Accuracy of Fractional Flow Reserve Measurements in Clinical Practice: Observations From a Core Laboratory Analysis

Objectives The aim of this study was to compare site-reported measurements of fractional flow reserve (FFR) with FFR analysis by an independent core laboratory (CL). Background FFR is an index of coronary stenosis severity that has been validated in multiple trials and is widely used in clinical practice. However, the incidence of suboptimal FFR measurements is unknown. Methods Patients undergoing FFR assessment within the CONTRAST (Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology) study had paired, repeated measurements of multiple physiological metrics per local practice. An independent central physiology CL analyzed blinded pressure tracings off-line in a standardized fashion for comparison. Results A total of 763 patients were included in the study; 4,946 distal coronary artery pressure/aortic pressure (nonhyperemic) and FFR tracings were analyzed by the CL (mean 6.5 tracings per patient). Pull-back data were available for 616 patients (80.7%), of whom 108 (17.5%) had signal drift, defined as distal coronary artery pressure/aortic pressure (nonhyperemic) <0.97 or >1.03. Among the remaining 4,217 tracings without evidence of signal drift, 222 (5.3%) were noted to have ventricularization of the aortic waveform, and 168 (4.0%) had aortic waveform distortion. Excluding cases with signal drift and waveform distortion, there was excellent agreement between CL-calculated and site-reported FFR, with a mean difference of 0.003 ± 0.02. Predictors of distorted waveforms were smaller guiding catheter size (odds ratio: 6.30; 95% confidence interval: 3.22 to 12.32; p < 0.001) and intracoronary adenosine use (odds ratio: 0.13; 95% confidence interval: 0.05 to 0.33; p < 0.001). Conclusions This FFR CL analysis showed that almost 10% of tracings demonstrated waveform artifacts, and an additional 17.5% had signal drift. Among adequate tracings, there was a close correlation between site-reported and CL-analyzed FFR values. Attention to detail is critical for FFR studies to ensure adequate technique and optimal results.