For the process of preoperative evaluation to be a clinically useful exercise, two goals must be accomplished. First, the evaluation must result in the identification of a subgroup of patients who are at heightened risk of short- or long-term cardiac complications during or after surgery. Second, and equally important, once this higher-risk group is identified, there must exist some intervention that can modify that risk, whether canceling the surgery or intervening to make the surgery safer, such as by prescribing a medication, changing the operative approach or route of anesthesia, or correcting an underlying problem (e.g., through coronary revascularization). Several models have been devised that allow prediction of operative risk based on a patient's clinical history and the results of noninvasive testing. In culling findings from a wealth of studies, the ACC/ AHA consensus guidelines for preoperative evaluation before noncardiac surgery have become a widely used clinical tool, not only to identify operative risk but to serve as a guideline for the appropriateness of further testing and intervention.7 A complete review of preoperative risk stratification is beyond the scope of this chapter, but the key principles, as specifically related to indications for performing coronary angi-ography and revascularization before planned non-cardiac surgery, will be summarized.
The ACC/AHA guidelines recommend a stepwise approach to determining the need for invasive testing before noncardiac surgery. First, patient-specific risk is determined through assessment of clinical risk factors and symptoms, overall functional capacity, and the timing and results of prior coronary evaluation and treatment, if applicable. Second, surgery-specific cardiac risk is determined based on the expected incidence of cardiac events associated with the particular surgery that the patient is scheduled to undergo, as previously discussed. The decision whether to perform noninvasive stress testing is then based on assessment of these patient-specific and surgery-specific risks (Table 7-2; see Table 7-1). For example, a low-risk patient undergoing a low-risk surgery typically does not require further testing, because the results would be unlikely to alter surgical risk or outcome. Likewise, for high-risk individuals, such as patients with unstable angina or recent MI,
Table 7-2. Clinical Predictors of Increased Perioperative Cardiovascular Risk*
Rights were not granted to include this table in electronic media. Please refer to the printed publication.
From Eagle KA, Berger PB, Calkins H, et al: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery: Executive summary. A report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines. Circulation 2002;105:1257-1267.
who are scheduled to undergo a high-risk procedure, proceeding directly to coronary angiography is probably the most cost-effective and clinically useful strategy. As a general principle, noninvasive testing tends to be most cost-effective and clinically helpful in determining the need for subsequent angiography among patients with intermediate risk features.8 One group of investigators, for example, examined both the costs of preoperative cardiac testing and surgical outcomes before and after implementation of the AHA/ACC guidelines at their center; they determined that more selective referral for noninvasive testing, as advocated by the guidelines, was associated with reduced costs without sacrificing the low rate of cardiac events at their institution.9
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