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What test should be performed?


It is important to understand that the risk indices perform best when coupled with the results of preoperative cardiac testing. The ACC/AHA guidelines suggest that the best test is an exercise EKG. However, the demonstration of ST depression in women is not as sensitive or specific as it is in men. In addition, as many as 30% of patients coming for exercise EKG have resting abnormalities (ST changes, bundle branch blocks, pacemakers, etc.) which render the test non-specific. Finally many patients cannot perform an exercise test since they have orthopedic, peripheral vascular or cardiac limitations. To circumvent these particular problems, the ACC/AHA guidelines suggest the use of Persantine-Thallium/Sestamibi stress test. The screening ability of this test has been summarized in 5 previous meta-analyses (9-13). The most recent assessed the quantitative aspect of the test (11) and showed that a negative test DID NOT reduce the likelihood ratio of an event; that is, a high proportion of the tests were false negatives. In fact, the perfusion defect had to measure greater than 30% of the LV mass before a positive test significantly changed the likelihood of a post-operative cardiac event. When thallium imaging and dobutamine stress echocardiography were compared, a negative stress echo was twice as effective as a negative thallium test in predicting the likelihood of a postoperative cardiac event. Overall, the balance of the clinical evidence supports the increased utilization of stress echo for preoperative screening. In addition, this test will supply resting ventricular function, wall motion abnormalities, and valve function. Finally, stress echo costs less, requires less infrastructure and is more convenient for patients.

Although the full potential of a resting 2D echocardiogram has not yet been exploited, it can be used in many ways to discriminate risk. However, the additional data from the echocardiogram appears to add significant information only in patients who clinically are at an increased risk of cardiac events (6-8). Rohde et al found that patients who were Class III or IV by the RCRI were 4 times more likely to suffer major post-operative cardiac complications if they had an abnormal transthoracic echocardiogram. The variables that were predictive included any degree of LV systolic dysfunction, moderate to severe LV hypertrophy, moderate to severe mitral regurgitation and an aortic gradient ≥20mm/Hg.

In summary, The ACC/AHA guidelines suggest that patients with active coronary disease need treatment and stabilization before having elective surgery. Furthermore, for those who have poor effort tolerance and RCRI risk factors, further stratification employing noninvasive tests is recommended.


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