Preoperative cardiac evaluation

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What is the natural history of perioperative cardiac morbidity?

• Perioperative cardiac morbidity occurs most commonly during the first 3 postoperative days and includes perioperative myocardial infarction (PMI), unstable angina, congestive heart failure, cardiac death, and nonfatal cardiac arrests. Studies suggest a peak incidence of PMI within the first 48 hours or earlier. Among patients with known ischemic heart disease, incidence of PMI is approximately 5%, with incidence decreasing to 2% to 4% among patients with risk factors but no history of ischemic heart disease, and decreasing still among patients with no risk factors. Additionally, mortality from PMI has decreased from previous rates of 30% to 50% to approximately 12%. A more recently described but separate syndrome from PMI is myocardial injury after noncardiac surgery (MINS). MINS is defined by elevated troponin in the perioperative period due to cardiac ischemia that does not meet criteria for MI set by the Fourth Universal Definition of Myocardial Infarction. While seemingly more benign, MINS is independently associated with the risk of death and cardiovascular complications in the year following surgery.

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What is the cause of perioperative cardiac morbidity?

• The perioperative stress response includes release of catecholamines and cortisol, leading to tachycardia and hypertension, which results in increased myocardial oxygen demand and ischemia. Ischemia is further exacerbated by extremes of blood pressure, anemia, hypoxemia, hypercarbia, and coronary vasoconstriction. Additionally, tissue injury and the hypercoagulable perioperative state may also lead to acute thrombosis. These factors combined lead to the two distinct mechanisms of PMI: (1) plaque rupture and acute thrombosis leading to acute coronary syndrome and (2) prolonged oxygen supply-demand mismatch leading to ischemia (type 1 versus type 2 using the universal definition). While demand ischemia predominates as the major cause of PMI and MINS, etiology must be determined due to differing therapeutic targets.

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What are the strongest predictors of perioperative cardiac events?

• For some specific patients, surgery represents a very high risk of cardiac complications and either therapy should be initiated preoperatively or the benefits of surgery must significantly outweigh the risks if the decision is to proceed to surgery. According to the 2014 American College of Cardiology/American Heart Association (ACC/AHA) Guidelines on Perioperative Cardiovascular Evaluation, active cardiac conditions for which the patient should undergo evaluation and treatment before noncardiac surgery include unstable coronary syndromes, and a recent MI. Based upon analyses of administrative data, the definition of a recent MI continues for at least the first 60 days for the purposes of preoperative evaluation. Additional important risk factors include active heart failure, severe valvular disease, and severe arrhythmias. A summary of active cardiac conditions for which the patient should undergo evaluation and treatment before elective noncardiac surgery is given in Table 69.1 .

  Table 69.1

  Active Cardiac Conditions for Which the Patient Should Undergo Evaluation and Treatment Before Noncardiac Surgery (Class I, Level of Evidence B)

  CONDITION	EXAMPLES
  Unstable coronary syndromes	Unstable or severe angina a (CCS class III or IV) b Recent MI c 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 uncontrolled ventricular rate (HR >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; HR , heart rate; MI , myocardial infarction; NYHA , New York Heart Association.

  a According to Campeau, L. (1976). Grading of angina pectoris [letter]. Circulation, 54 , 522–523.

  b May include stable angina in patients who are unusually sedentary.

  c The American College of Cardiology National Database Library defines recent MI as more than 7 days but less than or equal to 1 month (within 30 days).

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What is the American College of Surgeons National Surgical Quality Improvement Project risk calculator, and how should it be used clinically?

• The American College of Surgeons National Surgical Quality Improvement Project (ACS-NSQIP) risk calculator was developed based on 1,414,006 patients encompassing 1557 unique CPT codes. Risk factors are shown in Table 69.2 and include clinical factors and surgical CPT. Regression models were developed to predict eight outcomes, including cardiovascular morbidity, based on the preoperative risk factors. This overall rate of cardiac morbidity and mortality can then be utilized in the algorithm proposed by the guidelines.

  Table 69.2

  American College of Surgeons National Surgical Quality Improvement Project Variables Used in Universal Surgical Risk Calculators

  Modified from Bilimoria, K. Y., Liu, Y., Paruch, J. L., Zhou, L., Kmiecik, T. E., Ko, C. Y., et al. (2013). Development and evaluation of the universal ACS-NSQIP surgical risk calculator: a decision aid and informed consent tool for patients and surgeons. Journal of the American College of Surgeons, 217 , 833–842.e1–3.

  VARIABLE	CATEGORIES
  Age group, years	<65, 65–74, 75–84, ≥85
  Sex	Male, female
  Functional status	Independent, partially dependent, totally dependent
  Emergency case	Yes, no
  ASA class	1 or 2, 3, 4, or 5
  Steroid use for chronic condition	Yes, no
  Ascites within 30 days preoperatively	Yes, no
  System sepsis within 48 hours preoperatively	None, SIRS, sepsis, septic shock
  Ventilator dependent	Yes, no
  Disseminated cancer	Yes, no
  Diabetes	No, oral, insulin
  Hypertension requiring medication	Yes, no
  Previous cardiac event	Yes, no
  Congestive heart failure in 30 days preoperatively	Yes, no
  Dyspnea	Yes, no
  Current smoker within 1 year	Yes, no
  History of COPD	Yes, no
  Dialysis	Yes, no
  Acute renal failure	Yes, no
  BMI class	Underweight, normal, overweight, obese 1, obese 2, obese 3

  ASA, American Society of Anesthesiologists; BMI, body mass index; COPD, chronic obstructive pulmonary disease; SIRS, systemic inflammatory response syndrome.

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