Pre Operative Cardiac Evaluation! Dr. Abhijit Nair Consultant Anesthesiologist Care Hospital, Hyderabad
Goals : To identify patients at risk through history, physical examination & ECG. To evaluate the severity of underlying cardiac disease through cardiac tests. Stratify the extent of risk & determine the need for preoperative interventions to minimize risk of peri operative complications.
Major hemodynamic stress, Changes in cholinergic activity, Changes in catecholamine activity, Body temperature fluctuations, Pulmonary function is altered, Fluid shifts, Pain. Why is there perioperative risk?
The initial history, physical examination, and electrocardiogram assessment should focus on identification of potentially serious cardiac disorders. In addition to identifying the presence of pre-existing manifested heart disease, it is essential to define disease severity, stability, and prior treatment.
Decreased systemic vascular resistance, Decreased stroke volume, Induction of general anesthesia lowers systemic arterial pressures by 20-30%, tracheal intubation increases the blood pressure by 20-30 mm Hg, and many anesthetic agents lower cardiac output by 15%. Risks of anesthesia :
Other factors that help determine cardiac risk include functional capacity, age, co morbid conditions (e.g., diabetes mellitus, peripheral vascular disease, renal dysfunction, and chronic pulmonary disease).
The type of surgery (vascular procedures and prolonged, complicated thoracic, abdominal, and head and neck procedures ) are considered higher risk.
The presence of anemia may also place a patient
at higher perioperative risk.
Numerous risk indices have been developed over the years on the basis of multivariate analyses. In addition to the presence of CAD and HF, a history of cerebrovascular disease, preoperative elevated creatinine greater than 2 mg per deciliter, insulin treatment for diabetes mellitus, and high-risk surgery have all been associated with increased perioperative cardiac morbidity. ( By Lee et all in 1999 in Revised Cardiac Risk Index).
Evaluation of cardiac risk : The cornerstone of preoperative cardiac evaluation includes :- - review of history , - physical examination, - diagnostic tests, - knowledge of the planned surgical procedure.
HISTORY : Risk factors : Age, HTN, DM, Dyslipidemias, Smoking. Angina : Stable/ unstable, present medications. Previous MI : How was it? MI : NYHA,PH, Pulmonary edema. Dysrhythmias : Palpitations. Associated CVS disease : Carotid, cerebral, aortic, PVD. 7) Presence of pacemaker/ ICD.
Physical examination : General examination : Cyanosis, pallor, dyspnea during conversation or with minimal activity, poor nutritional status, obesity, skeletal deformities, tremor & anxiety are just a few of the clues of underlying disease or CAD. 2) Vitals : Pulse, BP , Pulse pressure, Respiration.
The metabolic equivalent, or MET, is defined as the ratio of a person's working metabolic rate relative to the resting metabolic rate. One MET represents the oxygen consumption of a resting adult (3.5 ml/kg/min). In the Revised cardiac risk index by Lee et al functional status was not independently associated with risk. If patients reduce exertion because of cardiac symptoms but still meet a 4-MET threshold, clinicians will underestimate risk. Conversely, non cardiac functional limitations (e.g., knee or back pain) may falsely overestimate cardiac risk.
Functional capacity is defined as : poor (<4 METS), moderate (4–7METS), good (>7–10METS) , based on evaluation of the patient’s daily activity. Measurements on a treadmill inducing ischemia at low-level exercise (<5 MET or heart rate <100 /min) identifies a high-risk group, whereas the achievement of more than 7 MET (or heart rate >130 / min) without ischemia identifies a low-risk group.
The ECG is frequently obtained as part of a preoperative evaluation in all patients over a specific age or undergoing a specific set of procedures.
Metabolic & electrolyte disturbances, medications, intracranial disease, pulmonary disease can alter ECG.
Conduction disturbances (RBBB) or first-degree AV block, may lead to concern but usually do not justify further workup.
Preoperative resting electrocardiogram is readily available, inexpensive, easy to perform and able to interpret and detect previous myocardial infarction, acute ischemia, or arrhythmias. The presence of abnormalities such as Q waves and non sinus rhythms has been shown to correlate with adverse postoperative cardiac events.
RISK INDICES : ASA. NYHA/CCS. Goldman ( 1977). Detsky (1997 ). ACC / AHA ( Updated in 2007 ). ACP. Lee ( 1999 ). Cooperman ( 1978 ). Larsen( 1987 ). Pedersen ( 1990 ). Vanzetto ( 1996 ).
ASA – used for assessment of the patient’s overall physical status and to predict morbidity & mortality. NYHA/CCS - used for risk stratification of medical patients with angina, but they have been adapted for use in surgical patients. Cardiac Risk Index (CRI) by Goldman et al identified9 independent variables that correlated with adverse perioperative events.
The ACC/AHA guidelines provide a framework for screening and identifying patients who are at high risk for perioperative cardiac events (PCE).
The accuracy of any of the above risk indices is controversial. A cardiac risk index to be useful, has to be applicable to all and be consistently accurate. They couldn’t be applied to all surgeries. They were at times cumbersome to apply. Non prospective.
High-grade AV block. Symptomatic ventricular arrhythmias in the presence of underlying heart disease. Supraventricular arrhythmias with uncontrolled ventricular rate.
Severe valvular disease
Intermediate clinical predictors – Mild angina, Prior MI by history or pathologic Q waves, compensated or prior CHF, diabetes mellitus, renal insufficiency. Intermediate Predictors
Minor : Advanced age, Abnormal ECG (LVH,LBBB, ST-T abnormalities), Rhythm other than sinus (e.g. AF), Low functional capacity (e.g., inability to climb one flight of stairs), History of stroke, Uncontrolled systemic hypertension.
Surgical Risk High Risk : >5% risk of perioperative death or MI . emergent major surgery, peripheral vascular or aortic surgery, prolonged surgery involving excessive blood loss. Moderate Risk : 1-5% risk of perioperative death or MI . Carotid end arterectomy and urologic, orthopedic, uncomplicated abdominal, head, neck, and thoracic operations Low Risk : <1% risk . Cataract removal, endoscopy, superficial procedure, cosmetic procedures, and breast surgery Fleisher, et al. ACC/AHA 2007 Guidelines on Perioperative Cardiovascular Evaluation and Care for Noncardiac Surgery: Executive Summary. Circulation. 2007;116:1971-1996.
Algorithm(ACC/AHA) for stepwise approach onperioperative evaluation
Indications for preoperative cardiac testing : 1. Patients with intermediate clinical predictors. 2. Prognostic assessment of patients undergoing initial evaluation for suspected or proven CAD. 3. Evaluation of patients with change in clinical status. 4. Evaluation of adequacy of medical treatment 5. Prognostic assessment after an acute coronary syndrome.
Risk reduction strategies : Perioperative management :- a. Anesthetic techniques. i. General versus regional anesthesia , ii. Temperature regulation , iii. Invasive monitoring – PAC, TEE. b. Surgical approach. i. Laparoscopic, endovascular procedures.
2. Medical management :- a. Beta blockers. b. Other anti-ischemic medications. c. Statins. 3. Preoperative coronary revascularization / valvuloplasty.
Preoperative coronary angiogram / coronary intervention: CLASS I:- 1. patients with stable angina who have significant LMCA stenosis. 2.patients with stable angina who have 3-vessel disease. (Survival benefit is greater when LVEF is less than 0.50.) 3. patients with stable angina who have 2-vessel disease with significant proximal LAD stenosis and either EF less than 0.50 or demonstrable ischemia on noninvasive testing. 4. for patients with high-risk unstable angina or non– ST segment elevation MI. 5. Coronary revascularization before noncardiac surgery is recommended in patients with acute ST-elevation MI. ( All have level of evidence A).
Conclusion : Thorough history, Detailed physical examination, Judicious use of tests. Categorize patients into low, intermediate & high risk category . Combine preop assessment with periop risk reduction strategies & optimize medical treatment to improve outcome.
My references : ACC/AHA 2007 Guidelines on Perioperative Cardiovascular Evaluation and Care for Noncardiac Surgery. Preoperative Assessment of Cardiac Risk by Emmanuel Rupert, IJA 2007; 51 (4) : 269-278.