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Heart valves: Ten commandments and still counting
Heart Valves: Ten Commandments and Still Counting Dwight Emary Harken, MD Harvard Medical School, Boston, Massachusetts
The ceremonial occasions of life have been so endlessly repeated that the wiser the observation they invoke the more time worn they are. Vermont Royster
S
o it is with prosthetic heart valves. We know where we want to go, but it appears to be nearly impossible to get there from here. In the 1950s I defined Ten Commandments for the prosthetic valve, still often quoted but not met. 1. It must not propagate emboli. 2. It must be chemically inert and not damage blood elements. 3. It must offer no resistance to physiological flows. 4. It must close promptly (less than 0.05 second). 5. It must remain closed during the appropriate phase of the cardiac cycle. 6. It must have lasting physical and geometric features. 7. It must be inserted in a physiological site (generally the normal anatomical site). 8. It must be capable of permanent fixation. 9. It must not annoy the patient. 10. It must be technically practical to insert.
Historical Perspective In the 1950s, my colleagues and I had found some diseased valves that were impossible to repair. When debriding calcific aortic stenosis, we often debrided to no valve. Such crises caused us to work feverishly in the laboratory, where none of our animals survived aortic valve replacement with a prosthesis. Hufnagel’s chambered-ball valve in the descending aorta showed us several things: durability, acceptable sound level with silicone balls, and possibly (erroneously) acceptable thrombogenicity. However, physiologically the valve had to be beneath the coronary ostia where we thought a caged-ball valve could be implanted. Much work followed to determine the ball to base orifice ratio: if the height of the cage was too tall, there was too much regurgitation in closing; if the cage was too short, the valve was obstructive. Hufnagel gave us the silicone balls. The work also focused on pulse duplicators (a great assemblage of artifacts). Some accelerated wear studies were a further source of misinformation. We built a caged-ball valve that seemed reasonable. We feared that if Presented at the World Congress on Heart Valve Replacement, San Diego, CA, Jan 15-18, 1989. Address reprint requests to Dr Harken, Doctors’ Office Building, Suite 516, 300 Mt. Auburn St, Cambridge, MA 02138.
0 1989 by The Society of Thoracic Surgeons
the valve tilted, contact with the aortic wall might interfere with poppet movement, so we installed an outer cage. Starr showed this to be unnecessary. Clinically we had extensive exposure to a malignant syndrome of aortic valve disease, ie, angina, syncope, and congestive heart failure unresponsive to medical treatment. We collected 87 such patients between 1950 and 1960. Seventy-seven were dead within 7 months. We did not have to have a perfect valve; we just had to have a good one. At a hearing in Washington, DC, I was asked, ”What is a safe device?“ I answered, “A device is safe when it is safer than the condition it corrects.” To that Dr Arthur Beall added, “And is the best available.” These two responses are widely quoted as the definition of a safe device: “A device is safe when it is safer than the condition it corrects and is the best available.” Extensive experience (some of it quite unhappy) with open debridement and open valvoplasty taught us how to approach and implant prostheses. There were 2 survivors among the first 7 patients, 1 of whom had operation on March 10, 1960, and the other, June 6, 1960. Both have undergone valve replacement, 1 at 3 years for paravalvular leak and 1 at 22 years for bacterial endocarditis, and both are alive today. The ball valve has been far less satisfactory in the mitral position. The ball, though isobaric with blood, still has inertia, and with low atrial opening pressures, inertia becomes important. Ball valves occupy considerable space and reduce stroke volume and cardiac output. In small ventricles, ball valves can obstruct the outflow tract and even produce arrhythmias and damage by impinging on the septum.
National Implant Registry
,
This is all history, but it does bring up the National Implant Registry. Like so many of you, I had reservations about having the problems with our device aired. However, that is what we must have. In fact, be the implant a valve, pacemaker, artificial joint, or whatever, it is wholesome to have a wide survey service. I find it impossible to personally cover the entire professional literature. The media broadsides often cause inappropriate alarm. Many of our patients with a pacemaker or valve have been frightened by nonspecific press releases. The National Implant Registry offers appropriate specificity and relief to the majority. In short, I think we need more critical assessment of malfunction, and will cite one example of why I believe this. A 62-year-old housewife had a Harken low-profile Ann Thorac Surg 1989;48:S18-9
0003-4975/89/$3.50
Ann Thorac Surg
HARKEN TEN COMMANDMENTS OF HEART VALVES
1989;48:S1%9
mitral prosthesis placed in 1969. I had taken the dimensions of Bud Kay’s Kay-Suzuki valve, which offered superb hemodynamics but had been known to cock. I copied his specifications, but rounded the silicone poppet edge for longer wear and impregnated the silicone with barium for wear evaluation by cinefluoroscopy. A wear study embraces a cinefluoroscopy in precise silhouette; flattening of the round atrial poppet edge indicates wear. The wear study in October 1988 showed no change during the past year. A month later, the poppet escaped. In an emergency operation in November, Dr Peter Marquis Siedl of Fort Myers retrieved the poppet and replaced the prosthesis with a St. Jude valve. Thanks to his genius, the patient is alive and well. We must have more sensitive signals for replacement. The studies of Matloff and Chaux have suggested that; the National Implant Registry has warned us.
3.
4.
Anticoagulation
S19
safer than regulation by the many available pastel shades and sizes. Patients know how many tablets they take, not how many milligrams. This is especially important when patients change geographical areas or physicians. Instruct all laboratories to give the prothrombin time results to the patients as well as to the physician, and to give this time in seconds (not percentages or ratios). Strive for a prothrombin time, in seconds, 1.5 times the control. One and one-half times the control is easy to understand and has high and low safety margins. We formerly recommended two times the control or a little less. That made it too easy to drift dangerously upward. We are now assured by the anticoagulant oracles that a little less than 1.5 times the control is safe. It is not. It is too close to the dangerously low level. Strive for 1.5 times the control, and let the patients know it. Tell patients that if they drift more than 3 seconds higher or lower than this, they should call their doctor or their anticoagulation center. Have all patients on a regimen of anticoagulants have a prothrombin time determination at least once a month and more often if it is unstable. If anticoagulants must be electively reversed, taper them; in an emergency, use fresh frozen plasma, not vitamin K. As reversal is often associated with dental work, remember that a simple extraction does not necessarily require reversal but it does require antibiotic coverage when there are cardiovascular indications for anticoagulation. Stress this to patients.
Finally, I must discuss a blinding glimpse of the obvious. We heart surgeons as no other group are creating a crisis in anticoagulation. Safe anticoagulation is difficult if not impossible. The way it is conducted worldwide leaves much to be desired. The way we allow our patients to be managed on anticoagulation is alarming. The number of patients who assume that ”I will be notified if the level of anticoagulation is not right” is appalling. Frequently, patients are not notified. Physicians go on holiday, and secretaries do not always transmit the laboratory reports. Reporting systems are not standard. Many patients have no idea of their prothrombin level or what that means. I urge the adoption of a national program, the points of which are as follows:
5.
1. Educate patients about the use of warfarin sodium just as diabetics are educated about diet and insulin. Anticoagulants are just as important and are easier to understand. 2. Prescribe Coumadin (crystalline warfarin sodium) only in 5-mg tablets. Regulation in multiples or fractions is
rocky road. I have saluted the National Implant Registry and stressed the need to be alert to the modes of valve malfunction. I have pled the cause of safer anticoagulation. We have worshipped at the shrine of the Ten Commandments for the prosthetic valve, but we are still counting. We are still sinners.
6.
Conclusion I have defined the goals and described the start up that
The ceremonial occasions of life have been so endlessly repeated that the wiser the observation they invoke the more time worn they are. Vermont Royster
S
o it is with prosthetic heart valves. We know where we want to go, but it appears to be nearly impossible to get there from here. In the 1950s I defined Ten Commandments for the prosthetic valve, still often quoted but not met. 1. It must not propagate emboli. 2. It must be chemically inert and not damage blood elements. 3. It must offer no resistance to physiological flows. 4. It must close promptly (less than 0.05 second). 5. It must remain closed during the appropriate phase of the cardiac cycle. 6. It must have lasting physical and geometric features. 7. It must be inserted in a physiological site (generally the normal anatomical site). 8. It must be capable of permanent fixation. 9. It must not annoy the patient. 10. It must be technically practical to insert.
Historical Perspective In the 1950s, my colleagues and I had found some diseased valves that were impossible to repair. When debriding calcific aortic stenosis, we often debrided to no valve. Such crises caused us to work feverishly in the laboratory, where none of our animals survived aortic valve replacement with a prosthesis. Hufnagel’s chambered-ball valve in the descending aorta showed us several things: durability, acceptable sound level with silicone balls, and possibly (erroneously) acceptable thrombogenicity. However, physiologically the valve had to be beneath the coronary ostia where we thought a caged-ball valve could be implanted. Much work followed to determine the ball to base orifice ratio: if the height of the cage was too tall, there was too much regurgitation in closing; if the cage was too short, the valve was obstructive. Hufnagel gave us the silicone balls. The work also focused on pulse duplicators (a great assemblage of artifacts). Some accelerated wear studies were a further source of misinformation. We built a caged-ball valve that seemed reasonable. We feared that if Presented at the World Congress on Heart Valve Replacement, San Diego, CA, Jan 15-18, 1989. Address reprint requests to Dr Harken, Doctors’ Office Building, Suite 516, 300 Mt. Auburn St, Cambridge, MA 02138.
0 1989 by The Society of Thoracic Surgeons
the valve tilted, contact with the aortic wall might interfere with poppet movement, so we installed an outer cage. Starr showed this to be unnecessary. Clinically we had extensive exposure to a malignant syndrome of aortic valve disease, ie, angina, syncope, and congestive heart failure unresponsive to medical treatment. We collected 87 such patients between 1950 and 1960. Seventy-seven were dead within 7 months. We did not have to have a perfect valve; we just had to have a good one. At a hearing in Washington, DC, I was asked, ”What is a safe device?“ I answered, “A device is safe when it is safer than the condition it corrects.” To that Dr Arthur Beall added, “And is the best available.” These two responses are widely quoted as the definition of a safe device: “A device is safe when it is safer than the condition it corrects and is the best available.” Extensive experience (some of it quite unhappy) with open debridement and open valvoplasty taught us how to approach and implant prostheses. There were 2 survivors among the first 7 patients, 1 of whom had operation on March 10, 1960, and the other, June 6, 1960. Both have undergone valve replacement, 1 at 3 years for paravalvular leak and 1 at 22 years for bacterial endocarditis, and both are alive today. The ball valve has been far less satisfactory in the mitral position. The ball, though isobaric with blood, still has inertia, and with low atrial opening pressures, inertia becomes important. Ball valves occupy considerable space and reduce stroke volume and cardiac output. In small ventricles, ball valves can obstruct the outflow tract and even produce arrhythmias and damage by impinging on the septum.
National Implant Registry
,
This is all history, but it does bring up the National Implant Registry. Like so many of you, I had reservations about having the problems with our device aired. However, that is what we must have. In fact, be the implant a valve, pacemaker, artificial joint, or whatever, it is wholesome to have a wide survey service. I find it impossible to personally cover the entire professional literature. The media broadsides often cause inappropriate alarm. Many of our patients with a pacemaker or valve have been frightened by nonspecific press releases. The National Implant Registry offers appropriate specificity and relief to the majority. In short, I think we need more critical assessment of malfunction, and will cite one example of why I believe this. A 62-year-old housewife had a Harken low-profile Ann Thorac Surg 1989;48:S18-9
0003-4975/89/$3.50
Ann Thorac Surg
HARKEN TEN COMMANDMENTS OF HEART VALVES
1989;48:S1%9
mitral prosthesis placed in 1969. I had taken the dimensions of Bud Kay’s Kay-Suzuki valve, which offered superb hemodynamics but had been known to cock. I copied his specifications, but rounded the silicone poppet edge for longer wear and impregnated the silicone with barium for wear evaluation by cinefluoroscopy. A wear study embraces a cinefluoroscopy in precise silhouette; flattening of the round atrial poppet edge indicates wear. The wear study in October 1988 showed no change during the past year. A month later, the poppet escaped. In an emergency operation in November, Dr Peter Marquis Siedl of Fort Myers retrieved the poppet and replaced the prosthesis with a St. Jude valve. Thanks to his genius, the patient is alive and well. We must have more sensitive signals for replacement. The studies of Matloff and Chaux have suggested that; the National Implant Registry has warned us.
3.
4.
Anticoagulation
S19
safer than regulation by the many available pastel shades and sizes. Patients know how many tablets they take, not how many milligrams. This is especially important when patients change geographical areas or physicians. Instruct all laboratories to give the prothrombin time results to the patients as well as to the physician, and to give this time in seconds (not percentages or ratios). Strive for a prothrombin time, in seconds, 1.5 times the control. One and one-half times the control is easy to understand and has high and low safety margins. We formerly recommended two times the control or a little less. That made it too easy to drift dangerously upward. We are now assured by the anticoagulant oracles that a little less than 1.5 times the control is safe. It is not. It is too close to the dangerously low level. Strive for 1.5 times the control, and let the patients know it. Tell patients that if they drift more than 3 seconds higher or lower than this, they should call their doctor or their anticoagulation center. Have all patients on a regimen of anticoagulants have a prothrombin time determination at least once a month and more often if it is unstable. If anticoagulants must be electively reversed, taper them; in an emergency, use fresh frozen plasma, not vitamin K. As reversal is often associated with dental work, remember that a simple extraction does not necessarily require reversal but it does require antibiotic coverage when there are cardiovascular indications for anticoagulation. Stress this to patients.
Finally, I must discuss a blinding glimpse of the obvious. We heart surgeons as no other group are creating a crisis in anticoagulation. Safe anticoagulation is difficult if not impossible. The way it is conducted worldwide leaves much to be desired. The way we allow our patients to be managed on anticoagulation is alarming. The number of patients who assume that ”I will be notified if the level of anticoagulation is not right” is appalling. Frequently, patients are not notified. Physicians go on holiday, and secretaries do not always transmit the laboratory reports. Reporting systems are not standard. Many patients have no idea of their prothrombin level or what that means. I urge the adoption of a national program, the points of which are as follows:
5.
1. Educate patients about the use of warfarin sodium just as diabetics are educated about diet and insulin. Anticoagulants are just as important and are easier to understand. 2. Prescribe Coumadin (crystalline warfarin sodium) only in 5-mg tablets. Regulation in multiples or fractions is
rocky road. I have saluted the National Implant Registry and stressed the need to be alert to the modes of valve malfunction. I have pled the cause of safer anticoagulation. We have worshipped at the shrine of the Ten Commandments for the prosthetic valve, but we are still counting. We are still sinners.
6.
Conclusion I have defined the goals and described the start up that