The story of the coronary stent

RAMACHANDRA

PREFACEPCI is the most common procedure for cardiologistPOBA limited by dissections/ recoil/neointima/vessel closure/restenosisBMS limited by neointima[ISR- in 20%-30% of]DES limited by late stent thrombosis(Polymer without drug preventing endothelialisation)BVS limited by cost, long experience is awaited

POBAFirst successful balloon angioplastySeptember 16, 1977Zurich, Switzerland Andreas Gruentzig

STENTThe term “stent” derives from a dental prosthesis developed by the London dentist Charles Stent (1807–1885),indicate any device used for “extending, stretching, or fixing in an expanded state

The first stents were implanted in human coronary arteries in 1986 by Ulrich Sigwart, Jacques Puel, and colleagues, who placed the Walls stent sheathed self-expanding metallic mesh scaffold (Medinvent, Laus-anne, Switzerland) in the peripheral and coronary arteries of eight patients

Cesare Gianturco and Gary Roubin developed a balloon-expandable coil stent consisting of a wrapped stainless steel wire resembling a clamshell

A phase II study evaluating the Gianturco-Roubin stent to reverse POBA in acute or threatened vessel closure was started in 1988, ultimately leading to United States Food and Drug Administration (FDA) approval for this indication in June 1993

Julio Palmaz stent devised a balloon-expandable slotted stainless steel stent with rectangular diamond shaped slots is the mother of all the modern stents.

Gianturco-Roubin stent: Outdated

Cesare Gianturco and Gary Roubin developed a balloon-expandable coil stent consisting of a wrapped stainless steel wire resembling a clamshell

Palmaz-Schatz stent

First coronary Palmaz-Schatz stent was placed in a patient by Eduardo Sousa in São Paulo, Brazil in 1987 with a US pilot study started in 1988,is the mother of all recent stents((Johnson and Johnson Interventional Systems, Warren, NJ) )

Palmaz-Schatz stent Palmaz-Schatz stent, the first stent approved by the USFDA was introduced by Johnson and Johnson (J&J) in 1994

First stent trial(s) 1989, two randomized multicentre studies (STRESS and BENESTENT) comparing POBA to elective Palmatz-Schatz stenting. In these studies, 20% to 30% reduction in clinical and angiographic restenosis compared with POBA. Palmatz-Schatz stent approved by the FDA in 1994

The era and aura of DAP -1990Antonio Colombo :reduced rates of stent thrombosis using

1.IVUS

2.routine high-pressure (>14 atmospheres)

3.Aspirin and a second antiplatelet(thienopyridine, ticlopidine) vs. warfarin

Stent Design Composition of strut: Metallic or polymeric Configuration: Slotted tube versus coiled wire Bioabsorption:Durable or bioabsorbable Coatings :None/ passive such as heparin/ PTFE Bioactive :Eluting rapamycin or paclitaxel in pores in the stent wall or in polymer Implantation:Self-expanding or balloon-expandable

Stent CompositionNon-self expanding :stainless steel- 100 to 150 μm thick and Cobalt chromium/ platinum chromium alloys - lower-profile/ thin stent struts ( 75 ∼μm)

Self expanding: Nitinol, a nickel/titanium alloy that has super-elastic

Biodegradable stents:

1.Polymer of L-lactic acid (PLLA)

2. Non-polymeric :magnesium

Stent Configuration and Design

DesignWire coils: First Gianturco-Roubin stent but later all three designs failed(Poor radial and

axial strength)-outdatedSlotted tubes/multicellularModular designs

Stent lengths (8 to 48 mm) and diameters (2.25 to 6.0 mm) The initial modular stent was the Arterial Vascular Engineering Micro-Stent (subsequently

purchased by Medtronic Corp., Santa Rosa, CA), which had a series of 4-mm-long, rounded stainless steel corrugated ring subunits welded to each other. Subsequent designs have incorporated an ellipto-rectangular (rounded) strut profile and progressively reduced the length of the individual modules, with progressive reductions in crossing profile and increased surface area coverage.

Most of current stent from original Palmatz’ stent

ConfigurationDepending on the cellular configuration, multicellular stents can be broadly sub classified as either open cell or closed cell.

Open cell (Not all struts interconnected, open area >5mm²) designs tend to have varying cell sizes and shapes along the stent, and provide increased flexibility, deliverability, and side branch access by staggering the cross-linking elements to provide radial strength. Open cell designs thus tend to conform better on bends, though the cell area may open excessively on the outer curve of an angulated segment

Closed cell (Interconnected stent struts, open area <5mm²) designs typically incorporate a repeating unicellular element that provides more uniform wall cover-age with less tendency for plaque prolapse, at the expense of reduced flexibility and side branch access. Closed cell designs also tend to straighten vessel bends more than open cell designs.

Stent coating to stop ST

Balloon-Expandable Versus Self-Expanding StentsBalloon-expandable 1.Typically 1 to 1.1 times the reference arterial diameter 2.Length several millimetres longer than the lesion 3.. Almost all stents implanted in human coronary arteries

Self-expanding

1.Unconstrained diameter 0.5 to 1.0 mm greater than the adjacent reference segment to ensure contact with the vessel wall and adequate expansible force to resist vessel recoil

2. Final optimization of stent expansion usually requires additional dilatation within the stent using a high-pressure, noncompliant angioplasty balloon

3. Only few in use like The Cappella Sideguard Coronary Sidebranch stent

IndicationElectiveBail-out

BMSCoronary restenosis became known as the “Achilles’ heel” of coronary stenting20-30% at 6 months ISRBetter than POBA[STRESS and BENESTENT-1 ]

BMS is better

Metaanalysis from 13 randomized controlled trials of bare-metal stents compared to balloon angioplasty in acute myocardial infarction in 6,922 patients (adapted from De Luca et al., Int J Cardiol 2008)

DES

DRUGS

Generations of Drug-Eluting Stents

Mortality using DES vs. BMS:Not difference

3RD Generation 3rd generation strut 3rd generation polymer 3rd generation drugs

Platinum chromium alloy biodegradable polymers, polymer-free stents, and biodegradable stents on the basis of poly-L-lactide (PLLA) or magnesium

ZotarolimusEverelimus

Absorb, the 4th Revolution in Interventional Cardiology

Absorb defines a new paradigm - Vascular Reparative Therapy (VRT). VRT is designed to restore the vessel to a more natural state§, making natural vascular function possible

BVS:?Is the future

Implant Tech:The operator’s skillGuide catheter Guide wireStent selection Adjunctive :IVUS,FFR, OCT,atherectomy, thrombectomy and distal protection devices

Complication of stentingThrombosisPerforation(0.2% to 1.0%;balloon size>120% )DissectionInfectious EndarteritisAllergic ReactionsStent embolizationSide branch occlusion

Immediate complication of Stenting is ST

Risk factors for stent thrombosis

Minimum duration of DAP is 1 year

Bifurcation Stenting

20% or more of stenosisIncreased procedural complicationsDES in main vesselTrue bifurcation (+side branch >2mm

and diseased)Provisional stenting(main vessel

stented first)

Strategies for bifurcation disease: Louvard et al., Heart 20041 & 2. Classic T-stenting beginning with side branch stenting

3. Modified T-stenting=Mini crush

4. “Crush” technique

5. Classic T-stenting beginning with main branch stenting

6. Provisional T-stenting

7. Culottes' or trousers

8. Touching stents completed or not as Y technique

9.Trouser legs and seat

10. SKS

11. Skirt

Dedicated bifurcationNILE PAX BIFURCATION STENT[Heart Beat intervention Pvt. Ltd. ]

The Axxess stent (Devax Inc., CA, USA)

The SLK-View™ stent (Advanced Stent Technologies, CA, USA)

Tryton Side-Branch Stent (Tryton Medical, Inc., MA, USA)

The Stentys™ coronary stent (Stentys SAS, Paris, France)

ConclusionStent but no in-stent restenosis or stent thrombosisDIOR?No polymer if no more drug(Prof Renu Vira mani-2013) Does the future lies in BVS?

Test is dark hour