BME. Lesson Title. Grade Level. Stent Design 6-8

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BME Lesson Title Stent Design Grade Level 6-8 Authors Dr. Brian Davis, Dr. Carin Helfer Purpose This activity aims at using everyday materials to design and develop stents to unclog blood vessels.

animals) Balloon hand pump Time for Activity The activity can take 3 5 days depending on the amount of information on the heart and heart attacks that is discussed.

1 BME Lesson Title Stent Design Grade Level 6-8 Authors Dr. Brian Davis, Dr. Carin Helfer Purpose This activity aims at using everyday materials to design and develop stents to unclog blood vessels. Materials For each stent: o Paper (preferably graph paper) o Stent Example Template o Scissors or X- acto knife with cutting board o Tape Several 260Q balloons (thin, long balloons for balloon animals) Balloon hand pump Time for Activity The activity can take 3 5 days depending on the amount of information on the heart and heart attacks that is discussed. An estimate of the time required for each section is as follows: Engagement: Approximately one 45 minute class period Exploration: 20 minutes Explanation: minutes depending on the length of the discussion Elaboration: Option 1: minutes Option 2: The time required depends on the amount of time the students are given during the class period to do their research. Objectives Students will learn about the heart, coronary artery disease, heart attacks, and treatments for coronary artery disease. Students will learn about the circulatory system and biomedical engineering. Students will understand the use of cardiovascular stents to open arteries. Students will be able to define the criteria and constraints for designing a cardiovascular stent. Optional: Students will learn about fluid flow rate, resistance to flow, viscosity, and Poiseuille s Law.

2 Procedure Engagement Have a discussion about heart attacks. Ask the students what they know about this medical condition. Review the basics of the anatomy of the heart (see Useful Resources section for websites with information on the heart and heart attacks). Students can be given the Heart worksheet and asked to fill in the parts of the heart when discussed or the worksheet can be used as an assessment. Review the PowerPoint Presentation Cardiovascular Stents by Dr. Davis. When at the Create a Stent slide, tell students that they will create a stent using the items provided. Exploration Have the students work individually. 1. Have the students cut the Stent Example Template as instructed using x- acto knives or scissors. In either case, review safety procedures for handling these sharp items. 2. Take the cut paper and roll into a cylinder and tape the edges together as directed on the Stent Example Template. 3. When students have a stent created, place a balloon inside the stent and expand the balloon to demonstrate how the stent expands. Note: Several balloons can be partially inflated and tied. When needed, insert the partially inflated balloon into the stent and squeeze part of the balloon so that the balloon section inside the stent will expand. This process will eliminate the need to pump up a balloon for each student s stent, which is time consuming. Explanation Have the students describe their experiences of making their stent. As a class discuss the following questions: 1) What challenges might an engineer face when creating a similar technology for real arteries? Discuss the criteria and constraints for this engineering problem. Material selection is critical. The material must be strong to survive being inserted into the artery and threaded into the location of the blockage. However, it must also be flexible for placement at the blockage. The material must be biocompatible to not create an immune response or cause blood to clot. The stent must hold its shape after being expanded (both design and material selection important). The device must be small enough to fit into the artery. Also, the material cannot corrode over time while it is in place in the artery. Currently, bioabsorbable stents are being developed that will degrade in less than 12 months. Technical challenges require the materials and designs to balance mechanical properties, degradation time, and biocompatibility. A 2013 journal article (Lanzer, Strupp, Schmidt, Topoleski, 2013) cites that over

3 200 different stent types are available. The choice is made based on sizing, pricing, design, material, coating, drug loading, and mode of expansion. 2) What differences might there be between this setup and the actual artery and its location? The stent developed in class is much larger than an actual stent. The stent is made of paper, which would not be strong enough to move through an artery in blood. The method of testing the stent in class does not replicate the actual use of the stent as the stent is on a catheter that is inserted and threaded in the artery to the site of blockage. 3) What happens to the plaque after using a stent? The plaque is compressed against the arterial wall. 4) What would happen if only part of the blocked artery is cleared? o How might a partially blocked blood vessel affect a person's body? Full blood flow will not be restored. Also, if some of the plaque particles break free and flow downstream, they can cause additional blockage. 5) What additional complications could occur from use of a stent? Complications could include an allergic reaction to the contrast dye. This dye allows for the arteries to be seen on the X- ray. There could be a weakening of the artery wall caused by the procedure. As noted above, if plaque particles break free and flow downstream, additional blockage can occur. Bleeding at the catheter insertion site can occur. Approximately 1-2% of patients with a stent develop a blood clot at the location of the stent. If appropriate for the students, Poiseuille s Law can be introduced. Poiseuille s Law describes laminar flow of a Newtonian Fluid through a pipe. ΔP =!!"# (Equation 1)!!! where ΔP is the pressure difference across the pipe, μ is the viscosity of the fluid, L is the length of the pipe, Q is the volume flow rate, π is a mathematical constant equal to , and r is the radius of the pipe. Equation 1 can be written as ΔP = QR (Equation 2) where R is defined as the resistance to flow R =!!" (Equation 3)!!! The resistance to flow is inversely proportional to the fourth power of the radius, which means for a small decrease in radius, a much larger increase in the resistance to flow is observed. Therefore, when even a small amount of plaque is in an artery, the resistance to flow increases substantially. Rearranging Equation 2

4 Q =!! (Equation 4) shows that an increase in the resistance to flow decreases the volume flow rate of blood in the artery. Blood is actually a Non- Newtonian fluid, but Poiseuille s Law still can be used to provide a basic understanding of blood flow. Additional blood flow examples, can be found at: astr.gsu.edu/hbase/ppois2.html Elaboration Option 1: Provide the students with paper or graph paper. Individually, or with a partner, have students brainstorm different patterns for the stent and create the new stent. Allow the students to expand the stents with a balloon. Option 2: Have the students research the prevention or other medical treatments for heart disease and write a short report or presentation based on the research. Assessment Informal assessment is ongoing during the lesson. Be sure that the students are following lab safety procedures. Final assessment for Elaboration, Option 1: Have the students report their results of the second stent. They should discuss the success of the stent, any advantages or disadvantages, and further modifications that would improve the stent. Final assessment for Elaboration, Option 2 is the written report or presentation. Useful Resources Heart: Image of the heart of- the- heart; also has definitions of heart conditions, heart tests, and heart treatments Heart attacks: (select Heart Attack for a tutorial with animation of the heart. Specifically, see Heart Anatomy )

5 attack/ds00094 Stents: and- stenting.aspx Angioplasty and Stent Education Guide: Lanzer P, Strupp G, Schmidt W, Timmie Topoleski LD The need for stent- lesion matching to optimize outcomes of intracoronary stent implantation. J Biomed Mater Res Part B 2013: 101B: Poiseuille s Law: astr.gsu.edu/hbase/ppois2.html astr.gsu.edu/hbase/pturb.html Newtonian and non- Newtonian Fluids: newtonian.shtml Newtonian_fluid.html Viscosity: C_Research_Folder/Viscosity_def.html is- viscosity.htm Prerequisites The ability to follow written directions is required. Safety Be sure that students are using good lab safety practices. Remind students of proper handling of scissors and x- acto knives. Materials can be disposed in the trash. Alignment with Standards Next Generation Science Standards: MS- ETS1-1: Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit

6 possible solutions. Common Core State Standards: CCSS.ELA- Literacy.WHST.6-8.2a Introduce a topic clearly, previewing what is to follow; organize ideas, concepts, and information into broader categories as appropriate to achieving purpose; include formatting (e.g., headings), graphics (e.g., charts, tables), and multimedia when useful to aiding comprehension. CCSS.ELA- Literacy.WHST.6-8.2d Use precise language and domain- specific vocabulary to inform about or explain the topic. CCSS.ELA- Literacy.WHST Use technology, including the Internet, to produce and publish writing and present the relationships between information and ideas clearly and efficiently. CCSS.ELA- Literacy.RST Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks. CCSS.ELA- Literacy.RST Determine the meaning of symbols, key terms, and other domain- specific words and phrases as they are used in a specific scientific or technical context relevant to grades 6 8 texts and topics. CCSS.ELA- Literacy.WHST Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Worksheets Heart Worksheet for Students Heart Worksheet for Teachers Stent Example Template

Your heart is a muscular pump about the size of your fist, located

How Your Heart Works Your heart is a muscular pump about the size of your fist, located slightly to the left and behind your breastbone. Its function is to pump blood throughout your body. As your heart