Cardiac stress testing prior to abdominal aortic surgery: Widely variable utilization,costly,and of unclear benefit

Commentary on: Ponukumati AS, Columbo JA, Suckow BD, et al. The financial implications of cardiac stress testing prior to abdominal aortic aneurysm repair. Vasc Med 2022;27:470–476.

Cardiovascular complications, such as dysrhythmias, myocardial infarction, or heart failure, are the leading cause of morbidity and mortality in adult patients undergoing major vascular surgery.^1,2 This is likely related to the burden of systemic atherosclerosis and coronary artery disease among patients undergoing these procedures. To reduce perioperative cardiovascular complications, patients often undergo preoperative cardiac assessment, including a cardiac stress test, which has become an integral component of the modern medical preoperative risk stratification paradigm. At present, the multisocietal American College of Cardiology/American Heart Association guidelines propose an algorithm for preoperative evaluation and recommend stress testing for patients with cardiac risk factors, multiple comorbidities, and/or limited functional status if the results of such testing are thought to potentially change management. ³ Though these recommendations appear applicable to the health risk profile of most patients undergoing elective vascular surgery, they are based on low-quality evidence, and the subpopulation that derives the greatest benefit from preoperative stress testing remains poorly defined. As such, multiple manuscripts have demonstrated variation in cardiology consultation and cardiac stress testing prior to major vascular surgery.^4–6

In this issue of Vascular Medicine, Ponukumati and colleagues investigated the variation of cardiac stress testing prior to elective abdominal aortic aneurysm (AAA) surgery as well as the financial implications and the impact of stress testing on major adverse cardiovascular events postoperatively. ⁷ Analyzing 32,459 patients across 283 Vascular Quality Initiative (VQI) centers, the authors report that utilization of cardiac stress testing prior to elective endovascular aortic aneurysm repair (EVAR) and open AAA repair varied substantially. Indeed, the median rate of stress testing for EVAR was 36.8% across centers and ranged from 13% to 68.6%. Additionally, stress testing prior to open AAA repair varied from 15.9% at the lowest centers to 76.5% at the highest centers. Given this marked variation in stress testing, the authors calculated financial implications using locally applied charges. ⁷ The cost of stress testing increased substantially over the hospital quintiles when divided based on rate of cardiac stress testing for both EVAR and open AAA repair. For EVAR, the amount charged per 1000 patients ranged from $125,806 for the lowest quintile centers to $665,975 at centers in the highest quintile. In a similar fashion, the estimated amount charged for stress testing prior to open AAA repair was $153,861 per 1000 patients for centers in the lowest quintile and increased to $825,473 accordingly among centers in the highest quintile. Lastly, and perhaps most importantly, the authors demonstrate that for both EVAR and open AAA repair there was no significant difference in center-specific major adverse cardiovascular events (MACE) postoperatively when stratified by how often these centers obtained preoperative cardiac stress testing, although those patients with a positive stress test did have significantly higher MACE. ⁷ This finding calls into question the overall value of preoperative cardiac stress testing if centers that perform a substantially higher number of stress tests and incur increased healthcare cost do not observe a reduction in postoperative cardiovascular complications.

The use of the preoperative stress test has become a staple in contemporary surgical practice. In the hope of accurately risk stratifying patients noninvasively (and perhaps reducing medicolegal exposure), stress testing will often be obtained by vascular surgeons before elective vascular surgery, even in the absence of formal cardiology consultation. Evidence of ischemia on cardiac stress testing has been associated with increased rates of perioperative myocardial infarction, hospitalization, and postoperative mortality. ⁸ However, the rationale for stress test usage in clinical practice is highly variable and ultimately determined by the treating physician, anesthesiologist, or operative surgeon. The results of the current study agree with prior studies that demonstrated stress testing patterns across the VQI centers in North America do not appear to have a clear evidence-based rationale and, rather, defaulted to local or individual practice patterns. ⁹ The rationale for this variance in practice patterns remains elusive. Some could hypothesize that cardiac stress testing varies by center as some centers might treat ‘higher-risk’ patients compared with other centers. However, this is unlikely as these authors have previously demonstrated that cardiac risk scores for the patients treated at centers in the highest quintile of stress test use and those in the lowest quintile were remarkably similar. ⁹

The question, therefore, remains: who should undergo preoperative stress testing? It is difficult to determine for which patients a preoperative stress test will be unnecessary and for which patients it will be valuable. In Ponukumati et al.’s study, ⁷ like many other studies, we do not know which patients in whom a positive test was obtained also had adjustments of their medications or other interventions, such as coronary revascularization, prior to AAA repair. Moreover, we do not know what the pretest probability of ischemia was in these patients. However, the degree of widespread variation in stress testing reported by Ponukumati and colleagues was almost certainly indicative of the use of unnecessary testing at some centers, with the associated financial implications for such testing. ⁷ Prior investigations on the value of various preoperative testing strategies have often centered around low-risk surgery, like cataract surgery, demonstrating an absence of a morbidity and mortality benefit while incurring a marked cost to the healthcare system. ¹⁰ Although elective EVAR and open AAA repair are higher-risk surgeries than cataract surgery, the current study suggests that there are areas for value analysis surrounding preoperative stress tests prior to aortic surgery to limit costs but still providing high-quality vascular surgical care. Further studies to better delineate which patients should undergo preoperative stress testing to maximize benefit and minimize financial implications are indicated. Until better prospective studies exist, we recommend ordering a stress test in those patients with a strong clinical history of coronary heart disease, such as prior revascularization (unless recently revascularized), those with active ischemic symptoms, and in those with positive biomarkers such as troponin and NT-proBNP. ¹¹

Additionally, to aid in the sorting of preoperative AAA patients that would derive the most benefit from a cardiac stress test, the VQI Cardiac Risk Index ¹² can be employed in a procedure-specific fashion (EVAR vs open AAA repair) as a valid clinical decision-making tool to predict postoperative MACE and as such stratify patients for potential cardiac stress testing. This is helpful for patients who live a sedentary lifestyle and as such do not experience exertional angina symptoms, but whose medical comorbidities place them at elevated risk of cardiac complication.

In conclusion, although the most appropriate rate of stress testing remains an empirical question, the high level of variation may warrant a more uniform approach toward preoperative stress testing for aortic surgeries across centers with the potential to streamline care and reduce costs.