Optimizing the Technique for Invasive Fractional Flow Reserve to Assess Lesion-Specific Ischemia.

BACKGROUND

Invasive fractional flow reserve (FFR) is the standard technique for assessing myocardial ischemia. Pressure distortions and measurement location may influence FFR interpretation. We report a technique for performing invasive fractional flow reserve (FFR) by minimizing pressure distortions and identifying the proper location to measure FFR.

METHODS

FFR recordings were obtained prospectively during manual hyperemic pullback in 100 normal and diseased coronary arteries with single stenosis, using 4 measurements from the terminal vessel, distal-to-the-lesion, proximal vessel, and guiding catheter. FFR profiles were developed by plotting FFR values (-axis) and site of measurement (-axis), stratified by stenosis severity. FFR≤0.8 was considered positive for lesion-specific ischemia.

RESULTS

Erroneous FFR values were observed in 10% of vessels because of aortic pressure distortion and in 21% because of distal pressure drift; these were corrected by disengagement of the guiding catheter and re-equalization of distal pressure/aortic pressure, respectively. There were significant declines in FFR from the proximal to the terminal vessel in normal and stenotic coronary arteries (<0.001). The rate of positive FFR was 41% when measured from the terminal vessel and 20% when measured distal-to-the-lesion (<0.001); 41.5% of positive terminal measurements were reclassified to negative when measured distal-to-the-lesion. Measuring FFR 20 to 30 mm distal-to-the-lesion (rather than from the terminal vessel) can reduce errors in measurement and optimize the assessment of lesion-specific ischemia.

CONCLUSIONS

Meticulous technique (disengagement of the guiding catheter, FFR pullback) is required to avoid erroneous FFR, which occur in 31% of vessels. Even with optimal technique, FFR values are influenced by stenosis severity and the site of pressure measurement. FFR values from the terminal vessel may overestimate lesion-specific ischemia, leading to unnecessary revascularization.