| MI<6 months ago | 10 |
| MI>6 months ago | 5 |
| Class III angina | 10 |
| Class IV angina | 20 |
| Pulmonary edema within 1 week | 10 |
| h/o pulmonary edema | 5 |
| Critical aortic stenosis | 20 |
| Rhythm other than sinus or sinus plus atrial premature beats on EKG | 5 |
| >5 PVSs on EKG | 5 |
| Poor general medical status | 5 |
| Age> 70 years | 5 |
| Emergency surgery | 10 |
The modified cardiac risk index (MCRI) should be performed on all patients undergoing perioperative risk evaluation. Class II (MCRI:20-30) or III (MCRI:>30) on the MCRI predicts high risk for perioperative cardiac events (10% to 15%; strong evidence for patients having vascular surgery and those having nonvascular surgery). However, the MCRI can only reliably identify those patients who are at high risk for an event. If a patient's MCRI is below 20, the patient is either at low or intermediate risk for an event and further risk stratification must be performed using the low risk variables (see below).
| Age>70 | 1 |
| History of angina | 1 |
| Diabetes mellitus | 1 |
| Q waves on EKG | 1 |
| History of ventricular ectopy | 1 |
If the patient's MCRI is less than 20, he is either at low or intermediate risk for a cardiac event perioperatively. To determine whether he is at low or intermediate risk, you must determine the number of low risk variables the patient has. The patient gets 1 point for each low risk variable. If the patient has 0 or 1 low risk variables, then he is at low risk for a perioperative cardiac event, however, if he has 2 or more low risk variables then he is at intermediate risk for an event.
*Based on criteria of Eagle et al (Ann Intern Med. 1989;110:859-66)
Noninvasive tests available for further risk stratification include those that assess left ventricular function (radionuclide angiography), cardiac ischemia (exercise or pharmacologic stress testing electrocardiographic monitoring), or both (dobutamine stress echocardiography). A noninvasive test may be able to detect a cardiac abnormality, the presence of which does not necessarily predict increased risk. Noninvasive testing may never be able to stratify patients fully because postoperative events probably have multifactorial causes. Tests done before surgery cannot account for every intra- and postoperative factor. For example, the perioperative period is a time of hypercoagulability, catecholamine surges, pain, and operative stress, all of which may influence oxygen demand, and factors other than coronary stenosis (for example, anemia) that may influence oxygen supply, leading to myocardial ischemia.
Transthoracic echocardiography does not improve on the clinical examination in the prediction of postoperative myocardial infarction and cardiac death (strong evidence).
Exercise stress testing is a widely available and inexpensive method of screening for coronary artery disease. A substantial portion of patients with peripheral vascular disease (30 -70%) cannot attain target heart rates and therefore cannot complete the test adequately for diagnosis. Other problems, such as degenerative knee disease or previous stroke, can also impair walking ability. In patients who could perform the test, one small study of patients with vascular disease showed a predictive positive likelihood ratio of 4.83 (presence of ST-segment depression) and a predictive negative likelihood ratio of 0.00 (absence of ST-segment depression). However, other larger studies do not support these findings, showing poorly predictive positive and negative likelihood ratios.
Several prospective strong-quality and fair-quality studies have shown that dipyridamole-thallium imaging can add risk discrimination to that provided by the clinical evaluation alone for patients undergoing vascular surgery. No studies of similar quality have assessed the predictive accuracy in patients undergoing nonvascular surgery.
Stress echocardiography has the theoretical advantage of being able to assess both regional wall motion abnormalities resulting from induced myocardial ischemia and left ventricular function. The most commonly studied method is dobutamine stress echocardiography. Studies have shown that for patients undergoing vascular surgery dobutamine stress echocardiography has good predictive accuracy. Strong quality and fair quality studies assessing the predictive accuracy of stress echocardiography in patients undergoing noncardiac surgery do not exist.
It would be desirable to have a noninvasive test for intermediate-risk patients undergoing nonvascular surgery that performs as well as dipyridamole-thallium imaging and dobutamine stress echocardiography in patients having vascular surgery. Unfortunately, all studies of dipyridamole-thallium imaging and dobutamine stress echocardiography in nonvascular patients are of weak quality. Four of the five published studies in this group show poor positive and negative likelihood ratios for dipyridamole-thallium imaging in the prediction of myocardial infarction and cardiac death.
Therefore, proceeding with dipyridamole-thallium imaging or dobutamine stress echocardiography in the intermediate-risk patients having nonvascular surgery carries the risk for minor morbidity, incurs the cost of testing , and may result in unnecessary downstream interventions.
Cardiac catheterization has been recommended by some authors as a routine screening test in patients undergoing vascular surgery because these patients have a high prevalence of coronary artery disease, however, the value of angiography as a risk predictor has not been reported. Cardiac catheterization has been reported to carry a mortality rate of 0.01% to 0.5% and a rate of serious morbidity ranging from 0.03% to 0.25%.
In a randomized trial by Mangano and colleagues, perioperative B-blocker therapy was shown to reduce long-term (6-month) mortality with few side effects. Thus the ACP guidelines recommend the perioperative use of atenolol in patients with coronary artery disease (as per the criteria of Mangano and colleagues: N Engl J Med. 1996;335:1713-20).