Conference Coverage

Coronary CT FFR sharpens patient assessment in two studies



– Noninvasive assessment of fractional flow reserve (FFR) within coronary arteries using data collected by CT angiography again has been shown to provide important additional diagnostic information that better guides patient management.

Dr. Todd C. Villines of Georgetown University, Washington

Dr. Todd C. Villines

Results from two separate studies presented at a session of the annual congress of the European Society of Cardiology documented the added value in calculating FFR within individual coronary arteries using coronary CT angiography (CCTA) data in patients with coronary stenosis of intermediate severity. But results from a third study reported at the session failed to show CCTA-derived FFR (FFRCT) information was superior to a detailed CCTA study alone for patient assessment.

“The value of FFRCT is to reduce the number of patients who go to the cath lab. For patients with a stenosis of 60% that is not likely to have functional significance we can avoid catheterization and treat the patient medically. FFRCT is a valuable technology, but my concern is that currently it costs about $1,400 for this test,” commented Todd C. Villines, MD, a cardiologist at Georgetown University in Washington who was a discussant for the study. “Given the cost, we need to better define the patients on whom we use FFRCT and integrate it into clinical decision making,” Dr. Villines said in an interview.

Perhaps the best demonstration of the potential role for FFRCT came from a single-center study at Aarhus (Denmark) University with 3,674 patients with stable chest pain who underwent CCTA as their initial assessment for suspected coronary artery disease between May 2014 and December 2016. More than two-thirds of these patients had coronary stenoses of less than 30% and had no further assessment or treatment, and 11% had at least one coronary stenosis of at least 70% on CCTA and then had follow-up testing by either conventional angiography or myocardial perfusion imaging. The report at the congress focused on the 697 patients with an inconclusive result based on CCTA alone and at least one stenosis of 30%-69% who underwent FFRCT analysis, and focused specifically on 677 patients with a useful FFRCT result.

Of these patients, 410 (61% of this subgroup) had no coronary lesion that created a FFRCT of 0.8 or less. All received treatment with optimal medical therapy only, and after a median follow-up had a 3.9% incidence of the primary endpoint, the combined rate of all-cause death, nonfatal MI, hospitalization for unstable angina, or unplanned revascularization. This 3.9% rate was not significantly different from the 2.8% rate seen during follow-up of the patients with no coronary stenosis of 30% or greater.

The remaining 267 patients (39% of the subgroup) with a FFRCT that showed 80% or less flow reserve either received optimal medical therapy (112 patients, 42% of this group) or angiography by coronary catheterization (155 patients, 58% of this group).

Dr. Bjarne L. Nørgaard, Aarhus (Denmark) University Mitchel L. Zoler/MDedge News

Dr. Bjarne L. Nørgaard

During follow-up, the combined endpoint occurred in 6.6% of patients treated with invasive angiography and possibly a catheter-based intervention. That result was not statistically different from the patients without more severe stenoses, and in 9.4% of patients treated with optimal medical therapy was a statistically significant worse outcome than in the patients with less consequential coronary stenoses. Further analysis showed that the better outcomes in patients with meaningful stenoses treated with catheterization occurred because this strategy substantially reduced the rate of nonfatal MIs and unplanned revascularizations, reported Bjarne L. Nørgaard, MD, an Aarhus cardiologist. Major limitations of the study were that it ran at only a single center and had a relatively short follow-up, he noted. Concurrently with the congress report, an article with the results appeared online (J Am Coll Cardiol. 2018 Aug 25. doi: 10.1016/j.jacc.2018.07.043).

The second report used data collected from 5,083 patients entered into a multinational registry, ADVANCE, with symptoms suggestive of coronary artery disease and results from CCTA that suggested coronary stenosis. The collaborating researchers then used the CCTA results to generate a FFR analysis for 4,893 (96%) of the patients, and the analysis was usable for 4,737 of them. The FFRCT results led to reclassification of the management strategy for 67% of the patients, the primary endpoint for this analysis, reported Timothy A. Fairbairn, MD, a cardiologist at the Liverpool (England) Heart and Chest Hospital.

Dr. Timothy A. Fairbairn, Liverpool (England) Heart and Chest Hospital Mitchel L. Zoler/MDedge News

Dr. Timothy A. Fairbairn

The results also showed that stratifying patients by their FFRCT results significantly reduced the percentage of patients referred for invasive coronary angiography who had nonobstructive coronary disease. The results showed that 19% of patients with a FFR of at least 0.81 underwent invasive angiography, and 44% of those had nonobstructive disease. In contrast, among patients with a FFR of 0.8 or less, 56% underwent invasive angiography, which failed to find obstructive disease in just 14%, reported Dr. Fairbairn. In addition, none of the 1,592 patients with a FFRCT of at least 0.81 had a death or MI during 90 day follow-up, while among the 3,145 patients with a FFRCT of 0.8 or less, the 90-day death or MI rate was 0.3%, a statistically significant difference that calculated to a nearly 15-fold higher hazard ratio.

One limitation of this study was the relatively brief, 90-day follow-up, but it is the first real-world, multicenter assessment of the utility and safety of FFRCT.

These findings highlight what a “disruptive technology” FFRCT represents, commented Dr. Villines. He also noted that the reclassifications triggered by the FFRCT analysis led to fewer patients undergoing invasive angiography, a good outcome from a cost-effectiveness perspective.

Concurrently with Dr. Fairbairn’s report the results from ADVANCE also appeared in an article published online (Euro Heart J. 2018 Aug 25. doi: 10.1093/eurheartj/ehy530).

A third FFRCT study reported at the session, the Computed Tomographic Evaluation of Atherosclerotic Determinants of Myocardial Ischemia (CREDENCE) study, enrolled 612 patients with suspected coronary artery disease who had been referred for and underwent invasive coronary angiography with FFR evaluation at 13 international centers, including several in the United States. All 612 patients also had assessment by CCTA and FFRCT, and also some type of functional myocardial perfusion assessment using positron emission tomography, single-photon emission CT, or coronary MR.

Dr. Wijnand J. Stuijfzand, Weill Cornell Medical College, New York Mitchel L. Zoler/MDedge News

Dr. Wijnand J. Stuijfzand

The results showed that coronary evaluation by CCTA performed significantly better than functional testing. A receiver operator characteristic curve analysis showed an area under the curve of 0.83 for CCTA in the validation phase of the analysis, compared with 0.68 for myocardial perfusion assessment, showing significantly better diagnostic performance of CCTA, reported Wijnand J. Stuijfzand, MD, a cardiologist at Cornell University in New York. In this analysis, five key variables improved the diagnostic performance of the CCTA analysis: stenosis severity, the number of coronary lesions producing at least 30% stenosis, noncalcified plaque volume, the presence of high-risk plaque, and lumen volume. In this analysis, adding FFRCT information to a CCTA assessment that already included these five key elements did not further improve diagnostic performance, Dr. Stuijfzand said.

The Aarhus University study received no commercial funding. Dr. Nørgaard has received research funding from Edwards; Siemens; and HeartFlow, the company that markets FFR analysis for coronary CT angiography data. The ADVANCE registry was sponsored by HeartFlow. Dr. Fairbairn has been a speaker for Heartflow. Dr. Stuijfzand and Dr. Villines had no relevant disclosures.

Recommended Reading

Rotablation aids in prepping highly calcified lesions: PREPARE-CALC
MDedge Cardiology
IVUS guidance cuts target-vessel failure risk by 47%
MDedge Cardiology
FAST-FFR: Noninvasive FFR nearly as good as wire
MDedge Cardiology
Fish oil phoenix
MDedge Cardiology
Antithrombotic strategy 1 year after stenting in AF patients leans toward oral anticoagulant alone
MDedge Cardiology