Recently developed microcatheters can be used instead of pressure wire for fractional flow reserve (FFR) measurement. We sought to assess the hemodynamic and clinical impacts of using larger profile device to measure FFR.

Our prospective registry included 99 consecutive patients who underwent invasive FFR measurements of intermediate coronary stenoses between June 2015 and July 2016. FFR values were obtained first using a pressure wire only (FFR_w), second using a Navvus microcatheter (FFR_mc), and finally using the wire with the microcatheter still in the stenosis (FFR_w-mc) during intravenous adenosine infusion. Eighty-eight stenoses were suitable for a thorough head-to-head comparison. Mean FFR_w (0.83±0.08) was significantly higher than mean FFR_mc (0.80±0.10) and FFR_mc-w (0.80±0.10). Mean FFR_mc and FFR_mc-w did not significantly differ. Bland–Altman analysis showed a bias of −0.03±0.05 for lower FFR_MC values compared to FFR_w values. Using a threshold of 0.80 for FFR, the indication for revascularization would have differed when based on FFR_mc versus FFR_w in 20/88 (23%) of the lesions and 18/77 (23%) of the patients (Fig. 1).

FFR measured using a microcatheter overestimates stenosis severity, leading to erroneous indication for revascularization in a sizable proportion of cases.