Page 2 - Week 2

April 8, 2015

This week, the main task was to gather research. We focused mainly on the blood pressure, different heart valve issues, and current valve designs. Knowing the blood pressure is important because it dictates the pressure gradient needed to open and close the valve. The heart pumps with about 1.8 psi and it contracts with about 1.4 psi. Because of this, the valve has to be open and close with at least 1.4 psi. Not all hearts pump with the same pressure, so a stiffness adjustment could be added. With this, the doctor could measure blood pressure of the patient and adjust the valve according to the patient's needs.

There were a few main heart valve issues, that include regurgitation and stenosis. In regurgitation, the valve does not completely close, allowing for backwards flow. Stenosis, on the other hand, The valve's opening becomes narrowed or does not form properly, which then forces the heart to pump harder. Another huge issue with heart valves is that replacements can lead to blood clotting around the new valve. To accommodate this, patients have to take blood thinners or can face an embolism. The final issue that we came across today is the lifespan of a valve. We wanted to use a material, one similar to polyurethane so prevent clotting, but we were unsure if that would be as reliable as a metal one.

The last main component that was researched was current heart valves. Many of the current valves are made out of polyurethane, which is where we got the idea to use that as our material. The most popular design is a three-leaf design. The leaves mimic a real heart valve and open up when blood goes through them. When the blood stops flowing through, it creates an airtight seal with the other leaves to prevent any backwards flow.

 

Figure 1: A 3-leaf heart valve [4]

Below are two videos of a doctor explaining the Heart Valve Replacement process. It's essential that one understands the fundamentals of this intense surgery and the reason behind why surgeries like this need to take place. Doing research like this will in addition enable us to understand and think of ways to better create a new and different artificial heart valve. 

 

From these videos, we learned that:

• the heart is composed of four main components:
• Right and Left Atria & Right and Left Ventricles
•  Has to have one-way valves to prevent ‘sloshing’
• Allows blood in, but then prevents it from going outward
• Tricuspid valve
• Purpose: to make sure blood is circulating and flowing in only ONE direction
• works by changes of pressures in the heart
• Pressure in left pump is 5x the pressure in the right pump
• Common problems
• People born with floppy or stretched out mitral valve à mitral valve prolapse à leak
• Gradual narrowing of aortic valve à aortic stenosis
• Traditional heart valves
• Tissue valve
• Made the way we are made – out of human tissue
• Mechanical heart valve
• Requires medicine to be taken along with it
• 
  

Example Tissue Artificial Heart Valve [14]

Example Mechanical Heart Valve [8]

Sources:

[1] Gwheartandvascular.org, '» Anatomy and Function of the Heart Valves', 2015. [Online]. Available: http://www.gwheartandvascular.org/education/anatomy-and-function-of-the-heart-valves/. [Accessed: 22- Apr- 2015].

[2] Ffcars.com, 'What's Blood Pressure in PSI??? - FFCars.com : Factory Five Racing Discussion Forum', 2015. [Online]. Available: http://www.ffcars.com/forums/43-off-topic-discussions/90855-whats-blood-pressure-psi.html. [Accessed: 22- Apr- 2015].

[3] Sciencedirect.com, 'New polyurethane heart valve prosthesis: design, manufacture and evaluation', 2015. [Online]. Available: http://www.sciencedirect.com/science/article/pii/0142961295002421. [Accessed: 22- Apr- 2015].

[4] Heart.org, 'Types of Replacement Heart Valves', 2015. [Online]. Available: http://www.heart.org/HEARTORG/Conditions/More/HeartValveProblemsandDisease/Types-of-Replacement-Heart-Valves_UCM_451175_Article.jsp. [Accessed: 22- Apr- 2015].

[5] YouTube, 'Heart Valve Replacement Surgery Explained Part 2', 2015. [Online]. Available: https://www.youtube.com/watch?v=YyJhvC4oCHQ&spfreload=1. [Accessed: 22- Apr- 2015].

[6] YouTube, 'Heart Valve Replacement Surgery Explained Part 1', 2015. [Online]. Available: https://www.youtube.com/watch?v=E0RD6-foBKQ. [Accessed: 22- Apr- 2015].

[7] Clemson.edu, 2015. [Online]. Available: http://www.clemson.edu/glimpse/wp-content/uploads/2013/03/heart-valve-picture-1.jpg. [Accessed: 22- Apr- 2015].

[8]Mechanical Heart Valve. 2015.

[9] Gwheartandvascular.org, '» Anatomy and Function of the Heart Valves', 2015. [Online]. Available: http://www.gwheartandvascular.org/education/anatomy-and-function-of-the-heart-valves/. [Accessed: 22- Apr- 2015].

[10] Ffcars.com, 'What's Blood Pressure in PSI??? - FFCars.com : Factory Five Racing Discussion Forum', 2015. [Online]. Available: http://www.ffcars.com/forums/43-off-topic-discussions/90855-whats-blood-pressure-psi.html. [Accessed: 22- Apr- 2015].

[11] Sciencedirect.com, 'New polyurethane heart valve prosthesis: design, manufacture and evaluation', 2015. [Online]. Available: http://www.sciencedirect.com/science/article/pii/0142961295002421. [Accessed: 22- Apr- 2015].

[12] Heart.org, 'Types of Replacement Heart Valves', 2015. [Online]. Available: http://www.heart.org/HEARTORG/Conditions/More/HeartValveProblemsandDisease/Types-of-Replacement-Heart-Valves_UCM_451175_Article.jsp. [Accessed: 22- Apr- 2015].

[13] Clemson.edu, 2015. [Online]. Available: http://www.clemson.edu/glimpse/wp-content/uploads/2013/03/heart-valve-picture-1.jpg. [Accessed: 22- Apr- 2015].

[14] A bioprosthetic heart valve has been fabricated from a pig’s valve using the new cross-linking method developed in Vyavahare’s lab. Image credit courtesy of the Naren Vyavahare lab.. 2015.