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Coronary CTA useful in patients with suspected angina due to CHD
Coronary CT angiography was associated with more appropriate use of invasive angiography and more use of preventive therapies in patients with suspected angina due to CHD, according to new data from the SCOT-HEART study.
In the main findings of SCOT-HEART, presented at the 2015 American College of Cardiology Scientific Session, coronary CTA more frequently led to a reclassification of CHD diagnosis and angina diagnosis compared with standard care, and it was associated with a trend toward lower MI.
In the present analysis, Michelle C. Williams, MD, and colleagues assessed changes in invasive coronary angiography, preventive treatments and clinical outcomes in the cohort of 4,146 patients with suspected angina due to CAD assigned coronary CTA plus standard care or standard care alone.
More preventive therapies
The rates of invasive angiography between the groups were similar (P = .451), but it was less likely to show normal arteries (20 vs. 56; HR = 0.39; 95% CI, 0.23-0.68) and more likely to show obstructive CAD (283 vs. 230; HR = 1.29; 95% CI, 1.08-1.55) in the coronary CTA group than in the standard-care group, according to the researchers.
Williams, from the British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Scotland, and colleagues also found that clinicians initiated more preventive therapies in the coronary CTA group than in the standard-care group (283 vs. 74; HR = 4.03; 95% CI, 3.12-5.2), with initiation occurring a median of 48 to 52 days after presentation.
From 50 days until the end of follow-up, reflecting the period in which preventive therapies were initiated, the incidence of MI was half as much in the coronary CTA group as in the standard-care group (17 vs. 34; HR = 0.5; 95% CI, 0.28-0.88), Williams and colleagues found.
The researchers determined that cumulative 6-month costs were higher in the coronary CTA group (difference, $462; 95% CI, 303-621).
High-quality evidence
In a related editorial, James K. Min, MD, and colleagues wrote that the analysis “is the highest-quality evidence to date for the comparative benefit of [coronary CTA] over standard-of-care approaches. ... Not only may [coronary CTA] be considered a reasonable alternative to stress testing for initial diagnostic CAD evaluation, but it may actually be preferred.”
James K. Min
Min, director of the Dalio Institute of Cardiovascular Imaging at NewYork-Presbyterian Hospital and Weill Cornell Medical College, and colleagues concluded that “the exact reason as to why improvements in event-free survival are observed amongst those undergoing [coronary CTA] is unknown and likely complex, but perhaps relate to the other findings noted by the SCOT-HEART and PROMISE investigators related to diagnostic accuracy, risk stratification, prediction of therapeutic benefit or simply a better understanding of a patient’s specific atherosclerotic disease process.” – by Erik Swain
Disclosure: Williams reports no relevant financial disclosures. Please see the full study for a list of the other researchers’ relevant financial disclosures. Min reports consulting for GE Healthcare and HeartFlow, serving on an advisory board for Arineta, holding equity in Autoplaq and MDDX and having a research agreement with GE Healthcare. The other editorial authors report no relevant financial disclosures.
Perspective
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These results show us that coronary CTA is an excellent first option for patients with chest pain, particularly if they don’t have known coronary disease. In my practice, particularly for the patients that are at relatively low likelihood of having coronary disease, the coronary CT is a preferred test because of what it shows that you don’t see with functional tests. You get to see the presence of nonobstructive CAD.
From this secondary analysis, it appears that by using coronary CTA, physicians responded to the testing and imaging available, and as a result had better medical management of their patients, with more preventative therapies that the standard-care group. That’s where the trial shows us how useful coronary CT can be in working up patients with chest pain.
It’s a challenge to determine why there was a difference in downstream outcomes here but not in PROMISE, a larger study whose primary outcome was clinical events, whereas SCOT-HEART’s had more to do with making the diagnosis of CAD. It’s important to note that the absolute number of patients between the two groups in SCOT-HEART is quite small. In this secondary analysis, 17 patients in the CTA group had MI after 50 days vs. 34 in the standard-care group. That’s a 50% relative risk reduction, but it’s a relatively small number of events. It’s not clear if this reduction would be repeatable if the study were conducted again.
The results won’t change my practice, because I already use a fair amount of coronary CTA. The bigger struggle is whether clinicians have access to quality coronary CTA. That is still the primary limiting factor: Do physicians work at a facility with the adequate equipment and the adequate expertise to perform these tests, and are they doing them in patients for whom the test will be paid by a third-party payer? The evidence is strong, but the realities of health care delivery will continue to limit CTA use.