‘CONSERVE’ Your Energy and Resources: Selective Referral Strategy Using CCTA Non-Inferior to Direct Referral Strategy to ICA for Suspected CAD CONSERVE Trial: A Randomized, Controlled, Open-Label Trial

The findings of a randomized, controlled, open-label trial conducted by Dr. Hyuk-Jae Chang, Division of Cardiology, Severance Cardiovascular Hospital, Seoul, South Korea and his colleagues, has reported that in stable patients with suspected coronary artery disease (CAD) who are eligible for invasive coronary angiography (ICA), the comparable 1-year major adverse cardiovascular events rates following a selective referral and direct referral strategy were suggestive that both diagnostic approaches were similarly effective. Moreover, in the selective referral strategy, the reduced use of ICA was associated with a greater diagnostic yield, which supported the usefulness of coronary computed tomographic angiography (CCTA) as an efficient and accurate method to guide decisions of ICA performance. The findings were published online in JACC: Cardiovascular Imaging.

Invasive coronary angiography (ICA) had been a commonly performed diagnostic test for the evaluation of stable symptomatic patients with suspected coronary artery disease (CAD) to guide decisions of coronary revascularization. Although current professional guidance documents offered direction for appropriate selection of patients for elective ICA, previous studies observed that most individuals who underwent nonemergent ICA did not have actionable CAD. For these patients, ICA was an invasive, expensive procedure that could be unnecessary. When CAD was identified, ICA was frequently associated with ad hoc percutaneous coronary intervention (PCI) at the time of ICA, but whether this approach improved clinical outcomes was not clear. It was also known that among patients presenting with signs and symptoms suggestive of coronary artery disease (CAD), a sizeable proportion referred to ICA did not have a significant, obstructive stenosis. In light of this, the study aimed to compare the safety and diagnostic yield of a selective referral strategy using coronary computed tomographic angiography (CCTA) compared with a direct referral strategy using invasive coronary angiography (ICA) as the index procedure. In this multinational, randomized clinical trial of patients referred to ICA for nonemergent indications, a selective referral strategy was compared with a direct referral strategy. The primary endpoint was noninferiority with a multiplicative margin of 1.33 of composite major adverse cardiovascular events (blindly adjudicated death, myocardial infarction, unstable angina, stroke, urgent and/or emergent coronary revascularization or cardiac hospitalization) at a median follow-up of 1-year.

The investigators found that at 22 sites, 823 subjects were randomized to a selective referral and 808 to a direct referral strategy. At 1 year, selective referral met the noninferiority margin of 1.33 (p ¼ 0.026) with a similar event rate between the randomized arms of the trial (4.6% vs. 4.6%; hazard ratio: 0.99; 95% confidence interval: 0.66 to 1.47). Following CCTA, only 23% of the selective referral arm went on to ICA, which was a rate lower than that of the direct referral strategy. Coronary revascularization occurred less often in the selective referral group compared with the direct referral to ICA (13% vs. 18%; p < 0.001). Rates of normal ICA were 24.6% in the selective referral arm compared with 61.1% in the direct referral arm of the trial (p < 0.001).

Thus, the investigators concluded that in this trial of stable patients with suspected CAD who were referred for guideline-directed ICA, a selective referral strategy was found to result in similar MACE rates at 1 year of follow-up compared with a direct referral strategy. Growing evidence supported that noninvasive anatomic testing by CCTA alone, as a gatekeeper procedure, could prove advantageous in promptly and accurately identifying candidates for downstream procedures. These data and similarly relevant findings from other randomized trials called for revisions to the current ischemic heart disease guidelines for the evaluation of patients with stable ischemic heart disease. Indeed, these results supported the use of CCTA as a front-line diagnostic procedure, followed by selective referral to ICA of a greater proportion of patients with obstructive CAD.

Author Dr. James K. Min, Department of Radiology and Medicine, Dalio Institute of Cardiovascular Imaging, Weill Cornell Medicine, New York, commented, “The CONSERVE trial aimed to evaluate, in a randomized trial setting, the potential to safely shift lower risk patients eligible for elective ICA to less expensive CCTA. Because of the high rate of ICA across the United States, the implications of findings from the CONSERVE trial could expedite a patient’s diagnosis of CAD while providing for a prompt and efficient diagnostic pathway guided by CCTA findings.” Highlighting his opinion on the matter, Prof. David E. Newby from the University of Edinburgh, Scotland, remarked, “The CONSERVE trial addressed an important clinical question and lends further weight to the increasing use of CCTA as a first-line test of choice in patients being investigated for coronary heart disease. It showed that even in those who are directly referred for invasive coronary angiography, CCTA is a non-inferior alternative that reduces the need for invasive angiography, decreases invasive procedures, and appears to result in similar short-term clinical outcomes. So now, the question is why would you go straight for invasive coronary angiography? Should you not CONSERVE your energy and resources, and use CCTA instead?”