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CRESCENT-II: Tiered cardiac CT protocol more efficient, faster than functional testing
A tiered cardiac CT protocol with dynamic perfusion imaging had similar effectiveness to functional testing in patients with suspected CAD, but took less time to process and resulted in fewer inappropriate invasive procedures, according to the CRESCENT-II trial.
Previous research has shown CT angiography can rule out CAD, but it was not known whether incorporating CT myocardial perfusion imaging as part of a tiered diagnostic approach would improve the clinical value and efficiency of cardiac CT in patients with angina, the researchers wrote in the study background.
Marisa Lubbers, MD, from the departments of cardiology and radiology at Erasmus Medical Center, Rotterdam, the Netherlands, and colleagues randomly assigned 268 patients (mean age, 58 years; 49% women) with stable angina (mean pretest probability, 54%) and suspected obstructive CAD (probability, 10% or greater) to cardiac CT or guideline-directed functional testing. Ninety-five percent of the functional testing group received an exercise ECG.
Those assigned cardiac CT underwent a calcium scan followed by CT angiography if calcium was present. Those with 50% stenosis or greater on CT angiography underwent CT myocardial perfusion imaging.
The primary endpoint was rate of invasive coronary angiograms without a European Society of Cardiology class I indication for revascularization.
Downstream tests, procedures
At 6 months, the primary outcome was lower in the CT group compared with the functional-testing group (1.5% vs. 7.2%; P = .035), Lubbers and colleagues wrote.
There was a higher proportion of invasive angiograms with a revascularization indication in the CT group vs. the functional-testing group (88% vs. 50%; P = .017), according to the researchers.
Median duration until final diagnosis was shorter in the CT group (P < .001).
Further testing was required in 13% of patients assigned CT and 37% of patients assigned functional testing (P < .001), according to the researchers.
At a mean follow-up of 250 days, major adverse CV events occurred in 3% of both groups (HR = 1.07; 95% CI, 0.27-4.26), the researchers wrote.
None of the 45 patients in the CT group ruled out based on a calcium score of 0 had adverse events.
Median cumulative radiation dose was higher in the CT group (3.1 mSv vs. 0 mSv; P < .001), Lubbers and colleagues wrote.
“In patients with stable angina and a typically low CAD prevalence, the challenge is to accurately rule out CAD in the majority by relatively simple means, while comprehensively assessing those who may benefit from revascularization,” the researchers wrote. “A tiered, comprehensive cardiac CT protocol, including dynamic perfusion imaging, appears to be a fast and efficient alternative to standard functional testing in these patients.”
Improving patient outcomes
In a related editorial, Leslee J. Shaw, PhD, FACC, FASNC, FAHA, professor of medicine in the division of cardiology at Emory University, co-director of Emory Clinical Cardiovascular Research Institute and a member of the Cardiology Today Editorial Board, and colleagues wrote that the results “revealed a greater need for downstream or induced testing following functional testing; a rate much greater than that of CT.”
What is needed, they wrote, is “greater insight into the optimal trial design that fits the risk of an imaging cohort while incorporating aspects of imaging risk markers and their unique contributions to driving optimal clinical management. It is this directed link between an imaging procedure and targeted clinical care that provides the necessary components for improving patient outcomes.” – by Erik Swain
Disclosures: Lubbers and the editorial authors report no relevant financial disclosures. Please see the study for a list of the other authors’ relevant financial disclosures.
Perspective
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Although the primary outcome — cardiac CT results in fewer normal angiograms than patients evaluated with functional testing — has been demonstrated in previous trials, the tiered CT approach is interesting and exemplifies individualized patient care compared to uniformly performing the same protocol on all patients. It is also interesting that more than one-third of patients in the functional testing group had inclusive results with the initial diagnostic test.
Although there are advantages of the tiered cardiac CT protocol, the implementation in a high-volume medical center would be very challenging. Needing physician input after each tier is expertise-intensive and can be burdensome in a high-throughput environment. The authors did not include the length of CT exam, but that would have been interesting to know.
CT myocardial perfusion imaging adds a functional evaluation of ischemia to the anatomic assessment by cardiac CTA, however it comes at the cost of high radiation exposure. Whereas CT-derived fractional flow reserve, another means of assessing the functional significance of stenosis identified by cardiac CTA, does not expose patients to any additional radiation or medications because it is derived from the cardiac CTA images. A head-to-head comparison of CT myocardial perfusion imaging vs. FFRCT used in a tiered protocol would be very insightful.