title: Effect of Coronary Anatomy and Hydrostatic Pressure on Intracoronary Indices of Stenosis Severity.
abstract: The authors sought to analyze height differences within the coronary artery tree in patients in a supine position and to quantify the impact of hydrostatic pressure on intracoronary pressure measurements in vitro.
  
  
  
  Although pressure equalization of the pressure sensor and the systemic pressure at the catheter tip is mandatory in intracoronary pressure measurements, subsequent measurements may be influenced by hydrostatic pressure related to the coronary anatomy in the supine position. Outlining and quantifying this phenomenon is important to interpret routine and pullback pressure measurements within the coronary tree.
  
  
  
  Coronary anatomy was analyzed in computed tomography angiographies of 70 patients to calculate height differences between the catheter tip and different coronary segments in the supine position. Using a dynamic pressure simulator, the effect of the expected hydrostatic pressure resulting from such height differences on indices stenosis severity was assessed.
  
  
  
  In all patients, the left anterior and right posterior descending arteries are the highest points of the coronary tree with a mean height difference of -4.9 ± 1.6 cm and -3.8 ± 1.0 cm; whereas the circumflex artery and right posterolateral branches are the lowest points, with mean height differences of 3.9 ± 0.9 cm and 2.6 ± 1.6 cm compared with the according ostium. In vitro measurements demonstrated a correlation of the absolute pressure differences with height differences (r = 0.993; p < 0.0001) and the slope was 0.77 mm Hg/cm. The Pd/Pa ratio and instantaneous wave-free ratio correlated also with the height difference (fractional flow reserve r = 0.98; p < 0.0001; instantaneous wave-free ratio r = 0.97; p < 0.0001), but both were influenced by the systemic pressure level.
  
  
  
  Hydrostatic pressure variations resulting from normal coronary anatomy in a supine position influence intracoronary pressure measurements and may affect their interpretation during stenosis severity assessment.
authors.affiliation: Department of Cardiology, Klinikum Oldenburg, European Medical School Oldenburg-Groningen, Carl von Ossietzky University Oldenburg, Germany. Electronic address: t.haerle@gmx.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Härle
authors.affiliation: Department of Cardiology, Klinikum Oldenburg, European Medical School Oldenburg-Groningen, Carl von Ossietzky University Oldenburg, Germany.
authors.forename: Mareike
authors.initials: M
authors.lastname: Luz
authors.affiliation: Department of Cardiology, Klinikum Oldenburg, European Medical School Oldenburg-Groningen, Carl von Ossietzky University Oldenburg, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Meyer
authors.affiliation: Department of Cardiology, Klinikum Oldenburg, European Medical School Oldenburg-Groningen, Carl von Ossietzky University Oldenburg, Germany.
authors.forename: Kay
authors.initials: K
authors.lastname: Kronberg
authors.affiliation: Department of Diagnostic and Interventional Radiology, Klinikum Oldenburg, European Medical School Oldenburg-Groningen, Carl von Ossietzky University Oldenburg, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Nickau
authors.affiliation: Cardiovascular Institute, Hospital Clinico San Carlos, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Escaned
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Justin
authors.initials: J
authors.lastname: Davies
authors.affiliation: Department of Cardiology, Klinikum Oldenburg, European Medical School Oldenburg-Groningen, Carl von Ossietzky University Oldenburg, Germany.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Elsässer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006328:Cardiac Catheterization / Q000295:instrumentation; D062906:Cardiac Catheters; D017023:Coronary Angiography / Q000379:methods*; D003326:Coronary Circulation; D023921:Coronary Stenosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D006874:Hydrostatic Pressure; D008297:Male; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D056888:Patient Positioning; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D016683:Supine Position; D014160:Transducers, Pressure
keywords: FFR; fractional flow reserve; iFR; instantaneous wave-free ratio