Montreal, QC - In stress testing using regadenoson (Lexiscan, Astellas), detection rates of myocardial ischemia were similar with less invasive computed-tomography (CT) perfusion imaging compared with the reference method, single-photon-emission CT (SPECT) imaging, in a phase 2 trial.
Regadenoson, a selective adenosine-receptor agonist that produces coronary vasodilation in patients unable to undergo exercise stress testing, is the most common agent used to induce pharmaceutical stress in SPECT tests in the US; it was used off-label for the CT imaging.
Dr Ricardo C Cury (Baptist Hospital of Miami, FL) presented the trial results here at a late-breaking clinical-trials session at the Society of Cardiovascular Computed Tomography (SCCT) 2013 Scientific Meeting.
To heartwire, Cury noted that this trial established noninferiority of regadenoson stress CT perfusion to the reference method, regadenoson SPECT, to detect or exclude myocardial ischemia, which was the primary study outcome.
"This is the second multicenter trial validating [regadenoson] stress CT perfusion, which [builds on the accumulating supporting data from] many single-center studies," he said, adding that it is still too early, however, to implement these findings into clinical practice.
To heartwire, session moderator Dr John Hoe (Parkway Health Radiology, Singapore) commented that "this is quite an important multicenter trial . . . and the results look very good." Echoing Cury, he added that "this [research] is slowly [progressing] along the path to validate [regadenoson] CT perfusion as a technique to assess myocardial ischemia."
In study, 39% of patients had suspected CAD
This was a crossover study conducted at 11 sites in the US, using six types of CT scanners, including 64-, 128-, 256-, and 320-slice machines.
A total of 124 individuals with known (39%) or suspected CAD were randomized to either rest and stress SPECT using regadenoson on day 1, followed by rest and combined stress CT perfusion using regadenoson and coronary CT angiography on day 2; or the same tests in the reverse order.
At baseline, the subjects had a mean age of about 62 and an average body-mass index (BMI) of close to 30. Their average heart rate increased from 64 to 84 beats per minute with the stress-CT perfusion test.
Myocardial ischemia was defined as having two or more reversible defects.
High agreement, specificity, and sensitivity
When it came to detecting myocardial ischemia, CT perfusion imaging agreed with the findings of the reference method, SPECT, 87% of the time (95% CI 0.77-0.97).
"This was well above the specified primary end point for the agreement rate between SPECT and CT perfusion for the detection of ischemia," Cury said.
Stress CT perfusion imaging also had a high specificity (84%) and sensitivity (90%) for detecting or excluding myocardial ischemia.
Similarly, when it came to detecting the presence or absence of one or more fixed myocardial defects, CT perfusion imaging agreed with the results of the reference method, SPECT, 86% of the time (95% CI 0.74-0.98).
Again, stress CT perfusion imaging had a high specificity (95%) and sensitivity (77%) for detecting or excluding fixed defects.
Used alone, compared with the reference standard of SPECT, stress CT perfusion diagnosed or excluded ischemia accurately in 85% of cases, whereas CT angiography alone made the correct diagnosis in 69% of cases. Thus, "stress CT perfusion may add significant [diagnostic] value to CT angiography alone," Cury noted.
Regadenoson was well tolerated, and the most common adverse events were flushing or headache.
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