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Jack Bokros

A lifetime of commitment to improving patient care means heart valves…designed for life.

jack bokros2 181x300 Jack Bokros

Jack Bokros PhD is the recipient of the Surfaces in Biomaterials Foundations’ Lifetime Achievement Award for Excellence in Surface Science. The award was granted for the development of isotropic pyrolytic carbon that he discovered in 1963 while working on the General Atomic Company’s project to utilize nuclear fuel to generate electrical power.1,2 In 1965, Dr. Bokros redirected his focus from power generation to potential medical applications for the new carbon material.

After 40 years of striving for better design and production methods with pyrolytic carbon for heart valve implants, Dr. Bokros and his team have revolutioned mechanical valve capabilities with the On-X® Prosthetic Heart Valve—designed for life!3-23

The unique design of the On-X valve and improved clinical outcomes convinced the FDA to approve the first ever reduced anticoagulation clinical trial, PROACT.24

jack bokros figure13 Jack Bokros

Not all carbons are the same…
a tale of two carbons*…

jack bokros figure21 Jack Bokros

Scanning electron micrography compares the surface of pure On-X® carbon with that of original pyrolytic carbon that is co-deposited with silicon carbide used in earlier generation valves.23 An improvement in the control of the process produced a quantum leap in carbon technology that lead to a superior material that allows smooth contouring of the pivot, eliminates sharp corners, crevices and grinding flaws, and sets an unsurpassed standard for surface quality.18

The superior mechanical properties of On-X carbon made it possible to produce an orifice design for a new valve that organizes flow and eliminates turbulence mimicking the hemodynamics of the natural valve.19-20 The new On-X valve is the first prosthetic heart valve on the market to produce mean gradients under 10mmHg in every size.25,26

The On-X actuated pivot is designed to allow the leaflets to follow the flow to open to 90° thus reducing downstream turbulence.22 A closing ramp in the pivot area insures that the leaflets will close when the blood flow reverses. Closing contact points are configured to soften the closure impact and noise. On-X patients, implanting surgeons and cardiologists report little noise from the On-X valve.27

The pivot incorporates flow channels that provide a complete “purge” when the valve leaflets are closed avoiding stasis–this may be one factor that contributes to remarkably low thrombotic rates for the On-X valve.25-32

Evidence of lowered turbulence…

jack bokros figure3 Jack Bokros

Comparative echocardiography shows laminar flow that is characteristic of the On-X valve (solid red and blue) and turbulent flow characteristic to first generation bileaflet valves (mosaic of colors).33 Minimizing turbulent flow improves coronary flow.34

Lactate dehydrogenase (LDH) levels are within the normal ranges for the On-X valve, unlike its predecessors.35-37 The On-X valve performs like a tissue valve in this respect.

Proven clinical performance led to the first and only lowered anticoagulation study approved by the FDA, PROACT.24

    Clinical proof that lowered anticoagulation would be feasible:

  • Study data generated for market approval by the FDA in the United States compared to data for other valves showed a 50-60% reduction of morbid event rates.25,38-39
  • A South African study of On-X valves showed a very reduced thrombosis rate in a non-compliant population compared to earlier generation valves.28
  • An aspirin-only study of the On-X valve in Germany produced no significant differences in morbid event rates between the aspirin-only group and standard warfarin therapy group.40
  • Tests of On-X and other bileaflet valves in a sheep model showed significantly higher thromboresistance for the On-X valve.41,42

      • The Prospective Randomized On-X Valve Anticoagulation Clinical Trial (PROACT), approved by the FDA for 40 centers in the USA, was initiated in June of 2006.24

      PROACT Study Drug Therapy Groups
      Low risk aortic patients: clopidogrel plus aspirin (81mg/day)
      High risk aortic patients: INR of 1.5-2.0 plus aspirin (81mg/day)
      Mitral patients: INR of 2.0-2.5 plus aspirin (81mg/day)
      Control groups: AHA/ACC standards

      The lead center for PROACT is Emory University in Atlanta, Georgia USA.

      One Scientist’s Quest for the Ideal Heart Valve Replacement . . . One Valve for Life

      1963 – Discovery of isotropic15 pyrolytic carbon

      1965 – Collaboration of Dr. Gott and Dr. Bokros to evaluate potential blood contact materials confirms isotropic pyrolytic carbon has favorable properties—it is thromboresistant, durable and biostable.3-13

      1968 – The first pyrolytic carbon heart valve component is produced at General Atomic Company (GAC) for the DeBakey aortic heart valve and implanted in 1968.

      1972 – GAC produces the first carbon disk occluders to replace metallic and polymeric components. Pyrolite Carbon becomes the preferred material for occluders.11

      1976 – St. Jude Medical, Inc., (SJM) approached GAC in 1976 to develop an all carbon heart valve replacement. The carbon components for the first SJM valve implanted were produced in 1977.

      1979 – Dr. Bokros formed CarboMedics (CMI) in Austin, Texas. Pyrolytic carbon components are produced for SJM, Duromedics-Edwards, Bjork-Shiley, Omniscience-Omnicarbon, Medtronic Hall, Bicer and other valves.

      1985 – Dr. Bokros files patents that cover two pivot designs. One has been employed in the original CarboMedics valve.14 The other was licensed for use in the ATS Medical, Inc., valve.15

      1989 – Carbon Implants, Inc. (Cii) is formed to improve carbon-processing technology. A major advance in control of the pyrolytic process expands the potential of the process.16

      1989 – Dr. Bokros envisions the potential of the new carbon and the possibility for use in a generational advance in heart valve replacement.

      1994 – Medical Carbon Research Institute (MCRI) and the new carbon is named On-X® carbon. With the wisdom and experience of the MCRI team, Dr. Bokros designs the On-X® Prosthetic Heart Valve focusing primarily on the elimination of stasis and turbulence leading to reduction of blood trauma and clotting.

      1996 – The first implant of the On-X valve.

      2001 – FDA approval of the On-X valve is granted.25

      2006 – FDA approves first ever reduced anticoagulation study, PROACT.24

      References

      1. Bokros JC. Random pyrolytic carbon. Nature 1964;202(4936):1004-05
      2. Bokros JC, Price RJ, Trozera TA. Influence of structure on mechanical properties of pyrolytic carbon. Nature 1964;204(4956)371-72
      3. LaGrange LD, Gott VL, Bokros JC, et al. Compatibility of carbon and blood. Artificial Heart Program Conference Proceedings, (Ruth Johnson Hegyeli, ed.) NIH, Washington DC 1964; Chapter 5:47
      4. Bokros JC, Gott VL, LaGrange LD, et al. Correlations between blood compatibility and heparin adsorptivity for an impermeable isotropic pyrolytic carbon. J Biomed Mater Res 1969;3:497
      5. Bokros JC, Gott VL, LaGrange LD, et al. Heparin sorptivity and blood compatibility of carbon surfaces. J Biomed Mater Res 1970;4:145
      6. Bokros JC, LaGrange LD, Schoen FJ. Control of structure of carbon for use in bioengineering. Chemistry and Physics of Carbon. (PL Walker Jr., ed.) Marcel Dekker, Inc., New York. 1972;9:103
      7. Bokros JC, Akins RJ, Shim HS, et al. Prostheses made of carbon. Chemical Technology 1977;7:40
      8. Bokros JC, Akins RJ. Applications of pyrolytic carbon in artificial heart valves in Opportunities in Materials (MC Shaw, ed.) Proceedings of the Fourth Buhl International Conference on Materials, Carnegie Press, Carnegie-Mellon University, Pittsburgh PA USA 1971;243
      9. Bokros JC, Akins RJ, Shim HS, et al. Carbon in prosthetic devices in Petroleum Derived Carbons, ACS Symposium Series 21 (ML Deviney and TM O’Grady, eds.) American Chemical Society 1975;237
      10. Bokros JC. Deposition, structure and properties of pyrolytic carbon in Chemistry and Physics of Carbon (PL Walker, ed.) Marcel Dekker, Inc. New York 1969;5:1
      11. Bokros JC. Carbon in medical devices. Carbon 1977;15:355
      12. Ma L, Sines GH. Fatigue behavior of a pyrolytic carbon. J Biomed Material Res 2000;51:61-68
      13. Ma L, Sines GH. Unalloyed pyrolytic carbon for implanted mechanical heart valves. J Heart Valve Dis 1999;8:578-85
      14. Bokros JC. US Patent No. 4,689,045. August 25, 1987
      15. Bokros JC. US Patient No. 4,692,165. September 8, 1987
      16. Accuntius J, Wilde D. Deposition of pyrolytic carbon in fluid bed. US Patent No. 5,284,676. February 8, 1994
      17. Ely J, Emken M, Accuntius J, et al. Pure pyrolytic carbon; preparation and properties of a new material, On-X carbon, for mechanical heart valve prostheses. J Heart Valve Dis 1998;7:626-32
      18. Ely JL, Haubold AD, Emken MR, et al. Pyrocarbon and process for depositing pyrocarbon coatings. US Patent No. 5,514,410. May 7, 1996 and US Patent No. 5,677,061. October 14, 1997
      19. Bokros JC, Emken MR, Haubold AD, et al. Prosthetic heart valve. US Patent No. 5,677,061. May 3, 1994 and US Patent No. 5,137,532. August 11, 1992
      20. Bokros JC, Ely JL, Emken MR, et al. Prosthetic heart valves with improved blood flow. US Patent No. 5,772,694. August 11, 1992
      21. Bokros JC, Ely JL, Emken MR, et al. Prosthetic heart valve. US Patent No. 5,642,324. June 24, 1997
      22. Bokros JC, Stupka JC, More RB, et al. Prosthetic heart valve. US Patent No. 6.096,075. August 1, 1993
      23. Kaae JL, Ely JL, Schwartz AS. Microstructural observations of pure pyrolytic carbons for heart valves. Twenty-second Biennial Conference on Carbon. J Transaction 1995;742-43
      24. PROACT Investigation Plan.On-X Life Technologies, Inc.™, Austin, Texas USA; © 2006
      25. Summary of Safety and Effectiveness, On-X® Prosthetic Heart Valve, FDA PMA P000037 and P000037/S1, May 30, 2001 and March 6, 2002. European Primary Trial, updated May 31, 2003
      26. Instructions for Use, On-X® Prosthetic Heart Valves, On-X Life Technologies, Inc.™;
      27. Internal communication, On-X Life Technologies, Inc.™; 2007
      28. Williams MA, van Riet S. The On-X® Prosthetic Heart Valve: Mid-term results in a poorly anticoagulated population. J Heart Valve Dis 2006;15:80-86
      29. Palatianos GM, Laczkovics AM, Simon P, et al. Multicentered European study on safety and effectiveness of the On-X Prosthetic Heart Valve: Intermediate follow-up. Ann Thorac Surg 2007;83:40–6
      30. Ozurda U, Akar AR, Uymaz O, et al. Early clinical experience with the On-X Prosthetic Heart Valve. Interactive Cardiovasc Thorac Surg 2006; doi:10.1510/icvts.2005.114843: 7
      31. McNicholas KW, Ivey TD, Metras J, et al. The North American multi-center experience with the On-X® Prosthetic Heart Valve. J Heart Valve Dis 2006;15:73-79
      32. Tsai HW, Hsieh SR, Ji H, et al. Seven-year experience with On-X® Prosthetic Heart Valves in an Asian population with high risk cardiac status and reduced anticoagulation. Poster 146 presentation at the Fourth Biennial Meeting of the Society of Heart Valve Disease. New York, June 2007
      33. Mahajan A. Cardiovascular Anesthesia Program, University of California at Los Angeles Medical Center, private communication 2006.
      34. Bakhtiary F, Schiemann M, Dzemali O, et al. Impact of patient-prosthesis mismatch and aortic valve design on coronary flow reserve after aortic valve replacement. J Am Coll Cardiol, 2007; 49:790-796
      35. Birnbaum D, Laczkovics A, Heidt M, et al. Examination of hemolytic potential with the On-X® Prosthetic Heart Valve. J Heart Valve Dis 2000;9:142-45
      36. Mecozzi G, Milano AD, De Carlo M, et al. Intravascular hemolysis in patients with new-generation prosthetic heart valves: a prospective study. J Thorac Cardiovasc Surg 2002;123:550-56
      37. Skoularigis J, Essop MR, Skudicky D, et al. Frequency and severity of intravascular hemolysis after left-sided cardiac valve replacement with Medtronic Hall and St. Jude Medical prostheses, and influence of prosthetic type, position, size and number. Am J Cardiol 1993;71:587-91
      38. Kortke H, Korfer R. International normalized ratio self-management of a mechanical heart valve replacement: is an early start advantageous? Ann Thorac Surg 2001;71:44-48
      39. Comparison of On-X morbid event rates with those of St. Jude, Carbomedics and Medtronic-Hall prostheses reported in On-X Experience, 2001;3(2) published by On-X® Life Technologies, Inc., Austin, Texas
      40. Laczkovics AM. Lower anticoagulation trials for mechanical heart valves. Abstract presented the Japanese Society of Cardiovascular Surgeons; Morioka City, Japan; April 12 – 14, 2006
      41. Flameng W, Meuris B. Performance of bileaflet heart valve prostheses in an animal model of heart valve thrombosis. 6th Annual Hilton Head Workshop on Prosthetic Heart Valves, March 6-10, 2002, Hilton Head, South Carolina
      42. Meuris B, Flameng W. Performance of the On-X bileaflet mechanical valve in a chronic sheep model of mechanical valve thrombosis. Innovations in Cardiac Surgery 2003. Symposium in conjunction with annual AATS meeting May 3, 2003, Boston, Massachusetts, p. 26

      CAUTION: Federal law restricts this device to sale by or on the order of a physician. Refer to the instructions for use that accompany each valve for indications, contraindications, warnings, precautions and possible complications. CAUTION: This investigational use of this device is limited by Federal law to investigational sites.

      Headquarters and Manufacturing Facilities:
      1300 East Anderson Lane, Building B Austin, Texas 78752 U.S.A. – Telephone: (512) 339-8000 – Facsimile: (512) 339-3636 – www.onxlti.com – onx@onxlti.com
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