Fractional flow reserve derived from microcatheters versus standard pressure wires: a stenosis-level meta-analysis

AIMS: To determine the agreement between sensor-tipped microcatheter (MC) and pressure wire (PW)-derived fractional flow reserve (FFR). METHODS AND RESULTS: Studies comparing FFR obtained from MC (FFR(MC), Navvus Microcatheter System, ACIST Medical Systems, Eden Prairie, Minnesota, USA) versus standard PW (FFR(PW)) were identified, and a meta-analysis of numerical and categorical agreement was performed. The relative levels of drift and device failure of MC and PW systems from each study were assessed. Six studies with 440 lesions (413 patients) were included. The mean overall bias between FFR(MC) and FFR(PW) was −0.029 (FFR(MC) lower). Bias and variance were greater for lesions with lower FFR(PW) (p<0.001). Using a cut-off of 0.80, 18 % of lesions were reclassified by FFR(MC) versus FFR(PW) (with 15 % being false positives). The difference in reported drift between FFR(PW) and FFR(MC) was small. Device failure was more common with MC than PW (7.1% vs 2%). CONCLUSION: FFR(MC) systematically overestimates lesion severity, with increased bias in more severe lesions. Using FFR(MC) changes revascularisation guidance in approximately one out of every five cases. PW drift was similar between systems. Device failure was higher with MC.