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Intracoronary pressure measurements have improved assessment of angiographic intermediate coronary stenoses. Methodically, pressure equalization and actual measurements are frequently performed at different height levels, depending on the particular coronary territory analyzed. Considering a hypothetical influence of hydrostatic pressure and the supine position of the patient, differences in the results of intracoronary measurements between anterior and posterior vessels seem likely. The purpose of this study was to compare the results of intracoronary pressure measurements between anterior and posterior coronary territories. Intracoronary pressure measurements of 214 coronary stenoses in 158 patients were analyzed. Fractional flow reserve (FFR) was measured in all stenosis and instantaneous wave-free ratio (iFR) in 197 stenoses in 144 patients. Both FFR (0.79 vs. 0.87, p < 0.001) and iFR values (0.86 vs. 0.94, p < 0.001) were significantly higher in posterior compared to anterior coronary vessels. Patients with only anterior or posterior lesions did not differ regarding clinical or lesion characteristics, in particular coronary stenosis severity (62.5 vs. 61.6 %, p = 0.27). Results of intracoronary measurements were systematically higher in the posterior coronary vessels when compared with anterior vessels. This phenomenon was independent of coronary stenosis severity or any clinical characteristics in our study population.

Background An influence of hydrostatic pressure on intracoronary indices of stenosis severity in vitro was recently reported. We sought to analyze the influence of hydrostatic pressure, caused by the height difference between the distal and proximal pressure sensor after guidewire positioning in the interrogated vessel, on intracoronary pressure measurements in vivo.Methods and results In 30 coronary stenoses, intracoronary pressure measurements were performed in supine, left, and right lateral patient position. Height differences between the distal and proximal pressure sensor were measured by blinded observers. Measurement results of the position with the highest ("high") and lowest height difference ("low") were compared. In group "high", all measured indices were higher: mean difference of fractional flow reserve (FFR) 0.045 (SD 0.033, 95% CI 0.033-0.057, p Conclusions The study demonstrates a relevant influence of hydrostatic pressure on intracoronary indices of stenosis severity in vivo, caused by the height differences between distal and proximal pressure sensor.

Measurement of fractional flow reserve (FFR) has become a standard diagnostic tool in the catheterization laboratory. FFR evaluation studies were based on pressure recordings during steady-state maximum hyperemia. Commercially available computer systems detect the lowest Pd/Pa ratio automatically, which might not always be measured during steady-state hyperemia. We sought to compare the automatically detected FFR and true steady-state FFR. Pressure measurement traces of 105 coronary lesions from 77 patients with intermediate coronary lesions or multivessel disease were reviewed. In all patients, hyperemia had been achieved by intravenous adenosine administration using a dosage of 140 µg/kg/min. In 42 lesions (40 %) automatically detected FFR was lower than true steady-state FFR. Mean bias was 0.009 (standard deviation 0.015, limits of agreement −0.02, 0.037). In 4 lesions (3.8 %) both methods lead to different treatment recommendations, in all 4 cases instantaneous wave-free ratio confirmed steady-state FFR. Automatically detected FFR was slightly lower than steady-state FFR in more than one-third of cases. Consequently, interpretation of automatically detected FFR values closely below the cutoff value requires special attention.