Preoperative Evaluation of Cardiac Risk Perform Modified Cardiac Risk Index Class II Class I (20-30 pts) or (< 15 pts) Class III (> 30 pts) Look at low risk variables High risk (> 15%) see next page0-1 factor > 2 factors IntermediateLow risk risk (< 3%) (3-15%) Nonvascular Vascular surgery surgery Perform Stress thallium No further testing or Dobutamine echo Negative: Positive: SURGERY Low risk High risk
High risk patients Determine the nature of risk Sean P. Ryan, MD Preoperative Evaluation of Cardiac Risk Largely due to I. Burden of illness. modifiable factors More than 25 million patients have noncardiac surgery each year. due to A. Largely (e.g.,CHF, arrhythmia, unmodifiable risk factors valvular disease) The complication rate is significant-- data from a study of veterans shows: B. 1. 9.5% of patients had respiratory complications. 2. 4.5% of patients had cardiac complications (MI, CHF, cardiac arrest). 3. 3.1% died within 30 days of the procedure (most from noncardiac events). C. Cardiac risk is higher Largely due for patients undergoing vascular surgery: 1. 3.1% to ischemic heart disease chance of MI. 2. 5.2% chance of death. 3. Vascular patients have ~60% prevalence of asymptomatic coronary disease. II. Clinical Assessment: what can the history and physical tell us? A. Historical aspects. 1. The American Society of Anesthesiologists Score was the first clinical indexOptimize and reassess developed to predict risk. cardiac risks a. It is subjective in nature, but is still sensitive to risk. b. Its performance is less than that of other risk Patient eligible for indices. CABG independent of 2. Goldman published the original and classic multivariate model of cardiac risk in 1977. noncardiac surgery? a. This study looked retrospectively at 1001 patients undergoing non- vascular surgery. b. It identified variables which placed patients at higher risk of Yes perioperative cardiac events.No c. Based on the presence of(prophylactic CABG were assigned to 4 these variables, patients classes with different risk (Class I, lowbenefit)Class IV, high risk). of no proven risk to d. This study excluded patients with angina. Sequence CABG 3. In 1986 Detsky published a modified cardiac risk index. and noncardiac a. This added the variables of angina and remote MI. Consider cancelling surgery by b. This index improved predictive accuracy or modifying patients. among higher-risk relative urgency noncardiac surgery 4. In 1989 Eagle published an index designed to assess cardiac risk in vascular of each patients. B. Based on the above studies (and others), the ACP now recommends a modified approach to risk stratification. 1. All patients should be screened by the modified Cardiac Risk Index (Table 1).
2. Class II or III on this index predicts a high risk for perioperative cardiac events (10-15%). 3. Class I scores unfortunately do not reliably identify patients at low risk for complications. 4. These Class I patients should therefore be further stratified by Αlow risk variables≅ (see Table 2): a. If the patients have 0-1 factors, they are truly at low risk (<3%) of perioperative cardiac events. b. If the patients have 2 or more factors, they are at intermediate risk (3-15%) and may benefit from further testing (see below).III. Further Testing: how good are the tests and who should get them? A. The tests. 1. Evaluation of LV function. a. Radionuclide angiography does not discriminate risk well, either alone or combined with other noninvasive methods. b. Transthoracic echocardiogram likewise does not improve on the clinical exam for predicting postoperative MI and cardiac death. 2. Exercise stress testing. a. A significant proportion of patients undergoing vascular surgery cannot walk on a treadmill (30-70%). b. Many other patients have conditions that impair walking ability (hip or knee disease, CVA). c. Large studies show poor positive and negative predictive values for patients that can adequately perform the test. 3. Pharmacologic stress testing. a. Dipyridamole thallium. 1. All studies in patients undergoing non-vascular surgery have been of poor quality and have shown no predictive power. 2. In patients undergoing vascular surgery, this test can add risk discrimination to patients at intermediate risk: a. Negative test: LR 0.12, post-test probability 1%. b. Positive test: LR 3.02, post-test probability 23%. b. Dobutamine echocardiography. 1. Again, all studies in patients undergoing non-vascular surgery are of weak quality and show no predictive power. 2. In vascular patient with intermediate risk the test was good: a. Negative test: LR 0.0 (i.e., no events in the study). b. Positive test: LR 3.00-4.76. c. Other studies. 1. Ambulatory ECG to monitor for silent ischemia did not show strong results. 2. Cardiac catheterization has not been studied as a risk predictor.IV. Management strategies: what to do after classifying risk. A. Impact of stratification.
1. About 10% of all patients will be classified as high surgical risk by clinical evaluation. 2. Another 9-20% of patients undergoing vascular surgery will be reclassified as high risk after non-invasive testing. 3. Since no non-invasive test reliably alters risk classification in non-vascular patients, there is no conclusive data about these patients.B. For high risk patients: 1. If the patient has an unstable coronary syndrome, proceed directly to coronary catheterization (do not pass GO!, do not collect $200-- unless you=re the cardiologist!!). 2. If the patient is not a candidate for coronary revascularization, either: a. Delay the upcoming operation, if the patient=s condition can be improved, or b. Cancel the operation, if the risk of the cardiac condition outweighs the risk of the surgical condition. 3. Coronary revacularization (i.e., CABG) as a preventive step to reduce cardiac risk before surgery has not been studied prospectively. a. A large retrospective study suggests any benefit from decreased cardiac risk is offset by the risk of angiography and CABG. b. Two decision analysis models suggest no net benefit. 4. Coronary revascularization (i.e., CABG) should be performed in those patients who would meet criteria in the non-operative setting, i.e.: a. Unstable angina refractory to medical management; b. Left main coronary stenosis; c. 3 vessel disease and impaired LV function; d. 2 vessel disease with proximal LAD involvement. 5. PTCA has not been well studied in the peroperative setting.C. Other strategies. 1. Beta blockers. a. These decrease cardiac morbidity and mortality in patients with CAD or at risk for CAD: 1. 8% absolute decrease in mortality at 6 months. 2. 15% absolute decrease in combined cardiac end points. b. Patients considered at risk for coronary disease had > 2 of: 1. 65 yo or older; 2. Hypertension. 3. Current smoking. 4. Total cholesterol > 240 mg/dl; 5. Diabetes mellitus. c. The protocol was: 1. 5 mg atenolol IV 30 min before surgery and immediately after surgery. 2. Atenolol PO after surgery (100 mg if HR >65, 50 mg if HR 55-64) or 5mg IV q12h if could not take PO. 3. Hold atenolol if HR < 55 or SBP < 100mm Hg. 4. Give atenolol until hospital discharge. 2. Pulmonary artery catheterization.
a. This has not been definitively proven to be helpful. b. It is recommended on the basis of Αexpert opinion≅ in patients at high risk for hemodynamic compromise. 3. Other medical therapies (e.g., digitalis, calcium channel blockers) have not been shown to be helpful.Table 1: Modified Cardiac Risk IndexVariable PointsCoronary artery disease MI < 6 months ago 10 MI > 6 months ago 5Canadian Cardiovascular Society angina classification Class III (angina with < 1 flight of stairs) 10 Class IV (angina with any exertion) 20Alveolar pulmonary edema Within one week 5 10 Ever 5Suspected critical aortic stenosis 20Arrhythmias Rhythm other than sinus or PACs on ECG 5 > 5 PVCs on ECG 5Poor general medical status(PO2< 60, PCO2 >50, K+<3.0, BUN>50, Cr>3.0, bedridden) 5Age > 70 years 5Emergency surgery 10Class I = 20 points; Class II = 20-30 points; Class III = > 30 points.
Table 2: Low Risk VariablesCriteria of Eagle et al.Criteria of Vanzetto et al.Age > 70 years Age > 70 yearsHistory of angina History of anginaDiabetes mellitus Diabetes mellitusQ waves on ECG Q waves on ECGHistory of ventricular ectopy History of MI ST segment ischemic abnormalities on resting ECG HTN with severe LVH History of CHFReferencesACP. Guidelines for assessing and managing the perioperative risk from coronary artery diseaseassociated with major noncardiac surgery. Annals of Internal Medicine. 1997;127: 309-312. The guidelines on which this handout is based.Detsky AS et al. Predicting cardiac complications in patients undergoing noncardiac surgery.JGIM. 1986;1: 211-219. Improved upon the Goldman criteria.Eagle KA et al. Combining clinical and thallium data optimizes preoperative assessment ofcardiac risk before major vascular surgery. Annals of Internal Medicine. 1989;110: 859-866. A solid study which yielded Αlow risk≅ criteria.Goldman L et al. Multifactorial index of cardiac risk in noncardiac surgical procedures. NEJM.1977;297: 845-850. A classic study.Mangano DT et al. Effect of atenolol on mortality and cardiovascular morbidity after noncardiacsurgery. Multicenter Study of Perioperative Ischemia Research Group. New England Journal ofMedicine. 1996;335: 1713-1720. Impressive data with atenolol in patients at risk for coronary disease.Palda VA and Detsky AS. Perioperative assessment and management of risk from coronary
artery disease. Annals of Internal Medicine. 1997;127: 313-328. The accompanying data for the above guidelines.Vanzetto G et al. Additive value of thallium single photon emission computed tomographymyocardial imaging for prediction of perioperative events in clinically selected high cardiac riskpatients having abdominal aortic surgery. American Journal of Cardiology. 1996;77: 143-148. Parallels the study by Eagle, with similar risk criteria.