Coronary Bifurcations Lesions
From Basics to Classifications
José A. G. ÁLVAREZ MD FSCAI
Head of Interventional Cardiology
HOSPITAL ALEMAN
HOSPITAL BRITÁNICO DE BUENOS AIRES
Buenos Aires - Argentina
The basics: hidrodynamics
The basics:
Structure – function relation in the Coronary tree
Finet G et al Eurointervention 2010 (6) Suppl J : 110-115
The basics:
Structure – function relation in the Coronary tree
Murray´s law
r1³ = r2³ + r3³
Murray CD, 1926, Proc Natl Acad Sci., USA; 12:207-214
Diameter relationship of the three
segments of a bifurcation.
Bifurcation diameter
models
Murray (1926)
Relationship
Physical
mechanisms
r 1³ = r 2³ + r 3³
Minimum Energy &
WSS ~ Constant
7/3
= Dl
7/3
+
7/3
Ds
Huo and Kassab (HK)
Dm
Minimum Energy
Finet
Dm=0.678×(Dl+Ds)
“Fractal”-type relation
Area-preservation
D²m=D²l+D²s
Velocity ~ Constant
Dm, Dl, and Ds are the diameters of mother, larger and smaller daughter
vessels, respectively.
Yunlong Huo PhD et al, Eurointervention 2012; 7(11):1310-1316
ie.: Ds/Dl = 2.5/3.0 = 0.83
Schematic representation
of bifurcations with (A)
large and (B) small daughter
diameter ratios.
ie.: Ds/Dl = 1.5/3.2 = 0.47
Yunlong Huo PhD et al, Eurointervention 2012; 7(11):1310-1316
Yunlong Huo PhD et al, Eurointervention 2012; 7(11):1310-1316
http://www.et.iupui.edu/cnc/refdiacalculation.aspx
Diameter relationship of the three
segments of a bifurcation.
The stepwise difference between mother and
large daughter vessels is a fundamental
parameter for the prediction of incomplete
apposition of stent strut, which was observed
in more than 60% of non left main bifurcation
lesions.
Yunlong Huo et al, Eurointervention 2012; 7(11):1310-1316
Costa RA et al, J Am Coll Cardiol 2005;46:599-605
Finet G et al. Eurointervention 2008; 3: 490-498
Shear Stress (tensión de corte o deslizamiento)
Shear stress is the stress component parallel to a given surface,
such as a fault plane, that results from forces applied parallel to
the surface
Endothelial Shear Stress (ESS) is the tangencial force exerted on the
endothelial surface which results from the friction of the flowing blood.
ESS = µ . Dv/dy
(valid only for laminar flow)
G. Giannoglou et al , EuroIntervention 2010 Vol. 6 (Supplement J) J16-J23
Blood flow
direction
Velocidad en m/seg
0.02
0.14
Low and oscillatory WSS
High WSS
ESS (Pa)
Low and oscillatory WSS
0 0.65
1.3
Finet G et al Eurointervention 2010 (6) Suppl J : 110-115
The basics: summary
• Coronary bifurcations are transitional junctions that
allow the divergence of the system to nourish the
myocardium.
• The complexity of the tree consists of a pattern of
branching based on energetic efficiency (principle
of minimum work for blood transport).
• The bifurcation is a strategic nexus of geometry,
fluid dynamics and rheology.
Endothelial Shear Stress
and Atherosclerosis
ESS = µ x dv/dy (Pascal or dyne/cm2)
A, Change in plaque area in low–, intermediate–, and high–wall shear stress (WSS) segments
over 6 months.
Samady H et al. Circulation 2011;124:779-788
Copyright © American Heart Association
Plaque distribution in a bifurcation
Myocardial walls
Carina
Lateral walls
Epicardial walls
G. Giannoglou et al , EuroIntervention 2010 Vol. 6 (Supplement J) J16-J23
Plaque distribution in a bifurcation
High shear
Low shear
Necrotic Core Thickness (mm)
Plaque thickness
High shear
Low shear
Virmani R et al , EuroIntervention 2010 Vol. 6 (Supplement J) J16-J23
Shear Stress and atherosclerosis
LAMINAR FLOW NORMAL
LAMINAR FLOW DISTURBED
NON LAMINAR FLOW
Mechanotransduction
ACTIVATED INTRACELLULAR SIGNALLING PATHWAYS
GENE ACTIVATION
ALTERED ENDOTHELIAL CELL FUNCTION/MORPHOLOGY
Systemic
Risk Factors
ATHEROSCLEROTIC
PLAQUE
Genetic
Factors
Shear Stress and atherosclerosis: molecular, cellular
and vascular effects of low ESS
The pathogenesis of the atherosclerotic plaque is modulated by ESS regulation of
atheroprotective and atherogenic influences, by systemic risk factors and by genetic
influences that affect both multiple cellular processes in the wall and the plaque.
Endothelial Shear Stress and atherosclerosis
• Endothelial shear stress is the main flow-related factor
affecting the distribution of atherosclerosis in a bifurcation.
• Plaques are more prevalent in low ESS areas such as the
lateral walls of the main vessel and side branches, while
are less common in the carina.
• The carina is not free of atheroma and is affected in up to
one third of cases, but never in isolation. Lesions in the
carina are likely to develop as a result of circumferential
expansion of plaques from the lateral wall.
G. Giannoglou et al , EuroIntervention 2010 Vol. 6 (Supplement J) J16-J23
1.- How to define a bifurcation lession
European Bifurcation Group.
Cath Cardiovasc Interv2008; 71:175–183
2.- How to define “side branch” and
“distal main branch”.
• Nosological: LAD, Cx and PDA are always the
Distal Main Branch in relation to Diagonal,
Septal, Marginal and Posterolateral arteries
(but usually Mg are larger than distal Cx)
• QCA: the largest of the distal branches is the
Distal Main Branch.(but may be inconsistent with real
physiological significance).
• Technical: SB is the branch with the shortest
plaque.
3.- How to classify a bifurcation lesion
No differentiation is made between a normal segment
(lesion free segment) and a <50% stenosis
Calcifications?
Angulations (> or< 70°)?
Lesion length is SB?
TIMI flow in SB?
4.- MADS classification of dedicated devices
• M: Main proximal branch first
Axxess self expanding (Biosensors)
• A: main Across side first
Nile Crocco – Nile Pax (Minvasys)
• D: Distal first
• S: Side branch first
Sideguard (Capella Med Dev.)
Tryton Side Branch System
5.- Classification of TreatmentTechniques.
Louvard et al Cathet Cardiovasc Interv 2008; 71(2):175-183
Thank You for your
attention
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