Pressure wire versus microcatheter for FFR measurement: a head-to-head comparison

Recently developed microcatheters can be used instead of a pressure wire for fractional flow reserve (FFR) measurement. We sought to assess the haemodynamic and clinical impact of using a larger profile device to measure FFR.Our prospective registry included 77 consecutive patients who underwent invasive FFR measurement of intermediate coronary stenoses between June 2015 and July 2016. FFR values were obtained first using a pressure wire only (FFRw), second using a Navvus microcatheter (FFRMC), and finally using the wire with the microcatheter still in the stenosis (FFRw-MC) during intravenous adenosine infusion. Eighty-eight stenoses were suitable for a thorough head-to-head comparison. Mean FFRw (0.83±0.08) was significantly higher than mean FFRMC (0.80±0.10) and FFRw-MC (0.80±0.10). Mean FFRMC and FFRw-MC did not differ significantly. Bland-Altman analysis showed a bias of -0.03±0.05 for lower FFRMC values compared to FFRw values. Using a threshold of 0.80 for FFR, the indication for revascularisation would have differed when based on FFRMC versus FFRw in 20/88 (23%) of the lesions and 18/77 (23%) of the patients.FFR measured using a microcatheter overestimates stenosis severity, leading to erroneous indication for revascularisation in a sizeable proportion of cases.