The impact of hydrostatic pressure on the result of physiological measurements in various coronary segments.

The effect of hydrostatic pressure on physiological intracoronary measurements is usually ignored in the daily clinical practice. Our aim was to investigate this effect on Pd/Pa (distal/aortic pressure) and FFR (fractional flow reserve). 41 FFR measurements between 0.7 and 0.9 were selected. The difference in the height of the orifice and that of the sensor was defined in mm on the basis of 3D coronary reconstruction. Resting Pd/Pa and FFR were adjusted by subtracting the hydrostatic pressure gradient from the distal pressure. Height measurements were also performed from 2D lateral projections for each coronary segment (n = 305). In case of the LAD, each segment was located higher (proximal: - 13.69 ± 5.4; mid: - 46.13 ± 6.1; distal: - 56.80 ± 7.7 mm), whereas for the CX, each segment was lower (proximal: 14.98 ± 8.3; distal: 28.04 ± 6.3 mm) compared to the orifice. In case of the RCA, the distances from the orifice were much less (proximal: - 6.39 ± 2.9; mid: - 6.86 ± 7.0; distal: 17.95 ± 6.6 mm). The effect of these distances on pressure ratios at 100 Hgmm aortic pressure was between - 0.044 and 0.023. The correction for height differences changed the interpretation of the measurement (negative/positive result) in 5 (12%) and 11 (27%) cases for the FFR (cut-off value at 0.80) and the resting Pd/Pa (cut-off value at 0.92), respectively. The clinical implementation of hydrostatic pressure calculation should be considered during intracoronary pressure measurements. A correction for this parameter may become crucial in case of a borderline significant coronary artery stenosis, especially in distal coronary artery segments.