Social Responsibility and Professional Ethics in Engineering Assignment | B.Tech 6th Sem, ECEcentercenterELB15028-ELB15040
Pfizer Bjork-Shiley heart valve case
We are really grateful because we managed to complete our SRPEE assignment on “PFIZER BJORK-SHILEY HEART VALVE CASE” within the time given by our lecturer Mrs. Kakoli Mahanta. This assignment cannot be completed without the effort and co-operation of our group members (ELB15028-40).
We would like to sincerely thank our subject teacher Mrs. Kakoli Mahanta, who has given us the opportunity to do the assignment and also for the guidance in completion of the assignment . Last but not the least , we would like to express our gratitude to our friends for spending some time with us in helping with our assignment.SUBMITTED BY
SL. NAME ROLL NO.
1 Amlanjyoti Das ELB15028
2 Bishal Kenari ELB15029
3 Pranami Sonowal ELB15030
4 Harshit Kr. Borah ELB15031
5 Bikash Deka ELB15033
6 Juman Hazarika ELB15034
7 Pranjal Das ELB15035
8 Tanaya Das ELB15036
9 Pulagam Sujith Kumar ELB15037
10 Rakesh Kr. Ray ELB15039
11 Suraj ELB15040
1. INTRODUCTION 5
1.1 BACKGROUND 6
1.2 VALVULAR DISEASES 6
2. THE BJORK-SHILEY VALVE 6
2.1 CONSTRUCTION 7
2.2 WORKING 7
2.3 DEVICE FAILURE 7
2.4 FAILURE SYMPTOMS 8
3. CAUSES OF FAILURE OF B.S. HEART VALVE FROM THREE BASIC PERSPECTIVE 8
4. RECALL 9
4.1 RECALL FACTORS 9
4.2 RISK FACTORS FOR OUTLET STRUT FAILURE (OSF) 9
4.3 ISSUES INVOLVED IN APPLYING GUIDELINES TO INDIVIDUAL PATIENTS 12
5. DECEIT AND DECEPTION 12
5.1. ACTIVITIES OF THE SUPERVISORY PANEL ESTABLISHMENT SURGERY 13
6. ETHICAL ISSUES THAT AROSE AS A RESULT OF THE PROBLEM AND RECALL 14
7. ETHICAL DILEMMAS 15
8. CONCLUSION 16
9. BIBLOGRAPHY 17
The past half century has witnessed enormous advances in the development and refinement of implantable medical devices such as heart valves, joint replacements, and pacemakers/defibrillators. For the most part, these devices have improved the quality and, in some cases, the duration of human life. Unfortunately, occasional unexpected adverse events have and will continue to occur (e.g., the recently reported problems with hip replacements and cardiac pacemaker/ defibrillator leads), with the result that very careful monitoring of new devices is now recognized to be an essential component of the evaluation of health services and the protection of patients. Fracture of the outlet strut of the Björk-Shiley convexo-concave (BSCC) heart valve was one of the first and most catastrophic of these adverse events.
The B.S. valve, originally released in 1978,was approved by the Food and Drug Administration (FDA) in 1979, after which large numbers were distributed by Pfizer Inc., for implantation worldwide. During the next several years, multiple instances of catastrophic failure of the B.S. valve, often with patient death, were reported These reports resulted in numerous wrongful death lawsuits.
The heart has four valves: the aortic valve and the mitral valve on the left side; the pulmonary valve and the tricuspid valve on the right side.
1.2 VALVULAR DISEASES
The valvular disease usually involves two conditions: valvular stenosis and valvular insufficiency. Valvular stenosis occurs when a valve opening issmaller than normal due to stiff or fused leaflets. The narrowed opening may make the heart work very hard to pump blood through it. This can lead to heart failure. All four valves can be stenotic (hardened, restricting blood flow); the conditions are called tricuspid stenosis, pulmonic stenosis, mitral stenosis or aortic stenosis. Valvular insufficiency, also called regurgitation, or incompetence, occurs when a valve does not close tightly. If the valves do not seal, some blood will leak backwards across the valve. Depending on which valve is affected, the conditioned is called tricuspid regurgitation, pulmonary regurgitation, mitral regurgitation or aortic regurgitation. People with valve disease (except mitra lvalve prolapse without thickening or regurgitation) are at increased risk for developing this life-threatening infection. According to A.P. Yoganathan et al. heart valve disease which affects commonly the mitral, aortic and tricuspid valves, is one of the main problems of the cardiovascular disease (2003). If one or more of the heart valves are impaired and unable to function properly, it is necessary to go for heart valve replacement surgery.
2.THE BJORK–SHILEY VALVE
Currently there are at least five types of prosthetic heart valves used clinically:
Mechanical ball valves, such as the Starr-Edwards mitral caged ball valve.
Mechanical tilting disk valves, such as the Medtronic Hall tilting disk valve.
Mechanical bileaflet valves, such as the St.Jude bileaflet valve.
Bioprosthetic valves from the pig, such as the D. Hancock porcine valve.
Bioprosthetic valves from the ox or cow, such as the E. Carpentier-Edwards bovine pericardial valve.
The Bjork–Shiley valve is a mechanical heart valve prosthesis. Beginning in 1971, it has been used to replace the aortic or mitral valves. It marks the first example of a successfully used tilting-disc valve. It was manufactured first by Shiley Inc., then later by Pfizer after that company purchased Shiley.
The Bjork valve consists of a single carbon-coated disc in a tantalum housing. The discs are held in place by two metal struts, an inflow and an outflow strut. The standard design Bjork–Shiley valve is a very durable valve and was widely used in the 1970s. The housing is an alloy called Haynes 25 which is a chromium cobalt alloy.
The Bjork-Shiley heart valve was the first successful example of a mechanical prosthesis with a tilting disk design. However, its plano-convex design was prone to thrombosis, so it was updated with an improved convexo-concave (CC) design that reduced the possibility of thrombus formation and sped up manufacturing. The CC valve was composed of a single carbon-coated disk, held in place by two metal struts, an inflow and an outflow, in a metal housing. The inlet strut was flush with the metal flange, but each end of the outlet strut was welded to it separately.
It had an option of several flange sizes ranging from 21 mm- 33 mm and of an opening angle of 60 degrees or 70 degrees. The B.S. valve was used to replace either the aortic or mitral valves. Changes in pressure up and down stream of the valve open and close the disk to regulate blood flow. The struts constrain the range of movement of the disc, allowing the disc to open to an angle of 60 or 70 degrees. The suture ring, made of Teflon, was sewn to the cardiac tissue to hold the valve in place.
2.3 DEVICE FAILURE:
The fractures could be Outlet strut fracture (OSF), Single leg fracture (SLF) and Single leg separation (SLS); OSF being the dominating one.
One end of the strut would fracture first, followed generally within a few months by a fracture of the other end. Fracture occurred from brief impacts on the outlet strut connections due to over-rotation of the disc closing with almost ten times the force of the disc opening. This created bending stresses beyond the strut’s fatigue endurance limit that eventually caused fatigue induced fracture after many occurrences of outlet tip overloading. Valve failure caused the disk to become free from the valve, so blood flow could no longer be regulated, leading to cardiac death if it was not detected in time. These fractures occurred during premarket trials and were assumed to be due to the strut welding.
2.4 FAILURE SYMPTOMS
If there is a fracture of the outlet strut, the normal clicking sound that occurs when the disc opens and closes will cease. Other symptoms are a sudden, sharp chest pain or a feeling of tight pressure that persists for more than a few minutes; sudden loss of consciousness, even if it is regained soon after; sudden, severe shortness of breath during normal activity; and a sudden, irregular or rapid heart beat.
3. CAUSES OF THE FAILURE OF B.S.HEART VALVE CAN BE SEEN FROM THREE BASIC PERSPECTIVES:
As the number of fractures began to increase, the Shiley Heart Valve Research Center initiated a number of studies to determine the cause of the outlet strut fractures (OSFs). Pulse duplicator studies demonstrated that (1) uneven pressure distribution across the disc at closure resulted in a tendency for the disc to over rotate, (2) there was a linear relation between outlet strut loads and the closing velocity, (3) outlet strut loads increased with increasing dP/dt and heart rate, and (4) valve-related factors such as the hook-to-well distance and hook deflection correlated with outlet strut load.
Broadly they can be grouped under-
A. Faulty design concept
The first cause of fracture which was not considered by the designers was the difference between the ideal closure and the biomedical closure of the disk. The biomedical closure causes contour miss match and induces high closing force on the disk. This contour miss match and high speed rotation of the disk shifts the contact point between the disk and the inlet strut from the design point (the base of the strut) to the a new location (tip of the strut) which in turn causes abnormal bending stress and residual excessive stress on the weld union (fracture site). Other sources of failure came from the size of the flange and tilting angle of the disk. It has been reported that the larger the size of the flange the higher the risk of occurrence of fracture and 70° B.S. valves were 6 times more prone to fracture than 60° B.S. valves .
B. Flawed manufacturing process
Manufacturing process was another source of strut fracture. The major contributors were below standard testing procedures especially less number of hook deflection testing, unacceptable quality of welding like crack in the weld, pores inside the weld and unaccepted weld penetration. The time of welding also contributed to the strut fracture where by the B.S. valves manufactured from January, 1981 to June, 1982 have had the higher rate of failure .
C. Characteristics of patients
The third contributing factor was the patients’ age and valve implant position. The hazard ratio for a patient who was below 50 years is two times more than the one who was above 50 years of age because of higher cardiac activities and the longer the period of implant the higher the risk of fracture.
The B.S. valve was implanted in patients from April 1st, 1979 to November 1, 1986 when the FDA removed it from the market. Approximately 82,000 valves were implanted worldwide, with about 25,000 in the United States. There have been about 500 cases of fracture reported and about two-thirds of those have resulted in death.
4.1 RECALL FACTORS:
After lawyers began taking depositions of Shiley employees in 1987, it was learned that paperwork was falsely filed during manufacturing. After searching through company documents, it was found that many valves were “re-welded” by a “phantom” employee # 2832. These were likely to have had cracks that were polished over by a worker during manufacturing, instead of being re-welded or discarded entirely.
4.2 RISK FACTORS FOR OUTLET STRUT FAILURE (OSF):
(a)Multivariate analysis identified wide opening angle (70 ° ), large valve size (?29 mm diameter), and young age (<50 years) as risk factors for OSF. To further explore the determinants of risk and their relative contribution to OSF, the panel sponsored additional case-control and cohort studies in both the US and Europe. The investigators concluded that “there was a strong inverse gradient of risk with age … Large mitral valves were at greatest risk of strut fracture … valves welded from mid-1981 through March 1984 were more likely to fracture than those manufactured in 1979 and 1980 … Body surface area <1.5 m 2 was associated with 1/16 the risk of body surface area of ?2.0 m 2 “. It was noted that differences in body surface area are related to gender, with women having smaller areas.
(b)The panel also sponsored follow-up to the 1992 Dutch study in which the manufacturing characteristics that predicted OSF in large 60 ° degree valves were studied. Results indicated that “age at implantation …, lot size …, number of hook deflection tests performed …, number of discs that were used …, and lot fracture percentage … as independent predictors of fractures”. The manufacturing data were provided by Pfizer for this review.
(c)Also sponsored by the panel was a study by Omarand who reported on OSF in the United Kingdom cohort of 2,977 patients with a follow-up of 18 years. There were 56 OSFs. The investigators identified age, body surface area, valve size, shop order, fracture rate, and manufacturing period as risk factors for OSF. They also noted that the risk of OSF in valves manufactured from 1981 to 1984 was 4× greater than that of valves manufactured before 1981.
Figure 1: The number of OSFs occurring each year from the earliest reported case in 1978. No fractures have been reported in 2010, 2011, and 2012.
In short risk factors therefore included those related to the valve:-
(i) Valve opening angle (70 ° vs 60 ° ) and diameter size (33 vs 21 mm) are the strongest determinants of fracture risk. . A valve with an opening angle of 70 degrees is six times more likely to fracture than 60 degree valves. Large valves, of flange size greater than 29 mm, are nearly four times more likely to fracture than small valves that are less than 29 mm.
(ii)Other significant but weaker determinants were related to specific aspects of the manufacturing process such as the fracture rate of the batch from which the valve originated, the amount of rework of valves, and the welder group.
(iii)Age and gender are the most important patient-related characteristics. The risk of fracture was only 1/2 as high among women compared with men, and risk decreased with increasing age. Fewer than 14% of the fractures occurred in those aged ?65 years.
In addition, younger patients will have the valve implanted for a longer period of time and thus have a greater cumulative risk of fracture over the course of their lifetime.
Risk Factor Category Estimated Relative Risk of OSF Estimated No. (%) of Valves With Attribute No. (%) of OSF With Attribute
Angle 70 ° 5.0 4,000 (5) 154 (24)
60 ° 1.0 ?81,700 (95) 479 (76)
Size (mm) 33 9.6 1,600 (2) 58 (10)
31 5.5 10,300 (12) 205 (33)
29 4.0 14,900 (17) 181 (28)
27, 23 2.8 32,200 (38) 155 (24)
25, 21 1.0 ?26,500 (31) 34 (5)
Weld date >1980 1.0 ?7,600 (9) 35 (5)
1980 0.5 18,400 (22) 45 (7)
January 1981 to June 1982 1.6 33,100 (39) 463 (74)
July 1982 to March 1984 1.0 18,500 (22) 89 (14)
April 1984 onward 0.0 8,000 (9) 0 (0)
Shop order OSF in other valves in batch <1% 1.0 ?69,800 (81) 231 (36)
OSF in other valves in batch 1%–5% 1.9 12,100 (14) 247 (39)
OSF in other valves in batch >5% 2.4 3,800 (4) 155 (24)
Welder group A or B 1.0 ?70,700 (82) 391 (62)
C 1.5 15,100 (18) 242 (38)
Position Mitral 2.5 38,100 (45) 496 (78)
Aorta 1.0 ?47,200 (55) 137 (22)
Rework status No crack or rework 1.0 ?78,100 (91) 538 (85)
Crack, rework, or missing 1.6 7,700 (9) 95 (15)
Table 1: Valve-related risk factors for outlet strut fracture (OSF) in 60 ° Björk-Shiley convexo-concave heart valves
4.3 ISSUES INVOLVED IN APPLYING GUIDELINES TO INDIVIDUAL PATIENTS:
The first issue relates to the difficulty in applying information obtained from group data to individual patients. The value of the guidelines is in identifying the subgroup of patients for whom, on average, B.S. heart valve reoperation will result in a gain in life expectancy.
The second issue is that the qualification for a monetary benefit should not be equated with the recommendation that replacement surgery is appropriate for a particular patient. This is because many patients are not in optimal health, and some facilities do not have significant experience in valve replacement surgery. Thus, when either of these assumptions is not met, the risk of surgery would increase and the likelihood of benefit to the patient would decrease.
Finally, although the guidelines define patients who are most likely to benefit from valve replacement surgery, they are based on probabilities, and thus on occasion, patients deemed at low risk may experience fracture. Although the percentage of fractures is considerably less than in the high-risk group, because the low-risk group itself is many-fold larger, the absolute numbers will be greater .
5. DECEIT AND DECEPTION
In 1990 the FDA became aware of occurrences of fracture and requested that Shiley notify all patients who received CC valves of the problems. Shiley did not recommend surgery to replace the valve because the reoperative risk of replacing it was thought to be greater than that of fracture of the intact valve. After results from the study done in Europe were published, the FDA required Shiley to again notify all patients with CC valves, this time informing them of an increased risk of fracture depending on patient and valve specifications. Patients were advised to speak to their doctors, who were also notified of the new fracture figures, about valve replacement. Those who had smaller valves or were older were assured that the new data did not affect them. In 1992, Pfizer Inc. and Shiley Incorporated negotiated a settlement with members of the Bowling class in the case called Arthur Ray Bowling, et al. v. Pfizer Inc., et al. Members of the Bowling class were defined as anyone who had received a B.S. valve.
Guidelines were developed to determine whether someone qualified for monetary benefits from the Bowling Patient Benefit Fund for elective prophylactic valve replacement. They have been revised several times, with the most recent update in 2003. Patient specific annual fracture rates must be estimated based on valve size, valve implant position, weld date, welder identity, valve shop order, and current patient age. Operative mortality calculations are found based on actual B.S. reoperations and from similar studies of elective valve explanations.
5.1 ACTIVITIES OF THE SUPERVISORY PANEL ESTABLISHMENT OF GUIDELINES FOR VALVE REPLACEMENT SURGERY:
The Bowling-Pfizer settlement agreement provided monetary benefit for those who had been injured by B.S. failure and for their families, as well as certain costs associated with valve replacement for those those in whom the risk of valve failure exceeded the surgical mortality/serious morbidity involved in valve replacement. The guidelines were therefore intended to identify patients in whom the meaningful extension of life expectancy provided by reoperation exceeded the potential loss due to valve fracture. In calculating this risk, the panel assumed that the patient was in optimal health for his or her age and that the facility where the surgery was to be performed had an excellent operative mortality record. This in turn required assembling data on the incidence of strut fracture, the risk factors associated with fracture, and the surgical mortality and morbidity data for valve reoperation.
Government claims with Shiley were resolved in a settlement in 1994, and the company paid $10.75 million in fines and reimbursements for payments the government made for the B.S. valves. Shiley also agreed to pay up to $10 million more for medical costs that the government incurred or would in the future due to fracture or elective replacement of valves. This agreement was made under the False Claims Act where Shiley made the following grievances:
falsely asserted that the CC valve caused fewer thrombosis events than other models;
falsely asserted that a series of manufacturing changes had corrected a serious design defect;
did not provide the FDA with all of the data it had concerning fractures during laboratory testing;
rebuilt scrap valves, re-welded valves an excessive amount of times, and polished cracked valve struts instead of re-welding them;
falsified employee identification numbers on over 3,000 reworked valves;
argued to keep the valve on the market even after fracture was noticed, claiming that the risk of fracture was outweighed by the decreased risk of blood-clotting.
6. ETHICAL ISSUES THAT AROSE AS A RESULT OF THE PROBLEM AND RECALL
The use of prostheses and implants raises issues of human identity and dignity because it involves the addition of artificial structures and systems to human biology, or even the replacement of human tissues and organs with artificial versions. Biomedical engineers have a responsibility to anticipate on the consequences of their designs for medical practice and to ensure that technologies and techniques are designed in a manner consistent with and supportive of ethical principles for medical practice.
On the technical side, the delicate nature of engineering a heart cannot be understated. If any component of the design fails abruptly, the patient has only moments to live. Because of the high level of risk, engineers and the companies they work for must necessarily be held to a higher standard of technical and moral accountability for their designs
The ethical principles of confidentiality, informed consent(consent to treatment based on proper understanding of the facts), justice (the equitable allocation of scarce health resources), dignity (dignified treatment of patients),were violated in this Pfizer heart valve case.
The Bjork-Shiley heart valve case presents ethical questions both for the system of regulation and for the individual responsibilities of a bioengineer.
(1) Shiley started its system regulation abuse by persuading the FDA that the B.S. valve thrombosis reduction ability was far better than the low rate of premarket accidental failures and got the approval in 1979 . The company deception continued by insisting a secrecy agreement not to release important information to FDA and doctors and as the company implements the “Earn as you learn” policy- continue supplying the product while investigation to understand the problem was going on resulted in 765 fractures and 480 deaths. There was loss of lives and was an act of fraud.
(2)The depositions of employees in 1987 revealed that the company falsify documents, re-welded fractured struts by phantom electrodes and polished cracked B.S. heart valves that should have been re-welded or discarded.
The failure of communication between the FDA and Pfizer was first caused by Pfizer misleading the FDA in the Premarket Approval Process (PMA). The lawsuit was filed when it became apparent that Pfizer had detected the strut flaw and adjusted the heart valve design without first informing the FDA. Also, manufacturing employees issued a misleading report to the FDA. Even if the FDA knew that B.S. valves failed during the premarket approval, it allowed the Shiley Company to provide the valves to the prosthesis market relaying on the “honor system” and the ethical values of the medical industry.
(3) Again, Shiley testifies by stating that the FDA approved the heart valve even when no clinical testing was needed (1). On the other hand, did he wait too long to take care of these precautions for the acclaimed deaths? From an ethical standpoint, Shiley should never have concealed the problems with the device. He also should have made a preemptive effort to fix the problem, not wait for a casualty (from a deontological point of view).
7. ETHICAL DILEMMAS
An ethical dilemma that Pfizer faced was how to prove the efficacy of the device by clinical testing. The FDA regulates this process by giving its mark of approval to products that meet certain guidelines; but in this case, this process was not properly adhered to. It is very difficult to confirm an organ design’s efficacy when there are many differences between clinical testing and other factors in real life. When they learned about the defect of the strut design, Shiley made the necessary corrections for it. However, he kept this information secret from the FDA and doctors who used the valve to treat their patients.
So the ethical dilemma would be either to continue to promote the product because it satisfies the statistical requirements, or to recall the product in name of the dangerous liabilities it entails regarding patients; there are too many risks of other failures that may cause great pain for patients. On top of removal from the market, the Shiley heart valve case resulted endorsement of strong regulation requirements on medical devices by FDA which failed to take action on Bjork-Shiley heart valve in time .
Had the company conducted itself properly, it is likely that the Bjork-Shiley valve would still be on the market. Studies showed that the real problem was not the design of the heart valve itself. If the strut welding had only been made more secure, the whole ordeal might have been avoided . Plainly speaking, Pfizer’s deceptive practices in marketing, such as continuing to minimally refurbish defective models, resulted in many needless medical complications and deaths in its customers. This could have been avoided if Pfizer was honest with the FDA and medical professionals.
Without a doubt, it was not only Pfizer who was accountable. In this case, the FDA must also be included. Before going on the market, the new Bjork-Shiley heart valve was granted approval by the FDA, who would be responsible for monitoring the company’s manufacturing every two years. However, it was claimed that the FDA also did not test the pacemaker rigorously enough in the pre-market approval process. Furthermore, the FDA failed to inspect the plant according to schedule.
To sum up, the Bjork-Shiley tilting disk heart valve was intended to overcome the intense requirement of anticoagulant and thrombosis which was the main problems of the caged-ball heart valves. There is no doubt that it highly reduced thrombosis effect but due to faulty design concept, flawed manufacturing practices and characteristics of patients it was accompanied by outlet strut fracture and claimed many lives.Even if the Shiley company knew the occurrence of fracture, it implements the “Earn as you learn” policy and continued supplying the product while investigating the problem. It can be clearly seen that the medical devices regulatory requirements were not strong enough to enable the FDA to take action on the B.S. heart valve in time.The Bjork-Shiley heart valve case presented ethical questions both for the system of regulation and for the individual responsibilities of bioengineer. In addition to withdrawal of the B.S. heart valve from the market in 1986, the case also enabled the FDA to ratify strong regulation requirements on medical devices. Finally the company incurred $20.75 million fine by the government and spent a lot of money to create a continuing fund for researches to follow up the B.S. valve integrity non-invasively.
1991, ‘Ethical issues in biomedical engineering: the Bjork-Shiley heart valve’, IEEE Engineering in Medicine and Biology Magazine Online, Vol. 10
2007, Bjork-Shiley Heart Valve Recall Online, Available from:; http://biomed.brown.edu/Courses/BI108/BI108_2007_Groups/group05/pages/bjork_shiley.html