To the Editor:--As clinicians who run a preoperative evaluation center and provide intraoperative anesthesia and postoperative intensive care, we, like Mangano, have been frustrated with the problem of preoperative cardiac risk assessment. However, as we question whether "a cardiac risk assessment paradigm is possible," our answer is slightly different. Whereas Mangano concludes with a call for development of screening algorithms and large-scale trials assessing testing technologies, we suggest that a more sensitive, specific, and cost-effective paradigm is probably not feasible and, equally important, may not be necessary. Rather, we believe that the focus should be shifted from preoperative testing to development of improved methodologies for postoperative ischemia detection and treatment.
For the past two decades, the conventional approach to cardiac risk management in anesthesia has been preoperative screening (to detect high-risk patients) and special intraoperative monitoring and interventions (to avert or immediately correct evolving ischemia). A variety of screening tests have been proposed to identify high-risk patients who are either asymptomatic or have stable symptomatology; however, these tests have a low positive predictive value and a real incidence of false negatives. The positive predictive value of these tests is low, not because the tests are unable to detect significant coronary disease, but rather, because current management strategies have reduced the likelihood of patients with coronary disease experiencing major cardiac complications. Moreover, because plaque rupture can occur in physiologically insignificant lesions, there always will be a low but real incidence of false negatives.
The current economic environment is challenging all of us to examine our practice patterns and evaluate whether they are cost-effective. We believe that the way preoperative cardiac screening tests are used does not meet the challenge of cost-effectiveness. Available tests are expensive, and detection of unrecognized coronary stenosis, by necessity, entails fairly widespread testing. Data on the societal costs of preoperative cardiac testing are difficult to obtain, but a recent survey indicates widespread preoperative testing in vascular surgery patients (60% of 400,000 cases/year). According to current estimates, 9 million patients are at risk for cardiac complications each year ; whereas the actual number undergoing preoperative testing is unknown, the cost of cardiac screening is enormous. Cost-effective testing also requires that the results can be used to change outcome. Available data do not support that this is the case for preoperative cardiac screening tests. When angiography and angioplasty or bypass surgery are performed for the sole purpose of reducing perioperative risk, overall morbidity and mortality is not reduced and may be increased. .
The perioperative period can be viewed as a stress test, subjecting the body to neuroendocrine, hemodynamic, thermal, and coagulation changes. These stresses are thought to account for most perioperative myocardial infarctions. The preponderance of available data indicates that the postoperative period has the highest incidence of cardiac events. [4,5]Yet, we have invested relatively little effort and resources in postoperative research and management strategies. Therefore, we believe that the potential for novel discoveries and cost-effective therapies may be comparatively greater. One possible approach would use continuous 12-lead electrocardiographic monitoring in at-risk patients during the first 48 h after surgery. Systems are available with central alarm capabilities that can be used on a general surgical floor. Based on recent data showing that ischemia precedes postoperative cardiac events in most patients [4-6]and that there is an apparent threshold of 120 min of postoperative ischemia before development of major morbid events, [5,6]prompt ischemia detection should allow for timely intervention and a reduced incidence of postoperative infarction. Because postoperative ischemia also predicts long-term cardiac morbidity and mortality, [7,8]improved methods for ischemia detection could use the physiologic stress of the perioperative period as a "surgical stress test."
In summary, if we wish to reduce perioperative cardiac complications, we need to develop a comprehensive approach that deploys our resources throughout the perioperative period most effectively. We contend that systematic study and consideration to the relatively unexplored avenues of postoperative management should be made before we make additional and massive investments in approaches that have been in place for decades.
Brian A. Rosenfeld, M.D., F.C.C.M., Associate Professor, Anesthesiology, Medicine and Surgery.
Michael J. Breslow, M.D., F.C.C.M., Associate Professor, Anesthesiology, Medicine and Surgery.
Todd Dorman, M.D., Assistant Professor, Anesthesiology and Surgery, Adult Critical Care Division, Anesthesiology and Critical Care Medicine, Johns Hopkins, 600 North Wolfe Street, Meyer 299A, Baltimore, Maryland 21287-7294.