CTA an Effective Gatekeeper in Invasive Angiography Candidates With Suspected CAD

Patients with suspected CAD whose risk level makes them clear candidates for invasive coronary angiography (ICA) can be safely and effectively treated using a selective referral strategy that employs CT angiography (CTA) as a gatekeeper, according to results from the randomized CONSERVE trial.

Moreover, the CTA-based approach reduces diagnostic costs by more than half, say researchers.

Senior investigator James K. Min, MD (NewYork-Presbyterian Hospital and Weill Cornell Medicine, New York, NY), said that CONSERVE is unique in that it focuses on patients who were already being referred for ICA based on an American College of Cardiology/American Heart Association guideline indication.

Making sure the right patients reach the cath lab is a key clinical concern, he told TCTMD. According to findings from the National Cardiovascular Data Registry, “two-thirds of patients who end up in the cath lab don’t have any actionable coronary disease for revascularization,” Min noted. “So, it seems to me we need a better way. If we can identify people with a noninvasive test that’s very low-dose and pretty cheap, that might be a better [approach].”

It’s far from the first study to show the potential of CTA in this role. Mere months ago at the 2018 European Society of Cardiology Congress, SCOT-HEART drew headlines with data demonstrating that adding CTA to the workup of patients with stable chest pain offered better 5-year outcomes compared with standard care. Some experts, though, were skeptical that the strategy could actually reduce the risk of coronary heart disease, death, or nonfatal MI by as much as 41%. The findings also came on the backdrop of the 2015 PROMISE trial, which failed to show an advantage of CTA as a gatekeeper in suspected CAD.

Results of the new study, led by Hyuk-Jae Chang, MD, PhD (Severance Cardiovascular Hospital, Yonsei University Health System, Seoul, South Korea), were published online December 12, 2018, ahead of print in JACC: Cardiovascular Imaging.

Selective vs Direct Referral

CONSERVE enrolled patients at 22 sites in North America, Europe, and Asia, randomizing 823 to selective referral and 808 to direct referral between December 2012 and July 2015. Ultimately, 784 patients underwent CTA in the selective referral arm and 719 underwent ICA in the direct referral arm. Mean age was 60 years, and 46.2% were women.

The median effective dose of radiation for diagnostic ICA is around 7 to 9 mSv, the researchers note. Here, the median effective dose with CTA was 6.5 mSV.

By 1 year, patients in both arms had the same MACE rate (death, MI, unstable angina, stroke, urgent and/or emergent coronary revascularization, or cardiac hospitalization), meeting noninferiority criteria. Both groups were equally likely to report being angina free. Follow-up ICA was less common with selective referral, as was the use of PCI. On the other hand, the use of downstream exercise ECG, nuclear stress testing, or stress echocardiography was greater in the selective-referral group.

Outcomes Based on Diagnostic Strategy

* not reported

Among patients who underwent ICA, whether as the index test or after crossing over from CTA, no obstructive CAD was found in 25% of the selective-referral arm versus 61% in the direct-referral arm (P < 0.001). Only 52% of the patients found to have obstructive CAD on CTA proceeded to have ICA.

Despite the greater use of follow-up testing in the selective-referral group, the cumulative cost of diagnostic tests was 57% lower among these patients. This “was solely due to the higher upfront costs associated with ICA,” the investigators write.

Speaking with TCTMD, Min seemed to have few reservations about the CTA-first strategy. One issue is the potential for double testing, when patients need to have ICA after undergoing CTA. “But I think the majority of people . . . will just get the single test and be treated with medical therapy and lifestyle modification. It’s a safer way to do it, I think, because you can [in many cases] avoid the need for invasive procedures,” he commented.

One take-home message is that, at least at the gatekeeper stage, CTA is enough, Min added. “There’s a lot of fancy tests out there that [involve] more cost and more effort and more time. What this study I hope definitively showed is that you don’t need any other tests—you just need the CT scan.”

David E. Newby, DM, PhD (University of Edinburgh, Scotland), who served as principal investigator of SCOT-HEART, points out in an editorial that CONSERVE is not without limitation. As an open-label study, for example, randomized patients “with more severe symptoms might have had a preference for invasive angiography and preferred to accept it, whereas those with mild symptoms might have a preference for less invasive investigations.” In all, 71 patients withdrew when assigned to ICA and 26 when assigned to CTA.

Still, he concludes, “the CONSERVE trial addressed an important clinical question and lends further weight to the increasing use of coronary CTA as a first-line test of choice in patients being investigated for coronary heart disease. . . . So now, the question is: why would you go straight for invasive coronary angiography? Should you not CONSERVE your energy and resources and use coronary CTA instead?”