Using Coronary CTA as Gatekeeper Test in Suspected Angina Linked to Better Outcomes: SCOT-HEART

In patients with suspected angina due to coronary heart disease, the greater diagnostic certainty achieved with coronary CT angiography (CTA) versus stress testing results in more appropriate use of invasive angiography, greater  use of preventive medications, and a lower MI risk, according to a post hoc analysis of the SCOT-HEART trial.

Although the improvement in outcomes was suggested by the previously published main results of the trial, this new analysis, reported by lead author Michelle Williams, MD (University of Edinburgh, Scotland), and colleagues, takes into account the delay between coronary CTA and prescription of new preventive therapies.

No prior trials of imaging modalities for diagnosing coronary heart disease have shown an impact on clinical outcomes, senior author David Newby, MD (University of Edinburgh), told TCTMD. “This is really the first one to say actually it improves your outcome if you follow it through,” he said.

Thus, the findings should encourage greater use of CTA, Newby said, noting that US guidelines favor stress imaging as the initial diagnostic approach, with CTA considered if patients cannot undergo such testing. “SCOT-HEART’s flipping that on its head. You should really be doing a CT as your first-line choice,” he said, adding that “as scanners get more sophisticated and the radiation doses come down even further . . . this is a technique that will be used widely.”

The main SCOT-HEART results, presented at the American College of Cardiology 2015 Scientific Sessions and simultaneously published in the Lancet, showed that—when added to standard care (stress testing according to established local protocols)—coronary CTA improved diagnostic certainty over standard care alone, leading to changes in subsequent management and a potential clinical benefit. Whether those changes in management were appropriate had remained unclear, providing the impetus for the current analysis, published online ahead of print in the April 19, 2016, issue of the Journal of the American College of Cardiology.

Better Use of Invasive Angiography, Preventive Medications

Coronary CTA, which was performed at a median of 12 days after randomization, resulted in a significantly higher number of cancellations of invasive angiograms (29 vs 1) and of new invasive angiograms (94 vs 8) by 6 weeks.

Overall, coronary CTA was not associated with a greater likelihood of undergoing invasive angiography, but exams ordered in patients who underwent coronary CTA were less likely to show normal coronary arteries and more likely to show obstructive CAD, suggesting more appropriate testing in that group.

“Given the potentially greater hazards and costs of invasive angiography, our findings indicate that [coronary CTA] is as an effective and readily applicable gatekeeper for the conduct of invasive coronary angiography with a view to coronary revascularization in patients with suspected angina pectoris due to coronary heart disease,” the authors write.

There was a nonsignificant trend toward more coronary revascularization procedures in the coronary CTA group (233 vs 201; P = .06).

As for medical therapy, patients who underwent coronary CTA were significantly more likely to have preventive therapies cancelled (77 vs 8) and newly initiated (293 vs 84), findings that remained consistent for each drug type examined: antiplatelet, statin, ACE inhibitor.

The improved use of angiography and preventive medications appeared to translate into better outcomes. The number of MIs that occurred in the first 49 days of follow-up did not differ between the trial arms, but a landmark analysis starting at 50 days (the median time to new preventive medication prescriptions) showed that half as many MIs occurred in the coronary CTA arm going forward (17 vs 34; HR 0.50; 95% CI 0.28-0.88).

Cumulative costs through 6 months were higher in the coronary CTA group ($1,900 vs $1,438; P < 0.001), driven by direct costs of the CT scan.

Should Guidelines Change?

PROMISE, which was first reported a day before SCOT-HEART, was a similar trial comparing initial evaluation of chest pain using coronary CTA instead of functional testing. Although PROMISE, like SCOT-HEART, demonstrated improved use of the cath lab and preventive medications, that did not translate into a lower rate of the composite primary outcome (death, MI, hospitalization for unstable angina, or major procedural complications).

Commenting on the current study for TCTMD, Pamela Douglas, MD (Duke University, Durham, NC), principal investigator of the PROMISE trial, said the discrepancy between the trials in terms of the impact of coronary CTA on clinical outcomes is unexplained.

Questions also remain about why performing coronary CTA, a diagnostic test, would have a beneficial effect on clinical outcomes, she said, pointing out that the issue is difficult to study because of how many decisions about patient management are made after the test is completed.

Although SCOT-HEART helps to illuminate those issues, it was not designed to provide the fine details about physician decision making that are needed to uncover exact mechanisms linking coronary CTA to improved outcomes, Douglas said. A new trial would be needed to get that type of information, she added.

Until then, however, there are enough data from PROMISE, SCOT-HEART, and other studies to boost coronary CTA in the guidelines, Douglas said. “I think there’s good evidence, particularly if you have access to functional information with your CT like an FFR or CT perfusion, that that’s at least as good as a stress imaging test,” she said.

In an accompanying editorial, James Min, MD (Weill Cornell Medical College, New York, NY), and colleagues also provide support for coronary CTA.

“This secondary analysis of SCOT-HEART is the highest-quality evidence to date for the comparative benefit of [coronary CTA] over standard-of-care approaches,” they write. The findings, combined with results from previous studies, “suggest that not only may [coronary CTA] be considered a reasonable alternative to stress testing for initial diagnostic CAD evaluation, but it may actually be preferred.”