The importance of the appropriate perioperative cardiac management in non-cardiac surgery lies in the high number of surgical procedures performed each year and the related cardiac complications, which account for almost half of the perioperative morbidity.[1] The risk of complications in non-cardiac surgery depends on (1) the type, urgency, and duration of the surgery, and (2) the patient risk factors, including the perioperative condition and comorbidities. Perioperative cardiac management is a process of risk stratification and mitigation and not "cardiac clearance" as is often requested by providers.

Type of Surgery

Regarding cardiac risk, surgical and endovascular procedures may be classified into three categories according to the estimated 30-day cardiac event rates (cardiac death and myocardial infarction) without considering the patient's comorbidities[2]:

Low-Risk (Less Than 1%)

• Dermatological
• Dental
• Ophthalmologic
• Vascular: Carotid artery stenting and carotid endarterectomy in asymptomatic patients
• Urological: Minor surgery, transurethral resection of the prostate
• Gynecological: Minor surgery, breast surgery
• Orthopedic: Minor surgery (e.g., meniscectomy)
• Reconstructive surgery
• Thyroid surgery

Intermediate-Risk (Between 1% to 5%)

• Abdominal: Cholecystectomy, hiatal hernia repair, splenectomy
• Vascular: Carotid artery stenting and carotid endarterectomy in symptomatic patients, peripheral artery angioplasty, endovascular aneurysm repair
• Urological: Major surgery including renal transplantation
• Gynecological: Major surgery
• Neurological: Major surgery (spine)
• Orthopedic: Major surgery (hip)
• Head and neck surgery

High-Risk (Over 5%)

• Vascular: Aortic surgery, lower limb revascularization or amputation, thromboembolectomy
• Thoracic: Esophagectomy, pneumonectomy, lung transplantation
• Abdominal: Repair of a perforated bowel, pancreatic surgery, bile duct surgery, liver resection, liver transplantation.
• Urological: Total cystectomy
• Adrenal resection

It is worth noting that procedures involving a laparoscopic approach may be associated with cardiovascular complications, so these patients should undergo a preoperative risk assessment.[3]

Evaluation of Patient-Related Risk Factors

The preoperative cardiac evaluation must be tailored to each particular patient, surgical type, and urgency. History-taking and examination as a first step, including the assessment of functional capacity and risk indices, will allow the practitioner to determine the extent of preoperative cardiac evaluation. Bear in mind that ancillary exams should only be requested if the results would influence patient management. Most "low perioperative cardiac risk" patients can undergo low- and intermediate-risk surgery with only a clinical assessment.

Functional Capacity

• The evaluation of functional capacity is an important item in the preoperative cardiac risk assessment and is measured given the daily activities or, more objectively, in metabolic equivalents (METs). One MET corresponds to the basal metabolic rate of an average adult.
• The inability to climb 2 flights of stairs or run a short distance (less than 4 METs) shows low functional capacity and may predict survival after lung resection and complications after major non-cardiac surgery.[4] Conversely, when functional capacity is high, the prognosis is promising, even in a patient with stable ischemic heart disease or risk factors.[5] Most highly functional asymptomatic patients do not require further cardiovascular testing.

Calculation of Surgical Risk

A validated risk-prediction tool can predict the risk of perioperative major adverse cardiac events (MACE) in patients undergoing non-cardiac surgery.[3][6] Current risk prediction tools used include:

• Revised Cardiac Risk Index (RCRI) or the Lee risk index is the most used. It was designed in 1999 to predict myocardial infarction, pulmonary edema, ventricular fibrillation or cardiac arrest, and complete atrioventricular block. It operates with six risk factors: surgical type, ischemic heart disease history, heart failure history, cerebrovascular disease history, preoperative therapy with insulin, and creatinine greater than 170 mmol/L (greater than 2 mg/dl).[7]
• American College of Surgeon's tool predicts risk for myocardial infarction and cardiac arrest. Its development was based on data from 2007, and it identified five predictors: type of surgery, functional status, elevated creatinine (greater than 130 mmol/L or greater than 1.5 mg/dl), the American Society of Anesthesiologists (ASA) class, and the age.  It seems to have a better performance than the Lee index but does not predict some significant complications such as pulmonary edema and complete heart block.[8]
• The most recent surgical risk calculator developed by The American College of Surgeons was introduced in 2013 and is available online. It predicts complications and perioperative death and requires the typing of a high number of risk factors to be calculated, including 21 patient specifics.[9]

Biomarkers

Several studies have examined the potential utility of including biomarkers to improve the prediction of preoperative risk. The following are the most used biomarkers:

• Cardiac troponins T and I for myocardial ischemia and damage
• C-reactive protein for inflammation
• B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP) for ventricular function

The existing preliminary evidence shows that the increase in troponin T in the perioperative period reflects clinically significant myocardial damage associated with poor cardiac prognosis and surgical outcomes.[1][10] Some studies have shown that high preoperative BNP and NT-proBNP values have independent prognostic significance to predict cardiac events and long-term mortality after non-cardiac vascular surgery.[11][12] Thus, with the current evidence, the preoperative assessment via biomarkers for patients undergoing non-cardiac surgery cannot be recommended for screening in all patients but these can be considered for high-risk patients (functional capacity less than 4 METs or with an RCRI value greater than 1 for vascular surgery and greater than 2 for non-vascular surgery).

Non-Invasive and Invasive Testing

Myocardial ischemia, valvular heart disease, and ventricular dysfunction are known major determinants of surgical risk. Preoperative non-invasive and invasive testing may be helpful for diagnosis in patients with strong clinical suspicion or to improve the condition in patients with known cardiac diseases. The investigation should be carried out as in patients who will not undergo surgery and should only be undertaken if the expected outcome would change perioperative management or help inform the patient about their options.

Risk-Reduction Strategies: Perioperative Medical Therapy

Beta-Blockers

The evidence currently available shows that the preoperative use of beta-blockers was associated with a reduction in cardiac events but not in surgical death.[13] In addition, preoperative use was associated with arterial hypotension, bradycardia, and stroke.[14][15] Therefore, the following recommendations are made[3][6]:

• Patients undergoing surgery who have been on beta-blockers chronically should continue use. It should be noted that in a national cohort study, patients with uncomplicated arterial hypertension that received 2 drugs until surgery, including a beta-blocker, suffered higher cardiac mortality, infarction, and stroke rate.[16]
• In patients with an intermediate or high risk of developing myocardial ischemia or with 3 or more RCRI risk factors, it may be reasonable, to begin with, beta-blockers in the preoperative period. Atenolol or bisoprolol should be considered as a first-choice drug.[17][18]
• Regardless of whether the patient was previously using beta-blockers, administration after surgery may be justified due to clinical needs.
• In patients with obstructive pulmonary disease who need it, cardioselective beta-blocker therapy is not contraindicated.[19][20]

Perioperative Statin Therapy

Statins, in addition to their effect on lipids, induce coronary plaque stabilization through pleiotropic effects. This may prevent plaque rupture and subsequent myocardial infarction in the perioperative period. Preliminary evidence supports that preoperative statin use in non-cardiac surgery may decrease mortality and myocardial injury.[21] Besides, some studies have shown that the preoperative statin therapy interruption in a patient within 2 years following stent placement or immediately after aortic surgery may increase the mortality and myocardial injury, respectively.[22][23] Therefore, the following recommendations are made[3][6]:

• The patients that will undergo surgery who have been on statins chronically should continue its use.
• Preoperative initiation of statin use may be reasonable in patients undergoing vascular surgery and in patients with clinical indications who are undergoing high-risk procedures.
• If statins are being used during the perioperative period, long half-life or extended-release formulations should be administered preoperatively, since there are no parenteral formulations to use immediately after surgery.
• Ideally, preoperative therapy with the statin should begin at least two weeks before surgery to detect any adverse effect of the drug before surgery.

Calcium Channel Blockers

Further evidence is needed to define the value of these drugs during the perioperative period of non-cardiac surgery. Calcium channel blockers should be continued during the perioperative period in patients with vasospastic angina.[3] Heart rate-reducing calcium channel blockers may be considered in patients with beta-blockers adverse effects unless they have a contraindication.[3]

Angiotensin-Converting Enzyme Inhibitors (ACEIs) and Angiotensin-Receptor Blockers (ARBs)

Currently, there is no significant evidence showing the benefit of continuing the administration of ACEIs or ARBs to patients who will undergo a non-cardiac surgery.[24] The perioperative use of ACEIs or ARBs increase the arterial hypotension risk, and a recent cohort study showed that withdrawal before surgery reduced mortality, stroke, and myocardial injury.[25][26] Therefore, whether the preoperative use of these drugs should be continued or discontinued remains debatable until more evidence is available. If discontinued, the morning before surgery is sufficient time, and it could be resumed after surgery as soon as blood volume and pressure are stable.

Antiplatelet Agents

In patients with coronary stents or those who have suffered acute coronary syndrome (ACS), the early discontinuation of double antiplatelet therapy (DAPT) significantly increases the risk of thrombosis, and therefore, acute coronary events.[27] In patients with a known cardiovascular disease or a high risk to develop it, even if they do not have coronary stents, the withdrawal of antiplatelet therapy may be associated with the appearance of new cardiac events.[28][29][30] On the other hand, the risk of perioperative bleeding is greater in patients who continue to receive aspirin and even higher with DAPT.[6][31] Therefore, the following recommendations are made:

• If possible, in patients with coronary stent placement without ACS within the last year, the surgery should be rescheduled so they receive DAPT during six weeks for the bare-metal stent and for at least 4 months, or ideally 6 months, for the drug-eluting stent. Afterward, P2Y-inhibitor should be discontinued for a week, and if feasible, all patients should continue with aspirin and resume DAPT as soon as possible after surgery.[32]
• Elective surgery should be delayed for at least 12 months in patients who suffered an ACS, and the DAPT should be continued throughout that period, regardless of ACS therapy used. Afterward, P2Y-inhibitor should be discontinued for one week, and if feasible, all patients should continue with aspirin and resume DAPT as soon as possible after surgery.[32]
• In the cases mentioned above, whenever the surgery cannot be rescheduled, DAPT should be continued through the perioperative period unless the complications of risk due to bleeding outweighs the risk of a major cardiac adverse event (e.g., major, active, life-threatening bleeding; intracranial, spinal or posterior chamber of the eye surgery).[32]
• Initiation of aspirin therapy within 4 hours of non-cardiac surgery and continuation during the perioperative period in patients who do not receive aspirin, with previous coronary stent placement (more than 6 weeks for bare-metal and more than one year for drug-eluting) seems to reduce the risk of death and myocardial infarction but increases the risk of bleeding.[33]
• Discontinuation of aspirin for at least 1 week before a procedure is recommended in patients without the cardiovascular disease to undergo elective non-cardiac surgery unless the risk of cardiac events outweighs the risk of bleeding.[34]
• Initiation or continuation of aspirin therapy may be reasonable in patients with cardiovascular disease who have not had coronary stent placement but have an elevated risk of cardiac events unless the type of surgery they will undergo has a significant increase in severe complications due to the increased risk of bleeding (e.g., intracranial surgery, spinal surgery, transurethral prostatectomy).[3][6][28][29][30]
• For patients who need interruption of antiplatelet therapy, it should be 5 days before the surgery for clopidogrel or ticagrelor and 7 days for aspirin and prasugrel. Avoid the use of low-molecular-weight heparin for bridging in these patients.[3]

Anticoagulants

Thromboembolic risk and the risk of bleeding relative to the type of surgery to be performed should be weighed in each patient treated with anticoagulants. In high thromboembolic risk cases with a low risk of surgical bleeding (e.g., skin surgery), anticoagulant therapy may not be discontinued. In surgeries with a high risk of bleeding, anticoagulant therapy should be discontinued. In these cases, if there is a patient with a high risk of thromboembolic complications, the anticoagulants should be dosed so that the effect remains only until a few hours before surgery.

Risk-Reduction Strategies: Preoperative Cardiac Surgery and Endovascular Procedures

Coronary Revascularization[3][6]

Indications for surgical or endovascular coronary revascularization in the preoperative period of a non-cardiac surgery are like those in the non-surgical setting. Control of myocardial ischemia before non-cardiac surgery is recommended whenever the operation can be delayed at no risk for the patient. Routine myocardial revascularization in patients without myocardial ischemia is not recommended before non-cardiac surgery exclusively to reduce the risk of perioperative cardiac events.

Interventions on the Heart Valves[6][35]

Since the following valvular heart diseases increase the perioperative risk of cardiac events in non-cardiac surgery, it is reasonable to treat them in advance of non-cardiac surgery to reduce the risk whenever the level of severity mentioned below is reached.

• Aortic stenosis: In patients with severe aortic stenosis, urgent non-cardiac surgery should be performed under careful hemodynamic monitoring. In symptomatic patients with severe aortic stenosis that need elective non-cardiac surgery, valve replacement should be considered first. In this group of patients, aortic balloon valvuloplasty or transcatheter aortic valve implantation may be considered in those at high risk for a valvular surgery, 
• Mitral stenosis: Patients with severe mitral stenosis, symptomatic, or with a systolic pulmonary artery pressure greater than 50 mmHg should undergo valvular surgery or percutaneous mitral commissurotomy before non-cardiac surgery if it is a high-risk one.
• Aortic and mitral regurgitation: In patients with severe mitral or aortic regurgitation, symptomatic or with ventricular dysfunction, valvular surgery should be considered previous to the non-cardiac surgery.

The clinical significance of the proper perioperative cardiac management in non-cardiac surgery lies in the high number of surgical procedures performed each year and the related cardiac complications. Before surgery, the health professional must assess the risk of surgery type and the patient's risk. The patient's risk can be specified through history, examination, and non-invasive and invasive tests. The evaluation of functional capacity and the calculation of surgical risk may be useful in this regard. The preventive approach is pivotal, and if the situation warrants it, risk reduction strategies should be implemented with drugs, surgery, or endovascular procedures.

In patients with true life-threatening surgical issues, operative intervention should not be delayed by ticagrelor or extensive perioperative cardiac management. In patients who continue antiplatelet agents or anticoagulants in the perioperative period, a meticulous surgical technique should be employed to minimize the risk of postoperative bleeding complications.