The FAST-FFR trial, which was presented at the 2018 Transcatheter Cardiovascular Therapeutics (TCT) meeting (21–25 September, San Diego, USA) and published in Circulation, indicate that fractional flow reserve (FFR) derived from an angiogram (FFRangio, CathWorks) had high sensitivity, specificity, and diagnostic accuracy for predicting FFR values derived from a pressure wire. As FFRangio has the potential to be a faster and easier approach to physiological assessment than standard FFR, it may lead to greater use of FFR.
Presenting the data at TCT 2018, William Fearon (Stanford University School of Medicine, Department of Medicine, Stanford Cardiovascular Institute, Stanford, USA) noted that the use of FFR to guide treatment decisions is known to improve outcomes and has been incorporated in multiple guidelines, but added its use “remains lower than expected because of a number of potential issues including the extra time it takes, wire handling characteristics, pressure wire drift, the need for hyperaemia, and the expense”. Therefore, a system—such as FFRangio—that does not require a pressure wire or a hyperaemic agent may lead to increased used of FFR.
Rather than using a pressure wire, Fearon explained, FFRangio relies “on creating a 3D reconstruction of the coronary arterial system and estimating the resistance and flow at each point along the entire coronary tree”. “Preliminary studies have found that FFRangio, when measured offsite by experienced operators, correlates well with pressure wire-derived FFR,” he said. Thus, the aim of the FAST-FFR study was to further explore how FFRangio compared with FFR.
In the study, 301 patients (319 vessels) with stable angina, unstable angina, or non-ST-segment elevated acute coronary syndromes underwent FFR to assess a coronary stenosis. Their angiogram data were then used to calculate the FFRangio values; the hospital operator who calculated the FFRangio values (successfully measured in 98.7% of cases) was blinded to the FFR values. The sensitivity of the FFRangio (to the FFR values) was 93.5%, the specificity was 91.2%, and the diagnostic accuracy (overall) was 92%. Fearon noted the confidence intervals for these results were “well above the predefined performance goals”.
He concluded that FFRangio “may provide an easier and potentially faster method for performing physiology guided assessment of the overall coronary angiogram with similar accuracy to the reference standard, coronary pressure wire-based FFR,” adding that this may translate into “a greater percentage of patients undergoing physiologic guidance for revascularisation decisions and ultimately improve long-term outcomes”. However, he did acknowledge that “some important patient subsets”—including left main disease, low ejection fraction, and in-stent restenosis—were not included in the study and “will require further study”.
Fearon told Cardiovascular News: “To fully assess the clinical impact of FFRangio, a clinical outcomes study comparing it with wire-based FFR will be necessary.”