Treatment of lesions at bifurcations: General perspective

Transcription

1 ESC Congress August, Paris, France Treatment of lesions at bifurcations: General perspective Goran Stankovic MD, PhD, FESC Division of Cardiology Clinical Center of Serbia, Belgrade Serbia

2 Potential conflicts of interest Speaker s name: Goran Stankovic I do not have any potential conflict of interest

3 The fractal nature of vascular trees Kamiya and Takahashi. J Appl Physiol March 8, 2007 The branching systems in our body (vascular and bronchial trees) and those in the environment (plant trees and river systems) are characterized by a fractal nature. Fractal geometry: Mandelbrot Definition of FRACTAL : any of various extremely irregular curves or shapes for which any suitably chosen part is similar in shape to a given larger or smaller part when magnified or reduced to the same size

4 The fractal nature of vascular trees d2 m d1 d3 Fractal structures are composed by recursive pattern reproduced to generate invariable self-similarity regardless of the scale of observation. Finet Kamiya and Takahashi. J Appl Physiol March 8, 2007

5 The fractal nature of vascular trees m d1 Blood-flow distribution dictates vascular geometry; d3 d2 The law of conservation of mass: the sum of the outflows from bifurcation equals inflow; Relation between function (blood flow) and geometry (crosssectional area and diameter)

6 Structure-function scaling laws of vascular trees Flow / diameter relationship Kassab Am J Physiol 290: H ,2006

7 Structure-function scaling laws of vascular trees Flow-length relation Kassab Am J Physiol 290: H ,2006

8 Structure-function scaling laws of vascular trees Uniform size of terminal branches Number of terminal branches proportional to proximal diameter Perfused myocardial volume also proportional to proximal diameter (Index of MI) Kamiya and Takahashi. J Appl Physiol March 8, 2007

9 Bifurcation branching laws The 3 Diameters Murray s law D 1 3* = D2 3* + D3 3* Finet s law D 1 = 0.67(D 2 + D3) D 1 D 2 D 1 D 2 D 3 * 2.3 HK law D 3 MV diameter preserved before and after SB origin Self replicating From Koo, EBC, 2008

10 Rules of Bifurcation Diameters where Dm, Dl and Ds are diameter of mother, larger and smaller daughter vessels, respectively. Murray and HK models are based on minimum energy hypothesis. Area-preservation and Finet Models are empirical and do not have a physical basis.

11 Question If the diameters of two segments of a bifurcation are known, can an optimum diameter of the third diseased segment be determined?

12 Diameter Relation in HK Model Dm: Dl: Ds: Calculate Example: where Dm, Dl and Ds are diameter of mother, larger and smaller daughter vessels, respectively.

13 The 3 Diameters The main branch stent should be sized according to the distal main vessel diameter. Postdilatation, or kissing balloon inflations, are required to optimise the proximal main vessel stent diameter.

14 Courtesy of Koo et al. Carina Shifting

15 Carina Shifting Pre-intervention MB stenting Kissing balloon Koo et al EBC 2008

16 Bifurcation PCI: What Are The Main Objectives? To Restore the natural configuration (fractal) of the bifurcation: Optimal rheology; Stent well apposed Easy access in the future;

17 Proximal Optimisation Technique: POT in Provisional Side Branch Stenting D1 * D2 D3 POT

18 POT plus Simultaneous Kissing balloon post dilatation (MFCT) Kissing balloon post dilatation + POT (Kaname R )

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20 Law of Bifurcation D mother D daughter D daughter Murray s law HK law Area-preservation law Finet s law Flow law,. 20

21 Types of Involvement of Coronary Bifurcations by Atherosclerosis Atherosclerosis occur predominantly close to bifurcation Carinal involvement by atherosclerosis is extremely unusual. Renu Virmani

22 Flow Patterns and Spatial Distribution of Atherosclerotic Lesions in Human Coronary Arteries 1. Slow flow; 2. Low and oscillatory shear stress. Asakura and Karino, Circulation Research 1990;66:

23 Bifurcation and Flow Modifications Inner wall Centrifugal force Caro et al, 1978 Taken from G. Giannakoulas (EBC 2008)

24 Low ESS is a Major Stimulus for Atherogenesis and Plaque Progression Giannoglou GD, et al. Int J Cardiol 2002;86:27 Ku DN, et al. Arteriosclerosis 1985;5:293 Gimbrone MA, et al. Ann N Y Acad Sci 2000;902:230 Wentzel JJ, et al. Circulation 2003;108:17 Cheng C, et al. Circulation 2006;113:2744 Gambillara V, et al. J Vasc Res. 2005;42:535 Stone PH, et al. Circulation 2003;108:438

25 Lateral Walls of Bifurcations Susceptible to Atherosclerosis Nakazawa G, et al. JACC 2010

26 Is Carina Free of Atherosclerosis? Plaques at the flow divider, which is exposed to high WSS, are always accompanied by plaques in lateral walls (low WSS region), where plaques are supposed to originate from Van der Giessen, et al. Euroint 2008 Nakazawa G, et al. JACC 2010

27 Role of the Angulation A A B B A = + 33 after wiring B = Higher risk of SB occlusion Y. Louvard et al. TCT 2003 Y. Louvard et al. ESC 2004

28 Effect of Bifurcation Angle on Flow Perturbations and Atherosclerosis Increased bifurcation angle intensifies flow perturbations and low ESS environment in the lateral walls rendering them more susceptible to atherosclerosis Lower ESS Narrower angle Wider angle Markl M, et al. Circ Cardiovasc Imaging 2010

29 Bifurcation Stenting may alter local hemodynamic conditions Non-stented bifurc Stented bifurc Non-stented bifurcations Lateral walls low ESS atherosclerosis Flow divider high ESS reduced atherosclerosis Stented bifurcations Lateral walls low ESS NIH Flow divider low ESS NIH Nakazawa G, et al. JACC 2010

30 Computational flow dynamics pre and Focus on 60 Bifurcation : post bifurcation stenting Natural LM : Provisional stenting Stagnation zones, low velocities gradient, low shear stress, recirculation zones More pronounced 3D phenomenon

31 Stent-induced flow alterations WSS OSI Dynamically changing local ESS environment after stenting of the main vessel and side branch balloon angioplasty Williams AR, et al. J Appl Physiol 2010

32 Conclusions The design of coronary vasculature obeys the minimum energy hypothesis (principle of economy or efficiency); A set of scaling laws relates geometry/morphology (e.g., diameter, length and volume) and function (e.g., flow); If the diameters of two segments of a bifurcation are known, an optimum diameter of the third diseased segment be determined (Finet law);

33 Conclusions Atherosclerosis occurs predominantly in the lateral walls of bifurcations while carina is free of de novo atherosclerosis; MB stenting and SB angioplasty may alter the local hemodynamic conditions; Once over-expanded, additional stenting or kissing balloon inflation does not completely restore local hemodynamic conditions. Keeping the natural law of bifurcation (or fractal ratio) can reduce the amount of flow disturbance.

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