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

AIMS: 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. METHODS AND RESULTS: 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. CONCLUSIONS: FFR measured using a microcatheter overestimates stenosis severity, leading to erroneous indication for revascularisation in a sizeable proportion of cases.

Clinical implications of guiding catheter extubation during fractional flow reserve measurements.

BACKGROUND: Fractional flow reserve (FFR) is defined by the maximal coronary flow ratio with and without stenosis. AIMS: We hypothesized that guiding catheter intubation in coronary ostia during FFR measurements may underestimate FFR value by limiting the increase of coronary flow during maximal hyperaemia. METHODS: Between June 2013 and January 2014, we prospectively included all patients with i.v. adenosine FFR measurements. FFR was measured with the guiding catheter intubated in the coronary ostia (FFRint) and extubated in the aorta (FFRext). We calculated the ratio between coronary ostium assessed by quantitative coronary angiography and guiding catheter surfaces, defined as the free ostial lumen ratio. RESULTS: In total, 151 lesions in 104 patients were included; 121 lesions and 88 patients were eligible for analysis. Mean±SD FFRext was significantly lower compared with FFRint; 0.82±0.08 and 0.84±0.08, respectively (P<0.001). Revascularization indication changed in 14 patients (16%). The difference induced by guiding extubation correlated significantly with the free ostial lumen ratio (R2=0.06, P=0.008). CONCLUSION: FFR value is significantly lower when the guiding catheter is extubated. The smaller the coronary ostium, the greater the difference observed between FFRext and FFRint. Guiding extubation during FFR measurements changed the revascularization indication in 16% of cases.