event rates (death or MI) were 3% for patients with normal results, 7% for patients with fixed defects, and 9% for patients with reversible defects. Dipyridamole-induced ECG ST-segment depression occurred in 7% of patients and was associated with a cardiac event (death or MI) in 14% of patients. Furthermore, higher event rates were associated with larger perfusion defects. The event rate was 14% in patients with one or more reversible defects versus 30% in patients with two or more reversible defects. Therefore, patients with larger perfusion defects or evidence of multivessel ischemia have a worse prognosis.

The predictive value of thallium redistribution (ischemia) for death or MI ranged from 4% to 20% in reports that were selected in the ACC/AHA task force report on preoperative testing.¹⁷ The positive predictive value has decreased over time for MPI as this information is used to guide therapeutic interventions, such as intensive medical therapy or coronary revascularization. Moreover, the results of radionuclide imaging may lead to the performance of less extensive procedures or even cancellation of surgery. Nonetheless, the negative predictive value is very high (approximately 99%), and the prognosis associated with a normal scan is excellent.¹⁷

Fewer studies are available with technetium-99m agents, which are the contemporary standard. Stratmann et al. reported on the value of dipyridamole Tc-99m-sestamibi scintigraphy in 285 consecutive patients being considered for major and minor nonvascular surgery and in 229 consecutive patients being considered for vascular surgery.^18,19 Perioperative cardiac events included unstable angina, ischemic pulmonary edema, nonfatal MI, or cardiac death. Twelve events (4%) occurred in the whole cohort with 1 occurring in the 89 patients undergoing minor procedures and 11 occurring in the 140 patients undergoing major procedures.¹⁸ Perioperative cardiac events occurred in 4% of patients with a normal study, 24% with evidence of ischemia, and 37% with a fixed defect. In the second study by the same authors, the event rate was 3% in patients with a normal scan, 5% with an abnormal scan, and 6% with evidence of ischemia.¹⁹ Similar perioperative risk was reported in the group of patients who were identified to have ischemia and had intensive medical therapy or revascularization in comparison to those who had no ischemia. Thus, preoperative evaluation appears equally effective using Tc-99m sestamibi or thallium-201. In addition, although many of the studies utilized planar imaging, SPECT imaging has been documented to be effective in this role as well.²⁰