title: Coronary fractional flow reserve measurements of a stenosed side branch: a computational study investigating the influence of the bifurcation angle.
abstract: BACKGROUND
  Coronary hemodynamics and physiology specific for bifurcation lesions was not well understood. To investigate the influence of the bifurcation angle on the intracoronary hemodynamics of side branch (SB) lesions computational fluid dynamics simulations were performed.
  
  
  METHODS
  A parametric model representing a left anterior descending-first diagonal coronary bifurcation lesion was created according to the literature. Diameters obeyed fractal branching laws. Proximal and distal main branch (DMB) stenoses were both set at 60 %. We varied the distal bifurcation angles (40°, 55°, and 70°), the flow splits to the DMB and SB (55 %:45 %, 65 %:35 %, and 75 %:25 %), and the SB stenoses (40, 60, and 80 %), resulting in 27 simulations. Fractional flow reserve, defined as the ratio between the mean distal stenosis and mean aortic pressure during maximal hyperemia, was calculated for the DMB and SB (FFRSB) for all simulations.
  
  
  RESULTS
  The largest differences in FFRSB comparing the largest and smallest bifurcation angles were 0.02 (in cases with 40 % SB stenosis, irrespective of the assumed flow split) and 0.05 (in cases with 60 % SB stenosis, flow split 55 %:45 %). When the SB stenosis was 80 %, the difference in FFRSB between the largest and smallest bifurcation angle was 0.33 (flow split 55 %:45 %). By describing the ΔPSB-QSB relationship using a quadratic curve for cases with 80 % SB stenosis, we found that the curve was steeper (i.e. higher flow resistance) when bifurcation angle increases (ΔP = 0.451*Q + 0.010*Q (2) and ΔP = 0.687*Q + 0.017*Q (2) for 40° and 70° bifurcation angle, respectively). Our analyses revealed complex hemodynamics in all cases with evident counter-rotating helical flow structures. Larger bifurcation angles resulted in more pronounced helical flow structures (i.e. higher helicity intensity), when 60 or 80 % SB stenoses were present. A good correlation (R(2) = 0.80) between the SB pressure drop and helicity intensity was also found.
  
  
  CONCLUSIONS
  Our analyses showed that, in bifurcation lesions with 60 % MB stenosis and 80 % SB stenosis, SB pressure drop is higher for larger bifurcation angles suggesting higher flow resistance (i.e. curves describing the ΔPSB-QSB relationship being steeper). When the SB stenosis is mild (40 %) or moderate (60 %), SB resistance is minimally influenced by the bifurcation angle, with differences not being clinically meaningful. Our findings also highlighted the complex interplay between anatomy, pressure drops, and blood flow helicity in bifurcations.
authors: Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.|Laboratory of Biological Structure Mechanics (LaBS), Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Milan, Italy.
authors: Claudio
authors: C
authors: Chiastra
authors: Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.|IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium.
authors: Francesco
authors: F
authors: Iannaccone
authors: The Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors: Maik J
authors: MJ
authors: Grundeken
authors: Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.
authors: Frank J H
authors: FJ
authors: Gijsen
authors: IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium.
authors: Patrick
authors: P
authors: Segers
authors: IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium.|FEops bvba, Ghent, Belgium.
authors: Matthieu
authors: M
authors: De Beule
authors: International Centre for Circulatory Health, NHLI, Imperial College London, London, UK.
authors: Patrick W
authors: PW
authors: Serruys
authors: The Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors: Joanna J
authors: JJ
authors: Wykrzykowska
authors: Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.
authors: Antonius F W
authors: AF
authors: van der Steen
authors: Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands. j.wentzel@erasmusmc.nl.
authors: Jolanda J
authors: JJ
authors: Wentzel
mesh_terms: D001794:Blood Pressure; D023921:Coronary Stenosis / Q000473:pathology* / Q000503:physiopathology*; D003331:Coronary Vessels / Q000473:pathology* / Q000503:physiopathology*; D053805:Fractional Flow Reserve, Myocardial; D006439:Hemodynamics; D006801:Humans; D057446:Hydrodynamics; D008955:Models, Cardiovascular
keywords: Computational fluid dynamics; Coronary bifurcation; Fractional flow reserve; Helicity; Mathematical model; Pressure drop