Medical Device Consulting:

IVC Filter DesignBy Remy Doucet, Austin Shima, and

Jason Trimble

Objectives

• Analyze a current medical device (IVC filter) and determine pros and cons in treating disease (pulmonary embolism)

• Develop a design that improves upon the current medical device

• Analyze proposed design and explain mechanical forces that act upon the device and possible failure modes.

• Explain possible biological and chemical interactions with the body (biocompatibility)

Relevant Class Material

• Stress - normalization of forces through area

• Strain - the deformation of a material

• Fatigue - weakening of a material caused by repeated loading

• Biocompatibility - property of not eliciting response from living tissue

Important Definitions• Percutaneous - Done through the skin

s

• Endothelial cells - The cells that line the inside of blood vessels s

• Thrombosis - Formation of a blood clot that obstructs the flow of blood s

• Embolism - Any blockage of a blood vessel s

Background Pathology

• Deep Vein Thrombosis - A condition where blood clots form in the leg. h

• Pulmonary Embolism - A blood clot gets lodged in the lungs preventing blood flow from the lungs to the body.

Risk Factors

Risk Factors for DVT and Pulmonary Embolism include…• Prolonged bed rest or paralysis

• Sitting for long periods of time

• Being overweight

• Supplemental Estrogen

• Smoking

• Cancer

• Age

Personal or Family History of Deep Vein Thrombosis

Treatment Options • There are two major treatments for DVT and PE

- Blood Thinners or an IVC

• Blood thinners are the prefered treatment for DVT s

• If the patient cannot take blood thinners or they are not effective a doctor may advise the use of the Inferior Vena cava Filter as a last resort

- The filter is placed in the Inferior Vena Cava and any clots that may break off of the embolism will be caught by the Filter

• Usually removed after 5 years or may be removed if risk of DVT or PE is significantly reduced or if complications occur.

Current Device Faulty Loading Scenario

Multiple modes of failure to look out for with an IVC Filter.• Migration

• Tilting

• Fractures

• Perforation

• Embedding

https://www.youtube.com/watch?v=1djRpPxNGrA

Novel Design

Free Body Diagram

Design Considerations

• Integrated IVC is shaped into a bell-like shape vs traditional bacteriophage.

Conical bell shape provides more room for blood to flow around caught embolisms

• Outer stent structure for increased durability and greatly decreases chance of dislocation. Also provides increased blood flow.

• Stent structure can be equipped with localized blood thinning drugs

• IVC located near end of stent to allow for ease of placement and removal

Deployment Procedure

• Percutaneous deployment through femoral or jugular vein

• Advance rod through vein

• Release filter and device is ejected from catheter

• Insertion takes about 30 minutes

Material Properties of Invention● Nitinol or cobalt chromium alloy are good metals to use

○ Nitinol biocompatible and flexible with shape memory

○ Cobalt chromium corrosion resistant

● polymers

● Use drug - eluting stent

○ For preventing clots from blocking the vessel

Modes of Failure• Nitinol is flexible so will not fracture easily ( at about 250 MPa)

• Fatigue is more likely

- Stents are subjected to cyclic stresses following deployment

- Nitinol endurance limit of about 7 MPa at around 1 x 10^7 cycles

• Vessel can also be worn down

Importance of Retrievability

• Retrievability good for temporary high risk such as after surgery or trauma

• Can be a long-term risk of recurrent DVT

• Retrieved by clasping filter at end of catheter

• Retrieval rate affected by an inability to capture (device tilting, wall narrow)

• IVC filters have a lifetime of less than 5 years

• Stents are mainly permanent- for this design, endothelial cells can’t grow over it.

ReferencesAng, Hui Ying, 2017. Bioresorbable stents: Current and upcoming bioresorbable technologies.

International Journal of Cardiology 228, 931-939

Dixon, Austin, 2013. Improving retrieval rates for retrievable inferior vena cava filters. Expert Rev. Med. Devices 10(1), 135-141

Garcia, A., 2012. Evaluation of migration forces of a retrievable filter: Experimental setup and finite element study. Medical Engineering and Physics 34, issue 8, 1167 - 1176

Rundback, John H., 2010. Permanent or temporary IVC filtration with a novel double-ring anchoring technology optional nitinol filter. Expert Rev. Med. Devices 7(1), 11-19

Symptoms and causes - Pulmonary embolism. Retrieved from http://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/symptoms-causes/dxc-20234744

Xiong, Yonggang, 2016. Study of the Mechanical Properties and Biocompatibility of the Stents. Journal of Nanoscience and Nanotechnology vol. 16, 12214-12222

Questions?