Preoperative Cardiovascular Risk Assessment

Approximately 1.5 million patients undergo non-cardiac surgery every year in the Australia. Of those, about 2500 have a perioperative MI. Furthermore, over half of the 2000 perioperative deaths each year are caused by cardiac events. Patients over 65 years of age are at higher risk of cardiac disease, cardiac morbidity, and death. Considering that this patient population will greatly increase over the coming decades, the number of patients with significant perioperative cardiac risk undergoing non-cardiac surgery can be expected to increase globally. 

Most perioperative cardiac morbidity and mortality is related to MI, heart failure, or arrhythmias. Therefore, preoperative evaluation and perioperative management emphasise the detection, characterisation, and treatment of CAD, left ventricular (LV) systolic dysfunction, and significant arrhythmias in appropriate patients. These include patients with known or suspected CAD, arrhythmias, history of heart failure, or current symptoms consistent with these conditions. In the asymptomatic patient, a more extensive history and physical examination is warranted in people aged 50 years or older.

In addition, non-cardiovascular disease states account for a significant proportion of perioperative complications and may contribute to protracted hospital admission and long-term morbidity.

The purpose of individual preoperative cardiovascular and general medical risk assessment is to:

• Assess the medical status of the patient and the cardiac risks posed by the planned non-cardiac surgery

• Recommend appropriate strategies to reduce the risk of cardiac problems over the entire perioperative period, and to improve long-term cardiac outcomes.

The main overall goals of assessment are to:

• Identify patients at increased risk of an adverse perioperative cardiac event

• Identify patients at an increased risk of post-operative complications

• Identify patients with a poor long-term prognosis due to cardiovascular disease. Even though the risk at the time of non-cardiac surgery may not be prohibitive, appropriate treatment will affect long-term prognosis.

The nature of the evaluation should be individualised to the patient and the specific clinical scenario.

• Patients presenting with an acute surgical emergency require only a rapid preoperative assessment, with subsequent management directed at preventing or minimising cardiac morbidity and death. Such patients can often be more thoroughly evaluated after surgery.

• Patients undergoing an elective procedure with no surgical urgency can undergo a more thorough preoperative evaluation.

Stepwise management approach

The optimal perioperative outcome can be assessed as follows:

1. Assess clinical features:

• The history and physical examination should help to identify markers of cardiac risk and assess the patient's cardiac and general medical status

• The patient history should aim to:

· Identify cardiac conditions (e.g., recent or past MI, decompensated heart failure, prior unstable angina, significant arrhythmias, valvular heart disease) which are high risk

· Identify serious comorbid conditions (e.g., diabetes, peripheral vascular disease, stroke, renal insufficiency, pulmonary disease)

· Determine patient's functional capacity

· Document all current medications, allergies, tobacco use, and physical exercise habits.

• On physical examination, patients with severe aortic stenosis, elevated jugular venous pressure, pulmonary oedema, and/or third heart sound are at high surgical risk.

2. Evaluate functional status

• Patients who are able to exercise on a regular basis without limitations generally have sufficient cardiovascular reserve to withstand stressful operations.

• The functional capacity of the patient to perform common daily activities has been shown to correlate well with maximum oxygen uptake by treadmill testing. The metabolic equivalent of a task (MET) is a physiological concept expressing the energy cost of a physical activity. The MET reference values are shown below. On assessment, patients with <4 METS are considered to have poor functional capacity and are at relatively high risk of a perioperative event, while patients with >10 METS have excellent functional capacity and are at very low risk of perioperative events, even if they have known CAD. Patients with a functional capacity of 4 to 10 METS are considered to have fair functional capacity and are generally considered at low risk of perioperative events.

  = 1 MET - Eat, dress, use the toilet; Walk indoors around the house; Walk on level ground at 2 mph (3.2 km/hour); Perform light housework such as washing dishes.
  = 4 METs - Climb a flight of stairs (usually 18-21 steps); Walk on level ground at 4 mph (6.4 km/hour); Run short distances; Perform vacuuming or lift heavy furniture; Play golf or doubles tennis.

3. Consider surgery-specific risk

• The type of surgery has important implications for perioperative risk. Non-cardiac surgery can be stratified into high-risk, intermediate-risk, and low-risk categories

• High-risk surgery
  • Emergency major operations, particularly in older people (>70 years)
  • Aortic or peripheral vascular
  • Extensive operations with large volume shifts
• Intermediate-risk surgery
  • Intraperitoneal or intrathoracic
  • Carotid endarterectomy
  • Head and neck
  • Orthopaedic
  • Prostate
• Low-risk surgery
  • Endoscopic procedures
  • Superficial biopsy
  • Cataract
  • Breast.

4. Decide whether further non-invasive evaluation is needed

• Patients who are at low cardiac risk based on clinical features and functional status, and are undergoing low-risk surgery, do not generally require further evaluation.

• Patients who are at high cardiac risk based on clinical features, have poor functional status, and are being considered for high-risk non-cardiac surgery may benefit from further evaluation.

• Further risk stratification can be based on the presence or absence of clinical predictors; 

High Risk: The presence of ≥1 of the following active cardiac conditions is considered high risk, mandates intensive management, and may result in delay or cancellation of surgery unless the surgery is urgent.

• Unstable coronary syndromes : Unstable or severe angina or Recent MI
• Decompensated heart failure
• Significant arrhythmias: [Mobitz II atrioventricular block, hird-degree atrioventricular block, Symptomatic ventricular arrhythmias, Supraventricular arrhythmias (including atrial fibrillation) with uncontrolled ventricular rate (heart rate >100 bpm at rest), Symptomatic bradycardia, Newly recognized ventricular tachycardia
• Severe valvular disease : Severe aortic stenosis (mean pressure gradient >40 mmHg, aortic valve area <1.0 cm^2, or symptomatic), Symptomatic mitral stenosis (progressive dyspnoea on exertion, exertional presyncope, or heart failure).

• History of heart disease
• History of compensated or prior heart failure
• History of cerebrovascular disease
• Diabetes mellitus
• Renal insufficiency.

5. Decide on the need for preoperative cardiac testing

• Patients at low risk generally require no additional testing before non-cardiac surgery. However, those with intermediate or high risk undergoing elective non-cardiac surgery may require additional testing.
• Patients at low or high risk of an adverse perioperative cardiac event can typically be identified following history and examination. Patients at low risk generally require no additional testing before non-cardiac surgery. However, those with intermediate or high risk undergoing elective non-cardiac surgery may require additional testing.

1. Preoperative resting 12-lead ECG
2. Preoperative non-invasive evaluation of LV function using echocardiography - Reasonable or recommended for patients with:
   • ​​​​​​​​​​​​​​​​​​​​​Dyspnoea of unknown origin
   • Current or prior heart failure with worsening dyspnoea or other change in clinical status if LV function has not been assessed within 12 months
   • Known ischaemic or hypertensive heart disease
   • Known valvular heart disease
3. Stress testing
   • Useful to detect myocardial ischaemia and functional capacity
   • Indicated in patients with active cardiac conditions (e.g., unstable angina, decompensated heart failure, or severe valvular heart disease) who typically need further evaluation
   • Reasonable for patients with ≥3 clinical predictors of cardiac risk and poor functional capacity (<4 METs) who require intermediate/high risk surgery
   • Not indicated for patients undergoing low-risk non-cardiac surgery.

6. Decide when to recommend invasive evaluation:

• Indications for preoperative coronary angiography are similar to those in the non-operative setting and include patients with evidence of high cardiac risk based on non-invasive testing, angina unresponsive to adequate medical therapy, unstable angina, and proposed intermediate-risk or high-risk non-cardiac surgery after equivocal non-invasive test results.

• Angiography and revascularisation are not routinely indicated for patients with stable CAD.

7. Optimise medical therapy

• Patients should be given optimal medical therapy, both perioperatively and in the long term, based on their underlying cardiac condition.

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