American College of Cardiology

EAGLE ET AL., PERIOPERATIVE CARDIOVASCULAR EVALUATION FOR NONCARDIAC SURGERY UPDATE
http://www.acc.org/clinical/guidelines/perio/update/periupdate_index.htm

ACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery

A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery)

This is a Guideline Update of the 1996 Perioperative Guidelines. To highlight the changes, deleted text is indicated by strikeout, and revised text is presented in red. A clean version of the document, with changes fully incorporated, is available for download and print.

VI. Implications of Risk Assessment Strategies for Costs

The decision to recommend further noninvasive or invasive testing for the individual patient being considered for noncardiac surgery ultimately becomes a balancing act between the estimated probabilities of effectiveness vs. risk. The proposed benefit, of course, is the possibility of identifying advanced but relatively unsuspected CAD that might result in significant cardiac morbidity or mortality either perioperatively or in the long term. In the process of further screening and treatment, the risks from the tests and treatments themselves may offset or even exceed the potential benefit of evaluation. Furthermore, the cost of screening and treatment strategies must be considered. Although physicians should be concerned with improving the clinical outcome of their patients, cost is an appropriate consideration when different evaluation and treatment strategies are available that cannot be distinguished from one another in terms of clinical outcome.

The medical literature is helpful in defining the risk versus effectiveness in patients being considered for surgery. As noted above, patients who have had coronary revascularization within the previous 5 years and no recurrent ischemic symptoms are at such low risk for perioperative complications that further screening is unnecessary. Furthermore, absence of certain clinical markers defines a low-risk group that is unlikely to require further screening. This fact is true of patients who have an absence of prior angina, MI, HF, pathological Q waves on ECG, or diabetes mellitus, particularly with excellent or normal functional capacity (Table 1, Fig 1). In the remaining patients who have some increased markers of coronary artery risk, particularly when coupled with poor or unknown functional capacity, the issue of screening is especially relevant and difficult. Depending on referral patterns, the percentage of patients being considered for noncardiac surgery who fit this particular clinical category can vary greatly.

Cambria et al (165) have reported their experience using a selected clinical algorithm as discussed above. The cost assessment of this strategy in 201 consecutive patients is being considered for aortic surgery is presented in Fig.2. In this series, only 58 (29%) of patients considered for aortic repair underwent further noninvasive testing with exercise and/or dipyridamole thallium study. Sixteen patients (8%) were referred for cardiac catheterization, with preoperative coronary revascularization performed in 13 (6.5%). This selected use of noninvasive testing and very selected use of revascularization resulted in an overall perioperative cardiac mortality of just 0.5%.

To illustrate the cost implications of noninvasive testing and its potential cost-effectiveness, information from the Medicare databases was applied to the series by Cambria et al in Fig 2. If a cost of $567 per nuclear stress test is assumed, the accumulated costs of the selective screening of 58 patients is $32,886. In contrast the cost of screening all 201 patients would have been $113,967, a net increase of $81 081 over selective screening. Based on an annual incidence of 500,00 major vascular surgical procedures in the United States, selective testing could result in savings of more than $200 million, compared with a policy of routine testing. If the accumulated costs of the tests and coronary interventions are taken into account, the overall cost of using this particular selected screening strategy in the 201 patients was approximately $590,206 or $2,936 per patient.

As described previously, there are no randomized trials demonstrating the efficacy of screening and coronary interventions versus vascular surgery only. However, the low mortality reported by Cambria et al and others in patients who had undergone coronary revascularization suggests that such strategies improve survival. Using the Cambria data set as an example and assuming only one life was saved as a result of this strategy, the strategy would be at the expensive end of medical cost-effectiveness. If long-term benefits are considered and this patient lived 10 years, this strategy would have cost $59,020 per year of life saved (ignoring other subsequent costs). If the screening strategy was more successful, perhaps resulting in two lives saved, the cost per year of life saved would have been $29,510, a figure that is much more consistent with other currently accepted medical therapies. Importantly, many of these costs would likely be incurred at some point regardless of consideration for vascular surgery. In addition, Rihal et al (166) demonstrated a long-term survival benefit of coronary artery bypass grafting in patients with the combination of peripheral vascular disease and triple-vessel CAD. Therefore, by including both short- and long-term benefits, such a strategy might prove to be cost-effective.

Formal decision and cost-effectiveness analyses of this particular question have been done and have yielded highly varied results ^{(134,167-169)}. Because the exact amount of risk reduction from coronary revascularization in the clinical populations differs so much from center to center, it is difficult to determine the exact risks of aggressive screening and treatments vs. the benefits in terms of risk reduction. Additionally, the models all demonstrate that optimal strategy depends on the mortality rates for both cardiac procedures and noncardiac surgeries in the clinically relevant range. One recent model, which did not support a strategy incorporating coronary angiography and revascularization, used lower mortality rates than those used or reported in the other studies ^(91,168,169). Therefore, use of any decision and cost-effectiveness model in a specific situation depends on the comparability of local mortality rates to those of the model.

Figure 2 is meant to illustrate the potential costs versus effectiveness of such screening strategy. It is vitally important for the clinician to consider the cost implications of screening strategies, particularly in a field in which there are no randomized clinical trials evaluating the impact of therapies on outcomes.

One report suggested that the cost of a selected coronary screening approach, as described in these guidelines, was as low as $214 per patient ⁽²⁴⁵⁾. Several recent publications have shown a cost per year of life saved for this selected screening strategy of less than $45,000 when applied to patients undergoing vascular surgery ^(244,246). However, none of these studies included a strategy of selected screening followed by aggressive beta-blocker treatment in high-risk individuals, as recently described by Poldermans and colleagues ⁽²⁵²⁾. It is likely that this approach will be preferred over more aggressive coronary assessment/treatment strategies except perhaps among very high-risk subsets of patients ⁽²⁹³⁾. Prophylactic beta blockade represents an excellent strategy in patients for whom coronary revascularization for long-term benefit is not a serious consideration.