March 14th, 2015
Assessing the Diagnostic PROMISE of CT Angiography
The CardioExchange Editors interview Pamela S. Douglas, lead author of the PROMISE study. The randomized study compared CT angiography (CTA) with functional exercise testing (standard exercise ECG, nuclear stress testing, or stress echo) in more than 10,000 patients with chest pain. Findings were presented at the 2015 American College of Cardiology meeting and published simultaneously in the New England Journal of Medicine.
During a mean 25 months of follow-up, incidence of the primary endpoint — a composite of death, MI, hospitalization for unstable angina, or a major procedural complication — was 3.3% in the CTA group and 3.0% in the functional-testing group (a nonsignificant difference). Findings were consistent across various subgroups. Within the first 3 months, 12.2% of the CTA group and 8.1% of the control group underwent cardiac catheterization. Among randomized patients, a finding of no obstructive CAD was significantly less common in the CTA group than in the control group (3.4% vs. 4.3%).
Mean radiation exposure was lower in the stress-test group than in the CTA group (10.1 vs. 12.0 milliSieverts), because 33% had testing without any radiation exposure. Among patients initially intended for referral to nuclear stress testing, radiation exposure was lower in those randomized to CTA than to functional testing (mean, 12.0 vs. 14.1 mSv).
CardioExchange Editors: Were you surprised by the results of this study?
Douglas: There were a lot of surprises in this study, starting with the risk burden in the population. Given the considerable discussion about appropriate use, we expected to enroll a fairly low-risk group. Instead, the pretest likelihood of obstructive CAD was over 50%. Patients were middle-aged, had an average of 2.4 major CV risk factors, and were symptomatic — so they definitely required testing according to current guidelines.
The next surprise was the low event rate — much lower than previously reported in similar cohorts, and lower than predicted. Even so, that’s great news for patients. Given the event rate, it would have been very difficult to identify a difference between the groups.
Two of the secondary endpoints were surprising:
- We expected CT angiography to be associated with more caths and revascularizations, which it was, but we were surprised by how much it improved the cath yield (the rate of finding obstructive CAD at cath).
- We also expected radiation exposure to be higher with CTA than with nuclear testing, but the mean was more than 2 milliSieverts less.
CardioExchange Editors: Given the study’s findings, how are you changing your practice?
Douglas: CTA is now proven to be a very viable alternative to functional testing. It should be considered a first-line tool for patients with stable chest pain.
JOIN THE DISCUSSION
How will the findings from Dr. Douglas’ study alter your practice?
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