Drug-Eluting Coronary Stents

By the Tovally Men:Todd Goodall Shiva Mehta

Aymen MaktariBilly Chen Max Cornell

April 17th, 2014

Overview

• Anatomy of Coronary Arteries

• Coronary Artery Disease (CAD)

• History of Treatments for CAD

• Form of the Promus Drug-Eluting Stent

• Function of the Promus Drug-Eluting Stent

Overview

• Materials of the Promus Drug-Eluting Stent

• Alternative Treatments for CAD

• Limitations of the Promus Drug-Eluting Stent

• Research and Development of Drug-Eluting Stents

• Design Recommendation for the Promus Drug-Eluting Stent

Introduction

• CAD kills 600,000 annually in the U.S.

• The drug-eluting coronary stent treats CAD.

• 640,000 stents are implanted annually in the U.S.

• Promus drug-eluting stent is a current model.

The Heart

Adapted from studyblue.com.

Right atrium

Right ventricle

Left ventricle

Left atrium

Aorta

Pulmonary artery

Coronary Arteries

Adapted from picstopin.com.

Right coronary artery

Left coronary artery

Posterior coronary artery

Aorta

Artery Cross-Section

Adapted from health.allrefer.com.

Smooth muscle

Inner lining

Exterior wall

Coronary Artery Disease

Adapted from heart.org.

Inner lining

Smooth muscle

Plaque

Normal Artery Narrowed Artery

Risk Factors for CAD

• High cholesterol• High blood pressure• Low physical activity• Unhealthy diet• Smoking• Old age• Genetics

Symptoms of CAD

• Angina

• Shortness of breath

• Rapid heartbeat

• Nausea

Causation of the Heart Attack

Adapted from myhealth.alberta.ca.

Cap Rupture Clot FormationCompletely Blocked Artery

Coronary Artery Bypass Grafting (1964)

Adapted from cardiosurgeon.co.uk and Healthwise Incorporated.

Vein graft from legInternal mammary artery graft

Coronary arteries

Before After

Balloon Angioplasty (1977)

Adapted from nhlbi.nih.gov.

Catheters

Plaque

Expandedballoon

Compressed plaque

Increased blood flow

Narrowed Artery

Widened Artery

Expanding Artery

Coronary Stents (1989 - Present)

Adapted from webmd.com and Healthwise, Inc.

Coronary stent

General Stent Structure

Connectors

Sciencedirect.com

Sinusoidal Rings

Stent Strut Cross-Section

Everolimus

PVDF-HFP Polymer

Platinum Chromium Platform

Collapsed Stent vs. Expanded Stent

Adapted from ev3.net

8 mm

2.25 mm

38 mm

4 mm

Coronary Angioplasty

Adapted from mayfieldclinic.com.

Aorta

Femoral artery

Catheter

Balloon Expansion

Adapted from hopkinsmedicine.org.

Coronary artery

Plaque

Balloon

Catheter

Guide wire

Collapsed Stent

Adapted from the British Heart Foundation.

Artery

Guide wire Stent

Plaque

Expanding Stent

Adapted from the British Heart Foundation.

Artery

Plaque

StentBalloon

Stent in Place

Adapted from the British Heart Foundation.

Plaque

Stent Artery

Drug release

Platinum Chromium Alloy Properties

Property Value UnitsYield Strength 480 MPaElastic Modulus 203 GPaCorrosion Resistance ExcellentBiocompatibility GoodDuctility 44.8% EL

PVDF-HFP Properties

Property Value UnitsElastic Modulus 0.44 GPaTensile Strength 24 MPaDegradation Period 6 MonthsBiocompatibility Excellent

Minimally Invasive Coronary Artery Bypass Grafting

Vein graft from legInternal mammary artery graft

Coronary arteries

Adapted from cardiosurgeon.co.uk and Healthwise Incorporated.

Incision Comparison

Traditional CABG Incision Minimally Invasive CABG Incision

Adapted from umm.edu

Bioabsorbable Coronary Stent

Adapted from REVA Medical, Inc.

Smooth Muscle

Plaque Stent

Stent Recoil

Inner Lining

Smooth Muscle

Plaque

Stent

Late Stent Thrombosis

Inner Lining

Smooth Muscle

Plaque

Stent

Blood Cells

Restenosis

Inner Lining

Smooth Muscle

Plaque

Stent

Tissue Overgrowth

Uneven Polymer Degradation

Drug

Polymer

Metallic Platform

Ideal Drug-Eluting Stent Properties

• High flexibility• High radial strength• Low toxicity• Bioactive nature• Consistent drug delivery

Non-Polymeric Stents

DrugMetallic Platform

Porous Surface

DrugMetallic Platform

Endothelial Progenitor Cell (EPC) Capture Stent

Antibody Coating Drug

Metallic Platform

Polymer Coating

EPC Capture Mechanism

Antigen

Endothelial Progenitor Cell

Antibody

Design Recommendation

Antibody Coating Drug

316L Stainless Steel Platform

Material ComparisonProperty Value Units (316L SS) Value Units (Platinum Chromium)Yield Strength 170 MPa 480 MPaElastic Modulus 193 GPa 203 GPaCorrosion Resistance Excellent ExcellentDuctility 40.0% EL 44.8% ELBiocompatibility Excellent Good

Advantages of the Design

Antibody Coating Drug

316L Stainless Steel Platform

Endothelial Cell

Summary

• Problem: CAD is the buildup of plaque in arteries.

• Solution: Drug-eluting coronary stents keep arteries open.

• Limitation: Arteries may still become blocked after stent implantation.

• Design Recommendation: A stent with a non-polymeric surface and an antibody coating prevents many problems.

References

• AllRefer (2010). Artery cut section. Retrieved April 15, 2014, from http://health.allrefer.com/pictures-images/artery-cut-section.html• American Heart Association (2009). Bioabsorbable coronary stents.

Retrieved April 15, 2014, from http://circinterventions.ahajournals.org/content/2/3/255/F1.expansion.html• British Heart Foundation (2012). Coronary angioplasty. London, Britain:

British Heart Foundation.• Boston Scientific Corporation (2009). The Element Stent Series. Retrieved

from http://multivu.prnewswire.com/mnr/bostonscientific/36501/docs/36501-Element_White_Paper.pdf

References

• Covidien (2013). Covidien. Retrieved March 12, 2014, from http://www.ev3.net/peripheral/intl/be-stents/paramount-mini-gps-balloon-expanding-peripheral-stent-system.htm• Crashing Patient (2011, July 14). Acute Coronary Syndromes.

Retrieved April 15, 2014, from http://crashingpatient.com/medical-surgical/cardiology/acute-coronary-syndromes.htm/• Healthwise (2013, April 17). How a Heart Attack Happens. Retrieved

April 1, 2014, from https://myhealth.alberta.ca/health/pages/conditions.aspx?hwid=zm2431

References

• Johns Hopkins Medicine (n.d.). Percutaneous Coronary Intervention (PCI), Coronary Angioplasty, and Stent Placement. Retrieved April 15, 2014, from http://www.hopkinsmedicine.org/healthlibrary/test_procedures/cardiovascular/percutaneous_transluminal_coronary_angioplasty_ptca_and_stent_placement_92,P07981/• Krasopoulos, G. (n.d.). Bypass (CABG) | Dr Krasopoulos. Retrieved March

4, 2014, from http://cardiosurgeon.co.uk/treatment-guide/bypass-cabg/• Minimally Invasive Cardiac Surgery. (2013, July 4). Retrieved from

http://filipinoinventionsanddiscoveries.blogspot.com/2013/07/minimally-invasive-cardiac-surgery-mics.html

References• NHLBI NIH (2012, February 1). How Is Coronary Angioplasty Done?

Retrieved April 15, 2014, from http://www.nhlbi.nih.gov/health/health-topics/topics/angioplasty/howdone.html• National Heart Lung and Blood Institute (2012, February 1). Explore coronary

angioplasty. Retrieved March 3, 2014, from http://www.nhlbi.nih.gov/health/health-topics/topics/angioplasty/• REVA Medical, Inc. (n.d.). Coronary Scaffold / REVA Medical, Inc. Retrieved

April 12, 2014, from http://www.teamreva.com/coronary-stent.shtml• StudyBlue (2014). Module 3 cardiovascular assessment and health promotion.

Retrieved April 16, 2014, from http://www.studyblue.com/notes/note/n/module-3-cardiovascular-assessment-and-health-promotion/deck/3911124• WebMD (2013, February 13). Coronary Stent. Retrieved April 15, 2014, from

http://www.webmd.com/heart-disease/coronary-stent