AT ACC 2015

SAN DIEGO (FRONTLINE MEDICAL NEWS) – Initial anatomic testing with CT angiography yielded similar clinical outcomes to functional testing in chest pain patients evaluated for coronary artery disease in the PROMISE study.

After an average of 25 months, the primary composite end point of all-cause death, nonfatal myocardial infarction, unstable angina hospitalization, and major cardiovascular procedural complications occurred in 3.3% of the CTA patients and 3.0% of the functional-testing patients (adjusted hazard ratio, 1.04; P = .75).

The CTA strategy may offer a slight advantage, however, in terms of fewer invasive catheterizations without evidence of obstructive coronary artery disease (3.4% vs. 4.3%; P = .022) and a higher proportion of catheterizations with obstructive CAD (72.1% vs. 47.5%) getting revascularization (6.2% vs. 3.2%) or coronary artery bypass grafting (72 events vs. 38 events).

“Our results suggest that CTA is a viable alternative to functional testing. These real-world results should inform noninvasive testing choices in clinical care as well as provide guidance to future studies of diagnostic strategies in suspected heart disease,” lead study author Dr. Pamela Douglas reported at the annual meeting of the American College of Cardiology and simultaneously published online (N. Engl. J. Med. 2015 [ DOI:10.1056/NEJoa1415516 ].

PROMISE (Prospective Multicenter Imaging Study for the Evaluation of Chest Pain) enrolled 10,003 symptomatic outpatients requiring nonemergent, noninvasive testing for suspected CAD who were older than 54 years for men or older than 64 years for women with no risk factors, or aged 45-54 years for men and 50-64 years for women with at least one cardiac risk factor.

Patients were randomly assigned to anatomical testing with CTA or functional testing including a nuclear stress test (67%), stress echocardiography (23%), or exercise electrocardiogram (10%). The patients had an average of 2.5 risk cardiovascular risk factors and half were women.

Radiation exposure was higher overall in the CTA group than the functional-testing group (mean 12.0 mSv vs. 10.1 mSv; P < .001), largely because 33% of the functional group had no exposure. Exposure was lower, however, in CTA patients compared with those for whom a nuclear test was specified at randomization as their first intended functional test (12.0 mSv vs. 14.1 mSv; P < .001), Dr. Douglas , from Duke Clinical Research Institute in Durham, N.C., said.

During a discussion of the results, Dr. Elliott Antman , associate dean for clinical and translational research at Harvard University, Boston, said CT angiography can’t officially be described as noninferior to functional testing because PROMISE was designed as a superiority trial with a noninferiority margin that was exceeded by the confidence intervals for the primary end point and questioned how clinicians should use the results.

“What I can say to the next patient is that they can be incredibly assured about their overall prognosis, which is a nontrivial thing to say that they have a very, very low likelihood of a bad event in the next 2 years no matter what we do,” Dr. Douglas responded. “I can offer a test choice that will have no difference in major health events like death or nonfatal MI, but I can offer a test that potentially has lower radiation and has a better triage function to the cath lab where you have less likelihood of ending up in the cath lab not needing to be there because you do not have obstructive disease.”

Though PROMISE may influence practice, it is unclear whether the noninferiority issue will impact its ability to change U.S. guidelines, which currently include a IIb recommendation that CTA be considered in the evaluation of patients with chest pain.

“Technically two randomized controlled trials are needed before you get evidence level A, but we have 10,000 patients who were well studied here, so I would anticipate a big change actually in the guidelines from a use criteria, but we shall see,” Dr. Douglas said.