The Tissue Industry &

History of Heart Valve Allografts

What does the tissue industry do?

The tissue industry procures, processes, stores and distributes allografts for life enhancing surgeries. When processed using the highest quality standards and adhering to strict policies and safety techniques, allograftsith the lack of regulations implemented and can substantially improve the quality of life for many patients. However, wenforced by FDA, this has created substantial problems within the industry and a number of tissue banks have been cited for using unsafe and inadequate tissue processing techniques. In light of these recent problems, it is important to discuss your concerns with your physician and identify which tissue processor will be providing your tissue. Once this is established it is important to research the company and their processes to be assured you are getting the highest quality and safest possible allograft.

What is an allograft?

An allograft is donated human tissue which is recovered from a cadaver. Bones, tendons, skin, heart valves, and corneas are the most widely used allografts.

How are allografts processed?

Most tissue is processed aseptically or using low dose irradiation. It is important to note when using an aseptic process, the outcome produces a non-sterile product.

Heart Valve Allografts;

Heart valve allografts sometimes called homografts, (homo meaning human) are valves which are harvested from cadaveric donors and in some instances from the explanted hearts of transplant recipients (1).

The most widely used heart valve allograft for replacement is the aortic valve. You may see the pulmonary valve allografts more widely used in children since the introduction of the Ross procedure. The Ross procedure involves the removal of the aortic valve and replaced with the patient's own pulmonary valve (autograft). The pulmonary valve is then replaced with an allograft.

Although some studies show the longevity and durability for human heart valve allografts may be a superior to that of heterografts (porcine or bovine) however, the mainstream use of allografts is still relatively in the early stages (15-20 years) so continued evaluation and research needs to be examined before a final determination and comparison can be made.

History of human heart valve allografts

The history of the heart valve allografts can be traced back to the 60's when the first fresh heart valve transplant in the cardiac position was performed by Sir Brian Barrat-Boyes of New Zealand and Donald Ross of London (2). After the initial introduction there was a flurry of excitement, however; the technology went virtually ignored by the cardiac surgical community except by a few notable exceptions (3).

Initially the allografts were harvested aseptically and implanted within a few days (4). Researchers continued to develop processing techniques which included the introduction of sterilizing the valves through the use of ethylene oxide or irradiation. Once sterilized, the valves would be stored in Hank's solution (saline solution) at 4 degrees C or the allograft would be freeze-dried. Unfortunately, this technique produced a high incidence of cusp rupture and degeneration.

Subsequently, antibiotics used for the decontamination of the allografts were then introduced in 1968 at Green Lane Hospital in New Zealand by Dr. Barratt-Boyes and followed by cryopreservation in 1975 by Dr. Mark O'Brien.

It was not until the past decade that human heart valve allografts have made a significant impact with a growing number of surgeons who have developed an appreciation for the valve qualities for use in pediatric, endocarditis cases and patients who are unable to undergo anticoagulant therapy.

Recent reports have suggested that cryopreserved heart valve allografts have well established advantages in avoiding anticoagulant therapy which is especially important for children and woman of child-bearing years; however, some researchers have claimed they have not found any significant difference in quality of life issues between mechanical valves and allografts (4).

Researchers have also reported findings of approximately 18.9% incidence of allograft failure within a mean interval of 5.4 years which is a matter of concern regarding the durability of these valves (4). These findings could suggest that allograft longevity is similar to that of porcine valves which have been reported to last up to 10-15 years.

Opinions among surgeons regarding the best valve for a patient remains allusive. There are many variables to be considered and examined for any patient considering heart valve replacement. Once again education is the key. A patient needs to examine their options very carefully and in concert with their physician decide the best possible solution given the individual patient's age, health, and quality of life issues.

References:

#1) Hunt, CJ. "Factors affecting the yield of cardiac valve allografts from living unrelated donors." European Journal Cardiothorac Surgery. 1998 Jan; 13(1): Pgs.71-77

#2) Baumgartner, N. "Microbiologic indicators as quality control in a valvular homograft bank." Transplantation Proceedings. 2001 Feb; 33(1-2): Pgs. 633-634

#3) Ross, DN. "Evolution of the homograft valve." Annals of Thoracic Surgery. 1995 Mar; 59(3): Pgs. 565-567.

#4) Ganguly Gautam, MS. "Homograft Aortic Valve Replacement- The Experience of One Unit." Heart, Lung and Circulation. 2004 June; 13(2): Pgs 161-167.


		The Tissue Industry & History of Heart Valve Allografts What does the tissue industry do? The tissue industry procures, processes, stores and distributes allografts for life enhancing surgeries. When processed using the highest quality standards and adhering to strict policies and safety techniques, allograftsith the lack of regulations implemented and can substantially improve the quality of life for many patients. However, wenforced by FDA, this has created substantial problems within the industry and a number of tissue banks have been cited for using unsafe and inadequate tissue processing techniques. In light of these recent problems, it is important to discuss your concerns with your physician and identify which tissue processor will be providing your tissue. Once this is established it is important to research the company and their processes to be assured you are getting the highest quality and safest possible allograft. What is an allograft? An allograft is donated human tissue which is recovered from a cadaver. Bones, tendons, skin, heart valves, and corneas are the most widely used allografts. How are allografts processed? Most tissue is processed aseptically or using low dose irradiation. It is important to note when using an aseptic process, the outcome produces a non-sterile product. Heart Valve Allografts; Heart valve allografts sometimes called homografts, (homo meaning human) are valves which are harvested from cadaveric donors and in some instances from the explanted hearts of transplant recipients (1). The most widely used heart valve allograft for replacement is the aortic valve. You may see the pulmonary valve allografts more widely used in children since the introduction of the Ross procedure. The Ross procedure involves the removal of the aortic valve and replaced with the patient's own pulmonary valve (autograft). The pulmonary valve is then replaced with an allograft. Although some studies show the longevity and durability for human heart valve allografts may be a superior to that of heterografts (porcine or bovine) however, the mainstream use of allografts is still relatively in the early stages (15-20 years) so continued evaluation and research needs to be examined before a final determination and comparison can be made. History of human heart valve allografts The history of the heart valve allografts can be traced back to the 60's when the first fresh heart valve transplant in the cardiac position was performed by Sir Brian Barrat-Boyes of New Zealand and Donald Ross of London (2). After the initial introduction there was a flurry of excitement, however; the technology went virtually ignored by the cardiac surgical community except by a few notable exceptions (3). Initially the allografts were harvested aseptically and implanted within a few days (4). Researchers continued to develop processing techniques which included the introduction of sterilizing the valves through the use of ethylene oxide or irradiation. Once sterilized, the valves would be stored in Hank's solution (saline solution) at 4 degrees C or the allograft would be freeze-dried. Unfortunately, this technique produced a high incidence of cusp rupture and degeneration. Subsequently, antibiotics used for the decontamination of the allografts were then introduced in 1968 at Green Lane Hospital in New Zealand by Dr. Barratt-Boyes and followed by cryopreservation in 1975 by Dr. Mark O'Brien. It was not until the past decade that human heart valve allografts have made a significant impact with a growing number of surgeons who have developed an appreciation for the valve qualities for use in pediatric, endocarditis cases and patients who are unable to undergo anticoagulant therapy. Recent reports have suggested that cryopreserved heart valve allografts have well established advantages in avoiding anticoagulant therapy which is especially important for children and woman of child-bearing years; however, some researchers have claimed they have not found any significant difference in quality of life issues between mechanical valves and allografts (4). Researchers have also reported findings of approximately 18.9% incidence of allograft failure within a mean interval of 5.4 years which is a matter of concern regarding the durability of these valves (4). These findings could suggest that allograft longevity is similar to that of porcine valves which have been reported to last up to 10-15 years. Opinions among surgeons regarding the best valve for a patient remains allusive. There are many variables to be considered and examined for any patient considering heart valve replacement. Once again education is the key. A patient needs to examine their options very carefully and in concert with their physician decide the best possible solution given the individual patient's age, health, and quality of life issues. References: #1) Hunt, CJ. "Factors affecting the yield of cardiac valve allografts from living unrelated donors." European Journal Cardiothorac Surgery. 1998 Jan; 13(1): Pgs.71-77 #2) Baumgartner, N. "Microbiologic indicators as quality control in a valvular homograft bank." Transplantation Proceedings. 2001 Feb; 33(1-2): Pgs. 633-634 #3) Ross, DN. "Evolution of the homograft valve." Annals of Thoracic Surgery. 1995 Mar; 59(3): Pgs. 565-567. #4) Ganguly Gautam, MS. "Homograft Aortic Valve Replacement- The Experience of One Unit." Heart, Lung and Circulation. 2004 June; 13(2): Pgs 161-167.