BACKGROUND: 

It is possible to simulate fractional flow reserve based on coronary angiographic cine acquisitions in several projections (FFR_angio). Several studies have demonstrated high accuracy of FFR_angio in comparison to invasively measured, pressure-wire derived fractional flow reserve (FFR). However, angiographic cine acquisitions with high frame rates (10 frames/s or more) have been used for such analyses. In clinical practice, lower frame rates (e.g., 7.5 frames/s) are often used to limit radiation exposure and it is not known whether lower cine angiographic frame rates negatively impact diagnostic accuracy of FFR_angio. 

METHODS:

A total of 50 patients who underwent invasive coronary angiography with clinically indicated invasive FFR measurement were prospectively included. Exclusion criteria included moderate or severe aortic stenosis, more than mildly reduced left ventricular ejection fraction (LV-EF <45%), previous PCI in the target vessel and poor contrast filling of the target vessel. Cine angiographic acquisitions of the target segment in 3 angulations at least 30° apart were obtained at 15 frames/s. FFR_angio was determined on an off-line workstation with proprietary software using original cine runs (FFRangio15) and based on runs articifially reduced to a frame rate of 7.5 frames/s. (FFR_angio7.5). Results were compared to FFR measured during intracoronary adenosine administration. Coronary stenoses with FFR ≤0.80 were classified as hemodynamically significant. Diagnostic results of FFR_angio15 and FFR_angio7.5 were compared to invasive FFR. 

RESULTS: 

Mean patient age was 64±17 years. Based on FFR, 15 lesions were hemodynamically significant. Median FFR across all 50 vessels was 0.89 (IQR 0.14). Median FFRangio15 was 0.89 (IQR 0.14) and median FFRangio7.5 was 0.87 (IQR 0.14) (both not significantly different from FFR). Correlation of FFR_angio15 and FFR_angio7.5 to invasive FFR was close (r=0.75, p<0.01 vs. r=0.69, p<0.01, respectively). Using a cut-off value of ≤0.8, FFR_angio15 displayed a sensitivity of 80% and a specificity of 94% to detect hemodynamically significant stenoses, resulting in a diagnostic accuracy of 90%. For FFR_angio7.5, sensitivity was 60% and specificity was 89% with a diagnostic accuracy of 80% (p = 0.16 compared to FFR_angio15).

CONCLUSION:

For calculation of FFR_angio, a frame rate of 15/s  provides numerically higher accuracy than a frame rate of 7.5/s for the assessment of the hemodynamic significance of coronary stenoses using invasive FFR as the gold standard.