Cardiac evaluation before non-cardiac surgery

Cardiac evaluation before non-cardiac surgery

Cardiac events are the most common serious perioperative adverse events and may occur in 1% to 5% of the persons undergoing major surgical procedures, with actual incidence depending on the preoperative cardiac status of the individual. Purpose of preoperative evaluation is not just to give medical clearance for surgery, but to have an evaluation of person’s current medical status to make perioperative recommendations on evaluation, management and risk of cardiac problems. The evaluation aims to provide a clinical risk profile to the person, non-physician caregivers, primary physician of the person, anesthesiologist and surgeon for making treatment decisions which may influence short- and long-term cardiac outcomes.

Active cardiac conditions which should be treated before non-cardiac surgery

Unstable coronary syndromes like unstable or severe angina (Class III / IV)  and recent myocardial infarction
Decompensated heart failure – Class IV, worsening or new-onset heart failure
Significant arrhythmias like high-grade AV block, Mobitz type II AV block and complete AV block, symptomatic bradycardia, symptomatic ventricular arrhythmias and supra arrhythmias with uncontrolled ventricular rate above 100 per minute
Severe valvular diseases like severe aortic stenosis and symptomatic mitral stenosis

Functional capacity

Functional capacity has an important role in deciding further evaluation. A person classified as high risk due to age or known coronary artery disease, but asymptomatic and runs for 30 minutes daily may need no further evaluation while a sedentary person with no history of cardiovascular disease but with clinical factors that suggest increased perioperative risk needs more extensive preoperative evaluation.

Important factors in the history

History of pacemaker or implantable cardioverter defibrillator implantation has to be noted as these devices need special care perioperatively. History of orthostatic intolerance may give important clues to the cardiovascular status. Any recent change in symptoms of cardiovascular disease, current medications used, including herbal and nutritional supplements, and dosages have to be documented. Use of alcohol, tobacco, and over the counter or illicit drugs have also to be noted.

Physical examination

Measurement of blood pressure, ideally in both arms, to check for any difference, checking carotid pulse contour and bruits, jugular venous pressure and pulsations are all important in preoperative cardiovascular evaluation. Precordial palpation and auscultation, auscultation of the lungs, abdominal palpation and evaluation of extremities for edema and vascular integrity are essential. Look for anemia as it can exacerbate myocardial ischemia and aggravate heart failure.

Revised cardiac risk index

Revised cardiac risk index by Lee et al [1] for the preoperative evaluation of cardiac risk is one among the several available. It comprises of six independent risk correlates:
1. Ischemic heart disease – history of myocardial infarction, positive treadmill test, use of nitroglycerin, current complaints of cardiac pain or ECG with abnormal Q waves.
2. Congestive heart failure – history of heart failure, pulmonary edema, paroxysmal nocturnal dyspnoea, peripheral edema, bilateral rales, S3, or chest x-ray with pulmonary vascular redistribution.
3. Cerebral vascular disease – history of transient ischemic attack (TIA) or stroke.
4. High-risk surgery like abdominal aortic aneurysm, other vascular, thoracic, abdominal or major orthopedic surgery.
5. Diabetes mellitus requiring preoperative insulin therapy.
6. Preoperative serum creatinine more than 2 mg per deciliter.

Minor predictors of cardiac risk

These are some recognized markers for cardiovascular disease like advanced age (more than 70 years), abnormal ECG features like left ventricular hypertrophy, left bundle branch block, ST segment and T wave abnormalities, rhythm other than sinus and uncontrolled systemic hypertension.

Classification of functional capacity

Functional capacity can be classified as follows:
Excellent : > 10 METs
Good : 7 to 10 METs
Moderate : 4 to 7 METs
Poor : < 4 METs
Unknown (cannot be assessed due to other factors which prevent assessment of functional capacity)
One MET or metabolic equivalent is the basal metabolic requirement of an individual which comes to 3.5 ml oxygen per kilogram per minute.

Supplemental preoperative evaluation

Assessment of risk for coronary artery disease and functional capacity can be done with a combination of 12-Lead ECG and exercise stress testing. Pharmacological stress testing is considered when exercise stress testing is not clinically feasible. Avoid stress testing in unstable patient, consider coronary angiography if indicated.
Assessment of left ventricular function can be done by echocardiography which is widely available and more economical or rarely by radionuclide ventriculography or contrast ventriculography.

Please note that emergency surgery for life threatening conditions should not be deferred just because of perceived cardiovascular risk.

Reference

1. T H Lee, E R Marcantonio, C M Mangione, E J Thomas, C A Polanczyk, E F Cook, D J Sugarbaker, M C Donaldson, R Poss, K K Ho, L E Ludwig, A Pedan, L Goldman. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation. 1999 Sep 7;100(10):1043-9.