Conference Coverage

Contrast injection approximates adenosine-derived FFR




PARIS – Measurement of fractional flow reserve using adenosine remains the gold standard for assessing the functional significance of coronary stenoses, but when that’s not an option then intracoronary infusion of contrast medium is a good alternative, according to the results of the CONTRAST trial.

“Contrast injection is an easy, inexpensive, and safe method of providing hyperemia. It displays excellent test/retest stability. And it does not depend on a specific software platform or ECG gating. So if you need to use it, all of you can start next week,” Dr. Nils P. Johnson said in presenting the CONTRAST study findings at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

Dr. Nils P. Johnson Bruce Jancin/Frontline Medical News

Dr. Nils P. Johnson

He was quick to emphasize that contrast measurement of Pd/Pa – that is, the pressure distal to a stenosis relative to the pressure proximal to a stenosis – had a diagnostic accuracy of 86% relative to adenosine-derived fractional flow reserve (FFR) as the reference standard in the CONTRAST trial. So the contrast-based measurement is imperfect, and interventionalists who use it run the risk of making the wrong clinical diagnosis. However, a key clinical finding in CONTRAST was that if the contrast-based Pd/Pa value was 0.8 or less, then the adenosine-derived FFR was, too, thus confirming the functional significance and actionability of the lesion under evaluation.

Adenosine maximizes hyperemia, and adenosine-derived FFR is the version of the test with a IA recommendation in European Society of Cardiology guidelines based upon the persuasive findings of the FAME and FAME 2 (N. Engl. J. Med. 2014;371:1208-17) studies. It is, Dr. Johnson stressed, the best technique, but inducing hyperemia via adenosine is expensive, time-consuming, and burdensome. And when it’s not an option, either because a patient has a contraindication to adenosine or a health care system deems adenosine prohibitively expensive as a first-line agent, then achieving hyperemia via an injection of contrast media is a reasonable strategy for measurement of Pd/Pa, according to Dr. Johnson, coprincipal investigator for the CONTRAST study and a cardiologist at the University of Texas, Houston.

He noted that in the study, contrast Pd/Pa proved to have a significantly better diagnostic accuracy than the 78%-79% achieved via measurement of Pd/Pa at physiologic rest or based upon the instantaneous wave-free rate (iFR), a proprietary Volcano Corp. technology that assesses a lesion’s significance over the course of five heartbeats without need for hypemic agents. Moreover, the contrast Pd/Pa’s test/retest stability was as good as with intracoronary or intravenous adenosine and superior to that of iFR or resting Pd/Pa.

CONTRAST was a 750-patient, nine-country, prospective diagnostic accuracy study. It was designed as a pragmatic, real-world study in which investigators utilized an average of 8.2 mL of any of eight contrast agents in assessing a variety of coronary lesions in consecutive patients. Thus, the results are broadly applicable to anyone who performs percutaneous coronary intervention (PCI), the cardiologist said.

Once the pressure wire was introduced into a participant in the CONTRAST study, measurement of Pd/Pa was obtained during two intracoronary contrast infusions, two intracoronary adenosine infusions, two intravenous adenosine infusions, twice at rest, and twice using iFR. The tracings were then sent to a core physiology lab for interpretation by blinded evaluators.

A study limitation was that investigators didn’t collect data on the incidence of contrast-induced nephropathy. However, with an average contrast dose of just 8.2 mL, it’s likely the clinical impact was negligible, according to Dr. Johnson.

The CONTRAST study was sponsored by the University of Texas Medical Center at Houston. Dr. Johnson reported receiving a research grant from St. Jude Medical to conduct the study.

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