How to evaluate stents and techniques for bifurcation stenting? Bench test : Is it still useful? Do we need standardization? Yoshinobu Murasato MD, PhD Dept. of Cardiovascular Medicine, New Yukuhashi Hospital murasato@shinyukuhashihospital.or.jp October 12-13, 2012, Barcelona
Bench testing: Benefits 1. Clear visualization of stent configuration after complex procedure 2. Assessment of stent platform Kissing balloon inflation, Proximal optimization technique, 2-stent technique Stress test (stretch, compression) 3. Assessment of stent performance Cross ability, Push ability, Conform ability 4. Assessment of polymer damage 5. Rheological assessment
Bench testing: Limitations 1. Difference in elasticity between vessel model and human coronary artery 2. Difficulty in the creation of atherosclerotic coronary model (stenosis, calcification) 3. 3-dimentional structure 4. Difficulty in assessment of the effect of heart beating 5. Only a part of stent assessment DES performance should be evaluated in the aspects of stent platform, polymer, and drug, respectively.
Progress of bench testing 1. Clear visualization Fluoroscopy, Endoscopy Murasato Y. CCI 2005, 66, 237 Ormiston JA. CCI 2004, 63, 332 Murasato Y, Colombo A, Moussa I Tips and Tricks in Interventional Therapy of Coronary Bifurcation Lesions
Micro focus CT Progress of bench testing 1. Clear visualization High resolution (0.06mm) can provide strut-level information. 3-D reconstruction Micro focus CT vs. IVUS in the worst case of crush stenting a b c d e f a b c d e f g h g h a b あ a b c d e c d Murasato Y, Colombo A, Moussa I Tips and Tricks in Interventional Therapy of Coronary Bifurcation Lesions e
Two overlapping styles in KBT Minimal overlapping + Proximal large ballooning ML Vision 3.5/28, 14atm SB Ryujin 3.0/20, 12atm KBT (6atm) MV Ryujin 3.5/20 SB Ryujin 3.0/20 prox MV Quntum Maverick II 4.5/8, 12atm Long overlapping ML Vision 3.5/28, 14atm SB Ryujin 3.0/20, 12atm KBT (6atm) MV Ryujin 3.5/20 SB Ryujin 3.0/20 Mitsudo s law 3.5 2 + 3.0 2 = 4.6 2 Murasato Y, EBC 2009
Minimal overlapping + Proximal large ballooning Long overlapping
Deformation of proximal MV stent after KBT Minimal overlapping + Proximal large ballooning Long overlapping
Resolute Integrity Long overlapping Minimal overlapping Integrity 3.0 / 22
Promus Element Long overlapping Minimal overlapping Promus element 3.0 / 24
S-stent 3.0/18 Nobori Long overlapping Minimal overlapping
Xience V Long overlapping Minimal overlapping ML Vision 3.0/23 ML Vision 3.0/18
Long overlapping vs. Minimal overlapping (mm) 6 5,5 Resolute Integrity Long X Long Y 6 5,5 6 Minimal X Minimal Y 5,5 6 5,5 Pedge Pmid Promus Element Nobori Xience V P0 5 5 5 5 4,5 4,5 4,5 4,5 4 4 4 4 3,5 3,5 3,5 3,5
Progress of bench testing 2. Realistic phantom model Material: silicone, polyvinyl acetate, plastic, acryl Tube or mold type Silicone tube Similar vascular elasticity Similar stenotic compliance as human coronary artery Post mortem heart 3-D silicone model reconstructed by CT information
Development of Stenotic Coronary Bifurcation: Elastic Three-Dimensional Model Handmade silicone tube Iwasaki K. TCTAP 2012 Similar vascular elasticity Similar stenotic compliance Average bifurcation angles in MDCT Kawasaki T. CCI 2009 LM-LAD 143, LM-LCX 121, LAD-LCX 72 150 LAD LMT LMT~LAD: 60% Stenosis 3.5mm 4mm 80 130 LCx: 50% Stenosis LCx 3mm
3-D silicone model reconstructed by MDCT Hikich Y, EBC 2009 LMCA: culotte LAD-diag: crush Limitation Validation of bifurcation lesion Vessel stiffness High cost
Loophole of bench testing Comparison in 2-step KBT for SB ostial dilation Ormiston JA. Euro PCR 2010 Stent cell size SBOS AS >3.5mm 52% <3.5mm 37% (p<0.001) 2-step KBT is more effective in large cell stents.
However, worse TLR in PES and ZES Crush stenting 20 TAP technique Target bifurcation failure (cardiac death, MI, restenosis, TVR) Loophole of bench testing: The bench test evaluated 10 only stent platform, and there is a risk of misinterpreting the 5clinical outcome. 15 Chen SL. Chin Med J. 2008 0 SES ZES EES Sgueglia GA. CCI 2011, CASTOR bifurcation registry
Novel assessment: Virtual bench testing Mortier P, Euro Interv 2011, 7, 369 Virtual stent dilation Actual dilation Virtual deployment in the curved vessel Axial stress distribution
Limitation of virtual bench testing Validation of devices Validation of vessels Validation of stent behavior depending on the coronary lesion Plaque thickness Vessel stiffness Stenosis Tortuosity Angle Distance from ostium
Is bench testing still useful? Yes! Simple lesion: Since there was no significant difference in clinical outcome among new-generation DESs, the assessment of the platform does not have a significant meaning. Complex lesion (LMCA, bifurcation, tortuous, calcified, ostial, CTO): Bench testing is still required for the evaluation of the platform and stent performance.
Bench testing is especially important Stent distortion Scaffolding, gap formation in LMCA bifurcation. Double stenting has been performed at 20-60%. KBT is mandatory after double stenting. Leaving the jailed struts without KBT remains controversial in the late-phase events. Stent overlapping, crossing, twisting Proximal overdilation Metal overlapping Damage of polymer of DES Effect of coronary flow, shear stress
Do we need standardization? Basic methodology should be commonly shared. Silicone system is preferable. Physiological model (3-D structure, vessel size according to branching law, bifurcation angle) is preferable. High-resolution imaging (i.e. microfocus CT, endoscopy, CCD camera, electron microscope) is necessary. Standardization of all techniques is difficult. Each technique has different benefits and limitations. An appropriate test should be adopted depending on the purpose of experiment.
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