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Tiered imaging protocol viable alternative to functional testing
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A comprehensive, tiered cardiac CT protocol that incorporates CT myocardial perfusion imaging with CT angiography may provide a safe and efficient diagnostic alternative to functional testing for patients with possible CAD, according to a study published in JACC: Cardiovascular Imaging.
“In this multicenter randomized clinical trial, a comprehensive cardiac CT examination that involved a stepwise performance of a calcium scan, CTA and [CT myocardial perfusion imaging] was compared with the current standard of functional testing for suspected CAD,” Marisa Lubbers, MD, of the departments of cardiology and radiology at Erasmus University Medical Center, Rotterdam, the Netherlands, and colleagues wrote. “The main findings are that a tiered cardiac CT protocol improves the efficiency of invasive angiography without increasing overall catheterization rates. The combined CT protocol achieved a diagnosis faster, and it removed the need for additional noninvasive testing.”
For the CRESCENT-II trial, researchers randomly assigned 268 patients aged 18 years or older (mean age, 58 years; 49% women) who had symptoms suggestive of CAD to the CT group (n = 130) or the functional testing group (n = 138) between July 2013 and November 2015.
Tiered protocol
The tiered CT approach consisted of a calcium scan and, if calcium was detected or if patients had a greater than 80% pretest probability of CAD, a subsequent CT angiography was performed. After the CT angiography was assessed, all patients with at least 50% stenosis underwent adenosine-stress dynamic CT myocardial perfusion imaging.
The functional testing strategy was based on international guidelines, which commonly included a symptom-limited exercise electrocardiography.
The primary outcome was the negative invasive angiography rate, which researchers defined as the number of angiograms without a European Society of Cardiology class I indication for revascularization.
Invasive procedures lower
At 6 months, researchers found that the rate of invasive coronary angiograms was 1.5% in the CT group and 7.2% in the functional testing group (P = .035) and that the proportion of invasive angiograms with a revascularization indication was 88% in the CT group and 50% in the functional testing group (P = .017).
As for diagnostic efficiency, the majority of patients in both groups were given a final clinical diagnosis the same day, with this occurring more frequently in the cardiac CT group than the functional testing group (87% vs. 64%; P <.001).
In addition, 13% of patients in the CT group and 37% of patients in the functional testing group required further testing (P < .001).
Researchers determined that, although the median cumulative radiation dose was lower for the functional testing group than for the CT group (0 mSv vs. 3.1 mSv; P < .001), the adverse event rate in both groups was 3%.
“In patients with stable angina and a typically low CAD prevalence, the challenge is to rule out CAD accurately in the majority by relatively simple means while comprehensively assessing those patients 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.” – by Melissa J. Webb
Disclosures: Lubbers reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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