Cardiovascular complications are one of the most common causes of perioperative adverse events in patients who undergo noncardiac surgery and have been estimated to be associated with a mortality rate as high as 70%.1,3 It is critical for clinicians to understand the importance of evaluating preoperative cardiac risk in noncardiac surgery patients. The whole point of preoperative cardiac assessment is to understand the patient’s cardiac conditions, determine the risk that the specific surgery planned poses as well as determine whether an intervention is warranted to decrease the patient’s perioperative risk.4
Ischemic heart disease is a major predictor of cardiovascular complications. It is defined as a history of current angina, history of myocardial infarction, use of sublingual nitroglycerin, the presence of Q waves on an electrocardiogram, positive exercise test results. Cerebrovascular disease is defined as a history of a prior stroke or a prior transient ischemic attack.
Some patients are at intermediate risk or high-risk for surgery and therefore require a more thorough clinical evaluation before they undergo major surgical procedures. High-risk surgical procedures are defined as intrathoracic, intraperitoneal and supra inguinal vascular procedures. Often, physicians evaluate these patients with a screening questionnaire which may then trigger a more comprehensive evaluation. Comprehensive evaluation usually involves a thorough history and physical with a specific focus on occult cardiopulmonary diseases.4
Symptoms of cardiovascular disease include shortness of breath, chest pain at rest, anginal equivalent symptoms, claudication, syncope and presyncope. Worsening exercise intolerance is a good predictor of overall perioperative risk especially in patients who self-report cardiopulmonary symptoms which are exercise induced.
Energy used by muscles either at rest or during activity is expressed as a function of the total body oxygen uptake (VO2). VO2 has been shown to be equal to the product of the cardiac output and the oxygen extraction in the peripheral tissues. The result of this product is defined as metabolic equivalent (MET) levels. A MET level 1 defined as the energy expended at rest which is approximately 3.5mlO2/kg body weight/min. Essentially, this is a convenient way of expressing energy spent during activity compared to energy spent at rest. MET activity levels are based on age, sex, exercise habits and cardiovascular levels. Of note, the metabolic equivalent level is defined as oxygen consumption of a 70 kg man at rest.5
Poor exercise tolerance as it pertains to predicting perioperative events is defined as an inability to climb two flights of stairs or walk four blocks at a normal pace. In addition, it is defined as an inability to meet a metabolic equivalent (MET) level of 4.
Every patient who is scheduled for a major surgery does not require preoperative noninvasive cardiac evaluation. Most clinical providers use a risk stratification model based on clinical parameters. Patients with a high cardiac risk index should be sent for further evaluation, and the need for revascularization should be carefully considered. Noninvasive cardiac testing consists of a measurement of blood pressure and heart rate, electrocardiography, exercise and pharmacologic stress test. Occasionally, providers choose to use medications for preventive measures in the preoperative setting. Some examples include; statins, antiplatelet agents, beta blockers and alpha agonists with the goal being to reduce adrenergic stimulation, inflammation and ischemia in the perioperative setting.4