The results of the highly anticipated CT-STAT trial were released this week in the Journal of the American College of Cardiology. The study objective was to compare the efficiency, cost, and safety of coronary CT angiography to rest-stress myocardial perfusion imaging to diagnose coronary artery disease (CAD) for emergent low-risk patients. Overall, CCTA was found to be more efficient and less costly than traditional SPECT imaging in the diagnostic work-up of this patient subset. While helping to further validate the role of CCTA to expedite care for appropriate chest pain patients, the study raises new questions about future opportunities for CCTA, and if it can supplant more established tests for diagnosing and ruling-out CAD.
Numerous clinical studies have been published over the past several years which have assessed the performance of coronary CT angiography – a non-invasive diagnostic imaging procedure used to identify obstructed coronary arteries suggestive of CAD. In particular, many of these studies have focused on the ability to effectively diagnose and rule-out CAD compared to more traditional and well-established tests, such as SPECT myocardial perfusion imaging and invasive coronary angiography. What has become clear over time is that CCTA is an effective test to confidently rule-out CAD when test results are negative, and to do so without significant concern for future major complications or adverse cardiac events. However, certain clinical indications must be satisfied for providers to have confidence in CCTA; as the pre-test probability or risk of CAD increases, the diagnostic value of CCTA falls, and these higher-risk patients are typically sent straight to the cath lab for an invasive coronary angiogram, and subsequently, an intervention.
Sizing the Opportunity
As reflected in recently updated appropriate use criteria and expert consensus statements, coronary CT angiography is best performed in the setting where patients are considered to be of low-risk for CAD. These patients without known CAD or conclusive presence of disease upon ECG testing, serial biomarkers, and other tests may not have significant stenoses in the coronary arteries requiring intervention. Traditionally, SPECT myocardial perfusion imaging (MPI) has been used in this pathway to provide greater sensitivity and specificity in the diagnostic evaluation of these patients. However, SPECT myocardial perfusion imaging is not a perfect exam, is lengthy, can expose patients to significant radiation, and is costly from an overall care management perspective. To that end, many experts believe, and an increasing body of evidence suggests, that coronary CT angiography can serve as a viable alternative to traditional SPECT myocardial perfusion imaging with respect to clinical efficacy, and can also be a more cost-effective procedure by expediting care. With an estimated 8 million patients seen in U.S. emergency departments with chest pain, and over $10 billion spent on evaluating these patients, the societal and economic burden of CAD – and potential opportunity for resource-saving techniques – is significant.
The CT-STAT Trial and Key Findings
In addition to numerous other previous studies, the “Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patient to Treatment” trial – or “CT-STAT” for short – was launched to test this hypothesis. CT-STAT differs from many others with respect to its size and structure, as a 16-center, randomized controlled trial powered to assess the efficiency of CCTA as a reliable alternative to SPECT imaging for low-risk emergent chest pain patients. The international trial enrolled patients from 11 academic medical centers and 5 community hospitals, with the majority of patients seen at U.S. facilities. In total, over 6,600 patients were screened, with nearly 750 ultimately enrolled in the trial after application of strict inclusion and exclusion criteria.
Overall, the 361 patients randomized to the CCTA group were evaluated more efficiently and with fewer expenses than the 338 patients in the rest-stress SPECT MPI group. Time-to-diagnosis was reduced by 54 percent in the CCTA group at a median of 2.9 hours, compared to 6.3 hours in the MPI group. Additionally, the costs of care were 38 percent lower in the CCTA group with a median expense of $2,137 compared to $3,458 in the MPI group. In both groups, no cardiovascular-related deaths were reported after 6 months follow-up, and the differences between cumulative clinical events at the index visit and at the 6 month mark were not statistically significant – patients in both groups underwent subsequent invasive coronary angiography, PCI, and CABG at nearly the same rates.
The CT-STAT trial sheds further light on the future opportunities for CCTA as both a clinically efficacious and potentially cost-effective solution in the management of a specific subset of chest pain patients. However, like the exam itself, the CT-STAT trial is not without its limitations. First, only a subset of patients actually benefit from CCTA, underscoring the importance of using evidence-based practice to ensure chest pain patients are receiving the most appropriate tests given their clinical characteristics and medical history upon presentation. As estimated by the study investigators, “approximately 58 percent of screened acute chest pain patients could be triaged with CCTA,” and it should not be considered a “one size fits all approach” for all ED patients. Additionally, the CT-STAT trial is not a true cost-effectiveness study in that it did not utilize direct cost measurements; instead, it relied upon using cost-to-charge ratios. Still, the results are important because they did consist of the total costs of care from the index test onward; costs for patients who went on to receive additional testing, an invasive coronary angiogram, were admitted, and/or received some form of intervention were included in both groups, providing a more complete depiction of the overall costs of care for these patients.
Assessing the Future for CCTA, Other Tests
An accompanying editorial commentary from Dr. Michael Salerno and colleagues from UVA Health System also calls to attention some important considerations regarding the future of CCTA, and specifically, some of the results from the CT-STAT trial. In general, ever-changing clinical practice patterns and the availability of new technology engineered for improved quality, speed, and lower radiation doses will require new studies like CT-STAT to more effectively determine the role of CCTA relative to other modalities and techniques. For example, prospective ECG-gating and high-pitch CT imaging techniques were not used in the CT-STAT trial, which have been demonstrated to significantly reduce radiation exposure during CCTA. Also, physicians are gaining greater confidence in using stress-only protocols for low-risk chest pain patients, and with newer SPECT cameras designed to minimize exposure and reduce exam time, the efficiency measures for rest-stress MPI in the CT-STAT trial may be fully reflective of today’s practice.
Accordingly, many more studies like CT-STAT are necessary to identify the most appropriate set of tests and imaging procedures for chest pain patients. The notion of risk-stratification is absolutely essential to ensure not only the right patients are receiving the right test at the right time, but also to ensure these procedures are making a demonstrable impact on clinical outcomes. At the Roundtable, we eagerly look forward to continued evidence evaluating the role of CCTA, nuclear imaging (SPECT and PET), MRI, echocardiography, and other more refined tests in the management of CAD. We’d love to hear your perspectives and learn more about what you are doing now and your plans for the future for these many cardiovascular imaging procedures!