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Coronary fractional flow reserve measurements of a stenosed side branch : a computational study investigating the influence of the bifurcation angle

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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 degrees, 55 degrees, and 70 degrees), 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 Delta P-SB-Q(SB) 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 (Delta P = 0.451*Q + 0.010*Q(2) and Delta P = 0.687*Q + 0.017*Q(2) for 40 degrees and 70 degrees 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 Delta P-SB-Q(SB) 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.
Keywords
WALL SHEAR-STRESS, BLOOD-FLOW, INTRAVASCULAR ULTRASOUND, CAROTID, BIFURCATION, BOUNDARY-CONDITIONS, HELICAL FLOW, VARYING CURVATURE, ARTERY CURVATURE, STENOTIC FLOWS, LESIONS, Coronary bifurcation, Fractional flow reserve, Pressure drop, Helicity, Computational fluid dynamics, Mathematical model

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Chicago
Chiastra, Claudio, Francesco Iannaccone, Maik J Grundeken, Frank JH Gijsen, Patrick Segers, Matthieu De Beule, Patrick W Serruys, Joanna J Wykrzykowska, Antonius FW van der Steen, and Jolanda J Wentzel. 2016. “Coronary Fractional Flow Reserve Measurements of a Stenosed Side Branch : a Computational Study Investigating the Influence of the Bifurcation Angle.” Biomedical Engineering Online 15.
APA
Chiastra, C., Iannaccone, F., Grundeken, M. J., Gijsen, F. J., Segers, P., De Beule, M., Serruys, P. W., et al. (2016). Coronary fractional flow reserve measurements of a stenosed side branch : a computational study investigating the influence of the bifurcation angle. BIOMEDICAL ENGINEERING ONLINE, 15.
Vancouver
1.
Chiastra C, Iannaccone F, Grundeken MJ, Gijsen FJ, Segers P, De Beule M, et al. Coronary fractional flow reserve measurements of a stenosed side branch : a computational study investigating the influence of the bifurcation angle. BIOMEDICAL ENGINEERING ONLINE. London: Biomed Central Ltd; 2016;15.
MLA
Chiastra, Claudio, Francesco Iannaccone, Maik J Grundeken, et al. “Coronary Fractional Flow Reserve Measurements of a Stenosed Side Branch : a Computational Study Investigating the Influence of the Bifurcation Angle.” BIOMEDICAL ENGINEERING ONLINE 15 (2016): n. pag. Print.
@article{8508304,
  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 degrees, 55 degrees, and 70 degrees), 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 Delta P-SB-Q(SB) 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 (Delta P = 0.451*Q + 0.010*Q(2) and Delta P = 0.687*Q + 0.017*Q(2) for 40 degrees and 70 degrees 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 Delta P-SB-Q(SB) 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.},
  articleno    = {91},
  author       = {Chiastra, Claudio and Iannaccone, Francesco and Grundeken, Maik J and Gijsen, Frank JH and Segers, Patrick and De Beule, Matthieu and Serruys, Patrick W and Wykrzykowska, Joanna J and van der Steen, Antonius FW and Wentzel, Jolanda J},
  issn         = {1475-925X},
  journal      = {BIOMEDICAL ENGINEERING ONLINE},
  keyword      = {WALL SHEAR-STRESS,BLOOD-FLOW,INTRAVASCULAR ULTRASOUND,CAROTID,BIFURCATION,BOUNDARY-CONDITIONS,HELICAL FLOW,VARYING CURVATURE,ARTERY CURVATURE,STENOTIC FLOWS,LESIONS,Coronary bifurcation,Fractional flow reserve,Pressure drop,Helicity,Computational fluid dynamics,Mathematical model},
  language     = {eng},
  pages        = {16},
  publisher    = {Biomed Central Ltd},
  title        = {Coronary fractional flow reserve measurements of a stenosed side branch : a computational study investigating the influence of the bifurcation angle},
  url          = {http://dx.doi.org/10.1186/s12938-016-0211-0},
  volume       = {15},
  year         = {2016},
}

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