BIOMATERIALS ENT 219

1. BIOMATERIALSENT 219 Blood Contacting Implants or Devices Prepared by: Nur Farahiyah Binti Mohammad

2. 1.0 Introduction • Blood contacting implants or devices have a direct contact with the blood. • Blood comes in contact with foreign materials either for a short term or long term. • 2types blood contacting implant

3. 1.0 Introduction Short term extracorporeal devices (outside the body) Blood Oxygenator Tubes and catheters Dialyzer

4. 1.0 Introduction Heart valve prosthesis Cardiac Pacemakers

5. 1.0 Introduction Total Artificial Heart Artificial Vascular Graft

6. 2.0 Primary requirement • The primary requirement for biomaterials for long-term implants are: • Blood compatibility (blood compatible) • Non-toxicity • Durability • Non-irritating to tissue • Resistant to platelet and thrombus deposition • Nondegradable in physiological enviroment • Do not absorb blood element • Do not release foreign substance

7. 3.0 Design consideration • The implant should mimic the function of organ that it replace without interfering with the surrounding anatomical structures. • Must be suitable size and weight

8. 3.0 Design consideration • Biomaterial chosen must be; • easily available, • inexpensive, • Easy to fabricate • sterilizable.

9. 3.0 Design consideration • As an example: • artificial heart valve is required to open and close on an average once every second (valves open and close 30 million times per year). • The biomaterial chosen must be such that the valve is durable and will not fail under fatigue stress after implantation in patient.

10. Revision “ Biocompatibility is the ability of a material to perform with an appropriate host response in a specific application” (William, 1987).

11. Revision • In vivo test for tissue compatibility • Sensitization • Irritation • Intracutaneous reactivity • Systemic toxicity (acute toxicity) • Subcronic toxicity (subacute toxicity) • Genotoxicity • Implantation • Hemocompatibility (Blood compatibility)

12. 4.0 Blood compatibility • Blood compatibility can be defined as the property of material or device that permits it to function in contact with blood without inducing adverse reactions. • Implant should not • Induce coagulation (blood clotting) • Damage blood cells • Should not induce Hemolysis (the breaking open of red blood cells and the release of hemoglobin into the surrounding fluid)

13. 4.0 Blood compatibility 4.1Blood Coagulation • Coagulation is a complex process by which blood forms clots. 4.1.1 Mechanism: • Intrinsic • Initiated by blood contact with either a damaged portion of the blood vessel wall or another thrombogenic (clot causing) surface. • Takes 7-12 minutes to form a soft clot

14. 4.0 Blood compatibility • Extrinsic • Result of the presence of a foreign body or tissue damage (other than blood vessel) • Takes 5-12 seconds to form a soft clot

15. 4.0 Blood compatibility 4.1.2 Factor affect the blood compatibility of a material • Surface roughness • Rough surface have a greater surface area and contact surface with blood compared to smooth surfaces • Result in faster coagulation

16. 4.0 Blood compatibility • Surface Charge • The tunica intima (the innermost layer of artery or vein) of a normal blood vessel has a negative surface charge due to proteins at surface of the cell membrane. • Formed blood element (red cells, white cells, and platelets) also have a negative charge. • Natural repulsive force between intima and cells minimizes cell damage and coagulation • Low surface tension • Blood cells less likely to adhere to a surface with a low surface tension

17. 4.0 Blood compatibility • Heparinized surfaces • Heparin is a polysaccharide with negative charge. • Heparin is a naturally-occurring anticoagulant produced by basophils and mast cells. • Heparin acts as an anticoagulant, preventing the formation of clots and extension of existing clots within the blood. • it allows the body's natural clot lysis mechanisms to work normally to break down clots that have already formed • Attempt made to attach heparin chemically to the surface of the implant to prevent blood clot.

18. 4.0 Blood compatibility 4.2 HEMOLYSIS • Motion at a blood-surface interface may damage red and white blood cell resulting in cell death. • Damage of cell occurs with shear stresses on the cells of less than 500dyn/cm2 . • Chronic and accumulated damage of red blood cells and leakage of the cellular contents can result in: • Anemia • Kidney Failure • Toxemia

19. Blood contacting implant or devices

20. 5.0 Heart valve prostheses HEART VALVES • Heart valves are very important, as they prevent the backflow of blood, which ensures the proper direction of blood flow through the circulatory system. • Without these valves, the heart would have to work much harder to push blood into adjacent chambers. The heart is composed of 4 valves: tricuspid, pulmonary, mitral, and aortic.

21. 5.0 Heart valve prostheses HEART VALVE PROBLEMS • There are numerous complications and diseases of the heart valves that prevent the proper flow of blood. • Heart valve diseases fall into two categories, • Stenosis • The stenotic heart valve prevents the valve from opening fully, due to stiffened valve tissue. Hence, there is more work required to push blood through the valve • Incompetence. • the incompetent valves cause inefficient blood circulation by permitting backflow of blood in the heart

22. Stenosis Incompetence

23. 5.0 Heart valve prostheses TREATMENT OPTIONS • On a large scale, medication is the best alternative, although in some cases defective valves have to be replaced with a prosthetic valve in order for the patient to live a normal life.

24. 5.0 Heart valve prostheses MAIN PROSTHETIC HEART VALVE • Heart valve prostheses can be classified into two type: • Mechanical prostheses : made of non-biological materials. • Biological heart valve: made of biological tissue • Heart valves are designed to fit the peculiar requirements of blood flow through the specific chambers of the heart, with emphasis on producing more central flow and reducing blood clots.

25. MECHANICAL PROSTHESIS Caged ball This valve uses a small ball that is held in place by a welded metal cage. The ball in cage design was modeled after ball valves used in industry to limit the flow of fluids to a single direction 5.0 Heart valve prostheses

26. 5.0 Heart valve prostheses • Tilting disc • Have a polymer disc held in place by two welded strut • The disc floats between the two struts in such a way, as to close when the blood begin to travel backward and then reopen when blood begin to travel again. • The titling-disc valves open at an angle of 60° and close shut at rate of 70 times/minute

27. 5.0 Heart valve prostheses • Advantages: • Provide improved central flow while still preventing backflow • Reduce mechanical damage to blood cells • Reduce blood clotting and infection • Problem: • Have a tendency for the outlet strut to fracture as a result of fatigue from the repeated ramming (smash into) of the struts by the disc.

28. 5.0 Heart valve prostheses • Bileaflet valves • Consist of two semicircular leaflets that pivot on hinges • Advantages: • Provide the closest approximation to centarl flow achieved in natural heart valve. • Disadvantages: • They do not close completely, which allows some backflow. • Since backflow is one of the properties of defective valves, the bileaflet valves are still not ideal valves.

29. 5.0 Heart valve prostheses • Trileaflet heart valve • Afford true central flow characteristic with reduced back flow • Good wear characteristic. • Significantly improve patient’s quality of life. • This will be achieved due to reduced consumption of anticoagulants by the patients, reduced noise, low blood hemolysis, and the elimination of the need for repeated implantations because of high reliability of the mechanical design.

30. 5.0 Heart valve prostheses • BIOMATERIAL USED IN MECHANICAL HEART VALVE

31. 5.0 Heart valve prostheses

32. 5.0 Heart valve prostheses

33. 5.0 Heart valve prostheses • BIOLOGICAL/ PROSTHETIC TISSUE HEART VALVE • Human tissue valves • Animal tissue valve Advantages: • Design of valve are closer to the design of the natural valve. • Do not require long term anticoagulant • Do not cause damage to blood cells • Do not suffer from many of structural problems experienced by the mechanical heart valve

34. Human Tissue valve • Homograft: valves that are transplanted from another human being • Autograft: valves that are transplanted from one position to another within the same person. • Dysfunctional aortic valve (exit of the left ventricle) is removed, patient’s pulmonic valve is then transplanted to the aortic position. • A homograft pulmonic valve is usually used to replace the patient’s pulmonic valve.

35. Human Tissue valve

36. Animal tissue valve • Refereed as heterograft or xenograft valves. • The two common prosthesis valve from animal tissue are: • PORCINE VALVES • BOVINE PERICARDIAL VALVE

37. Animal tissue valve • PORCINE VALVES • Valve tissue from pig • Valve tissue is sewn to a metal wire stent made of cobalt-nickel alloy. • The wire is bent to form three U-shaped prongs. • A Dacron cloth sewing skirt is attached to the base of the wire stent, and then the stents themselves are also covered with cloth. • Porcine valves have good durability and usually last for ten to fifteen years.

38. Animal tissue valve • BOVINE PERICARDIAL VALVE • Bovine pericardial valves are similar to porcine valves in design. • The major difference is the location of the small metal cylinder which joins the ends of the wire stents together. • In the case of pericardial valves, the metal cylinder is located in the middle of one of the stent post loops. • Pericardial valves have excellent hemodynamics and have durability equal to that of standard porcine valves after 10 years.

39. Porcine valve Leafleat Stent

40. Pericardial valve Leafleat Stent Suture ring

41. Biological tissue valves

42. Biological tissue valves

43. Common problem with implanted heart valve

44. Prosthetic heart valve type

45. Conclusion HV • The future for replacement heart valves lies in tissue engineering. • The most ideal replacement would be formed from the patient's tissue, and tailored to the right shape and dimensions. • This would improve the biocompatibily factor, and increase the life expectancy of the heart valve.

46. 6.0 VASCULAR GRAFT BLOOD VESSELS • Blood vessel are the channels through which blood is distributed to body tissue. • Blood vessel are classified as either: • Arteries (carry blood away from the heart) • Capillaries • Veins (carry blood to the heart)

47. 6.0 VASCULAR GRAFT BLOOD VESSELS PROBLEMS • Vascular graft is needed to replace diseased blood vessel such as atherosclerosis blood vessel and aortic aneurysm . • Atherosclerosis is a disease in which plaque (plak) builds up on the insides of your arteries.   • Aneurysm is blood-filled dilation (balloon-like bulge) of a blood vessel caused by disease or weakening of the vessel wall.

48. Blood vessel problem Aneurysm Atherosclerosis

49. 6.0 VASCULAR GRAFT TREATMENT OPTIONS • The main treatment for atherosclerosis is lifestyle changes. You also may need medicines and medical procedures. • For aortic aneurysms or aneurysms that happen in the vessels that supply blood to the arms, legs, and head (the peripheral vessels), surgery involves replacing the weakened section of the vessel with an artificial tube.

50. 6.0 VASCULAR GRAFT