The use of CT angiography (CTA) to help guide preventive surgical strategies for patients undergoing redo CABG appears to be justified, based on results published in the September issue of Circulation: Cardiovascular Quality and Outcomes. The model showed that the cost of preventive strategies had a greater influence over cost-effectiveness than did the cost of CTA.
Surgeons may encounter procedural complications when performing reoperative CABG because the patient population has a high-risk profile (Ann Thorac Surg 2005;80:1719-1727). The use of thoracic multidetector CTA may help mitigate risk by identifying features that contribute to potentially adverse outcomes and higher costs. Based on CTA findings, surgeons may change their approach to avoid or minimize these complications.
From a clinical perspective, research supports the use of CTA in the setting of isolated CABG, suggested Hemal Gada, MD, MBA, of the cardiovascular medicine department at the Heart and Vascular Institute at the Cleveland Clinic, and colleagues. But from a provider’s perspective, whether the improved outcomes justify the cost of imaging remained in question.
“Because the cost of imaging appears likely to be bundled into an episode of care, we sought to perform a cost-effectiveness analysis of CTA in the setting of isolated reoperative CABG using a decision-analytic model,” they explained.
The Markov model compared the management of a hypothetical cohort of 10,000 patients grouped either to CTA imaging before reoperative CABG or to no imaging. The CTA group then was stratified as low risk or high risk, based on imaging results, with some but not all patients in both the low- and high-risk subgroups receiving preventive surgical strategies (PSS). Patients in the no-CTA group had no PSS. The model included data taken from literature on costs (in 2012 U.S. dollars), health states, high-risk features and outcomes. Analysts incorporated costs for PSS based on estimates from their experience at the Cleveland Clinic.
The use of CTA offered a lifetime quality-adjusted life year (QALY) gain of 0.04, or two weeks of life at full quality, which Gada et al described as “within the realm of what has been defined previously as a meaningful increment in survival.”
The lifetime cost of use of CTA was higher than the cost of not using CTA, $74,869 vs. $73,471, for an incremental cost-effectiveness ratio of $34,950/QALY. The authors pointed out that figure met the criteria for incremental cost-effectiveness.
Based on their sensitivity analyses, the cost of CTA in the range of $0 to $2,000 had no influence on the superiority of a strategy. Instead, the cost of PSS largely was the driver of CTA’s net monetary benefit.
“[I]mplementing PSS adds to the overall cost of reoperative CABG, and PSS should only be used when deemed necessary, a decision that is guided heavily, if not solely, by findings on CTA,” they wrote. “In the reference case, when PSS cost was less than $12,000, CTA use derived superior net monetary benefit. This finding is especially important given the small difference in QALYs (0.04) derived from CTA use versus no CTA use.”
Among limitations, the authors noted that the figure used to estimate PSS cost was based on their institution and may not be comparable in other institutions. Outcomes were derived from two retrospective studies that themselves may be limited by confounding, selection biases and unmeasured variables. Nor did the study examine the effect of more frequent PSS use.
“Given that the cost-effectiveness of CTA in the setting of reoperative CABG is driven by the cost of PSS, it would be useful to study whether more frequent PSS use, at the surgeon’s discretion, would be justified by the added costs associated with PSS,” they recommended.