The silver anniversary of cardiac valve replacement

FROM THE EDITOR

he Silver Anniversary of Cardiac Valve Replacement

The year was 1960. Forty-three-year-old John Fitzgerald Kennedy was elected president of the USA; 18year-old Bobby Fischer successfully defended his US chess championship; To Kill a Mockingbird by Harper Lee and The Rise andFall of the Third Reich by William Shirer were published: birth control pills were made available to the public; Polaris missiles were successfully fired from a submerged atomic submarine; the International System of Units (Sl), based on the metric system, was adopted as the worldwide standard at a General Conference on Weights and Measures; Theodore Maiman, physicist, developed the first LASER (Light Amplification by Stimulated Emission of Radiation), and successful, i.e., prolonged survival, cardiac valve replacement occurred. When the annals of cardiology are written, 1960 will be remembered as the time that cardiac valve replacement became a predictably successful reality. Since 1960, over 1 million dysfunctioning native cardiac valves have been replaced with a mechanical prosthesis or a bioprosthesis (tissue valve). If lasers prove successful for coronary artery disease, 1960 will acquire additional importance for cardiology. Dwight Harken was the first to use a mechanical prosthesis successfully in the natural anatomic cardiac valve position. Charles Hufnagel in October 1952 had used a caged-ball prosthesis in the descending thoracic aorta for severe aortic regurgitation but the insertion in this position of course only partially decreased the amount of regurgitant flow during ventricular &stole.’ It was obvious that the prosthesis had to be inserted proximal to the coronary arterial ostia to completely relieve the regurgitant flow and to have any effect in patients with aortic valve stenosis. The lucite ball used initially by Hufnagel was eventually changed by him to a hollow nylon core covered by silicone rubber so that it would be less noisy and also so that it would be isobaric with blood. Hufnagel gave Harken several of his hollow-nylon-silicone-rubber-covered poppets and Harken used them in his stainless steel double-caged prosthesis. Later, he used solid silicone rubber poppets. The outer cage prevented the poppet from touching the wall of aorta in its excursion. Harken’s first aortic valve replacement using the caged-ball prosthesis with an Iva-

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Ion@ aorta-widening gusset extending cephalad from the prosthetic attachment ring was unsuccessful.* His second patient, a 32-year-old woman who had had a previous transaortic valvuloplasty, underwent successful aortic valve replacement on March IO, 1960. Harken was nearly 50 years old at the time. The patient later developed significant peribasilar prosthetic regurgitation and the prosthesis was replaced in 1963. This patient is still alive in 1985. Harken had 2 survivors among his first 7 patients having aortic valve replacement with his caged-ball pr0sthesis.s The second successful operation was performed on June 7, 1960. This patient developed prosthetic endocarditis 23 years later, the prosthesis was replaced, and this patient is still alive in 1985. Thus, the initial prosthesis was in place for 23 years, the longest any prosthetic valve had been in place, and the poppet at reoperation “looked good.” Neither of Harken’s first 2 successful human aortic-valve-replacement patients ever received anticoagulants and neither apparently has had embolic complications. The first successful mitral valve replacement was performed by Albert Starr in September 1960.4 Although successful aortic valve replacement had never been accomplished in nonhuman animals before Harken’s success in patients, Starr had successfully used a caged-ball prosthesis in dogs for mitral valve replacement before his attempt in humans. Indeed, he had canine survivors of mitral valve replacement with caged-ball prostheses for many months before he attempted, at the encouragement of his cardiologist colleague, Herbert Griswald, mitral valve

Dwight Harken (left) and Albert Starr successful cardiac valve replacement.

(right)

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the time

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replacement in a human patient. His first mitral valve replacement with a fully engineered caged-ball prosthesis was in a 33-year-old woman who had an air embolus at operation and she died 10 hours’later. The second patient in whom 34-year-old Albert Starr performed mitral valve replacement was a 52-year-old truck dispatcher, who also received a caged-ball prosthesis, and he lived for 15 years thereafter. After Starr presented his results of mitral valve replacement in March 1961 before the American Surgical Association, Michael E. DeBakey5 commented as follows: “I must say that this paper persuades me to reevaluate my attitude toward ball valves. I have been somewhat prejudiced against them because of my very early experience with their use in changing the directional flow in blood pumps. Our most recent experience with the use of such ball valves, as in the Hufnagel valve in aortic insufficiency, also tended to make me somewhat prejudiced . . . Nonetheless, it seems to me that this is very impressive work on the part of Drs. Starr and Edwards . . .” Shortly after that surgical meeting, Starr visited Boston and observed Harken insert his double caged-ball prosthesis into the sot-tic valve position in a patient. At the time Starr became convinced that his fully engineered, single unit, caged-ball prosthesis, which he had used in the mitral position, also could be adapted to the aottic valve position. Thus, he and his engineering associate, Lowell M. Edwards, * also developed a factory-complete, caged-ball prosthesis for use in the aortic valve position and Starr later successfully used it for aortic valve replacement. During the past 25 years Starr has continued to use the caged-ball prosthesis (Starr-Edwards) as his first choice among mechanical prosthetic valves. Harken, in contrast, later considered the caged-ball type to be far less desirable than some tilting disc prostheses. Although other varieties of caged-ball prostheses (Magovern, Smeloff-Cutter, Braunwald-Cutter and DeBakey) followed the Harken and Starr-Edwards models, all but the Starr-Edwards type were discontinued. The StarrEdwards caged-ball prosthesis underwent several changes before returning to an early model. The early processing procedures for the silicone rubber poppets proved to be poor and as a consequence many of the silastic poppets

* Mr. Edwards at the time was a retired electrical engineer. During World War II he had designed a special airplane fuel pump that greatly contributedto the war effort. This pump handled mixtures of fuel in liquid and vapor phases. After retirement, as head of his own development company, he desired to continue to apply his knowledge by any contribution he might make to medicine. In 1958, he began working with Dr. Starr. Mr. Edwards, using his own laboratory facilities, was able to fabricate rapidly many prototype mitral valves for Dr. Starr to insert in experimental animals. Together, Edwards and Starr progressed through Teflon,@ Lucite,@ and silicone leaflet and ball-valve designs, and finally settled on a Teflon-rimmed stainless steel cage enclosing a silicone rubber ball.6

inserted before 1967 swelled by adsorbing lipids and some impacted in the cage; or they shrank or cracked and some dislodged from the cage. Although there have been some surface abrasion injuries, some to an extent that has allowed expulsion of the poppet from the cage, degeneration (variance) of the silicone rubber poppet of the fatty infiltration type has not been reported since the processing of the silicone was finally standardized in 1966. The use of cloth on the metallic struts as a means to decrease prosthetic thrombus in the Starr-Edwards model proved not to be an improvement. The hollow, metallic poppet, introduced almost simultaneously with the cloth covering of the metallic struts, caused disruption of the cloth on both base and stents, and this poppet and the cloth covering on the stents and the metallic studs on the metallic base have all been discontinued. Thus, a full circle has occurred with the caged ball. The only one presently manufactured in the USA is the model introduced in late 1965 and it consists of a silicone rubber poppet and non-cloth-covered stents and base (M 6 120 in the mitral valve position and A 1260 in the aortic valve position). Other prosthetic cardiac valves followed the caged ball. The first was a nontilting caged disc (1965), which was utilized by most surgeons only in the atrioventricular valve positions.7x8 This prosthesis proved to be highly thrombogenic and obstructive and its use has virtually disappeared. The next development was the tilting disc and the Bjork-Shiley prosthesis proved to be highly effective.g-‘l And, in the late 1970s another tilting disc appeared, this one with a bileaflet configuration, the St. Jude Medical Prosthesis; it is the least obstructive and the least damaging to blood elements of any of the prosthetic valves.12 Tissue values, of course, also have been used as replacements for dysfunctioning native aortic valves. Aortic valve homografts were first used for aortic valve replacement in the early 1960s.13-‘5 The initial results were gratifying: The valve lesions were usually ameliorated and anticoagulant therapy was not required. The problem proved to be accelerated wear with development of aortic regurgitation.16-‘g Other tissue valves followed, namely fascia lata, dura mater, parietal pericardium (human and bovine) and porcine aortic valve. The fascia lata and dura mater valves rapidly proved to be poor valve substitutes because they became stiff and relatively immobile. The porcine xenograft and bovine parietal pericardial valves preserved in glutaraldehyde and attached to a semiflexible stent proved to be effective. *O (The porcine bioprosthesis failed quickly when preserved in formalin.21) I have examined at necropsy well over 1,000 hearts containing 1 or more prosthetic or bioprosthetic cardiac valves.22-47 From my vantage point some views on cardiac valve replacement have been acquired and some of them are discussed in the remainder of this piece.

SeDtember

1. Perform cardiac valve replacment only when absolutely necessary. When I was a student in Emory medical sohool, the chief of surgery, .I f’I. Martin, often stated: “Never remove someone’s stomach unless it is absolutely necessary.” Certainly the same can be said of a cardiac valve. Except possibly in patients with severe, usually pure, aortic regurgitation, cardiac valve replacement should be reserved for patients with clear-cut evidence of significant cardiac dysfunction (functional class III or IV, New York Heart Association classification). Cardiac valvular operations that preserve the native valve, in my view, should be performed more often. Mitral valvuloplasty (commissurotomy) now is too often displaced in favor of mitral valve replacement,48s4g and mitral and tricuspid valve reparative operations for pure regurgitation probably are too often displaced by valve replacement. Tricuspid valve replacement for pure tricuspid regurgitation secondary to mitral valve disease usually can be avoided. The tricuspid valve position simply is not ideal for either a mechanical prosthesis as a bioprosthesis. 2. If anticoagulants are going to be administered chronically postoperative/y (because of “chronic atrial fibrillation or a huge left atrial cavity”), a mechanical prosthesis, not a bioprosthesis, should be used for valve replacement. The only advantage of a bioprosthesis is that use of this type of substitute cardiac valve does not require the use of anticoagulants. If anticoagulants are going to be used chronically postoperatively, use of a bioprosthesis cannot be justified. 3. In patients having double- or triple-valve replacement, either mechanical prostheses or bioprostheses, not both, should be used in a// native valve positions. Utilizing a mechanical prosthesis in one valve position and a bioprosthesis in another is illogical because anticoagulants will be required because of the mechanical prosthesis. All bioprostheses will wear out if the patients survive long enough, and presently available mechanical valves are far more resistant to wear. Thus, because anticoagulants will have to be given if one of the native valves is replaced by a prosthesis, all valves replaced should be replaced by a mechanical prosthesis, or bioprostheses should be used for all native valves replaced. 4. Bioprostheses should never be used in patients younger than age 20 years and, if possible, not in patients younger than age 30 years. 37 Because not all patients can take anticoagulants, bioprosthetic (tissue) cardiac valves must be available, but except in older persons or in women wanting pregnancy or in vigorous outdoor persons in whom chronic anticoagulation might have excessively dangerous consequences, bioprostheses should be second-line rather than first-line cardiac valve substitutes. Persons having third or fourth valve replacements need mechanical prostheses, not bioprostheses, because each operation is

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more dangerous than the preceding one, and bioprostheses wear out. 5. It is better to err on the side of using smaller-sized prostheses ramer iirarr Liger-&zed prostheses. After deciding which type of prosthesis or bioprosthesis to utilize in a particular patient, the next most important decision is which size of prosthesis or bioprosthesis to use.34 Although the sizing is generally not done until cardiotomy or aortotomy has been performed, the size of a substitute valve chosen should take into consideration the lean weight of the patient and the type of hemodynamic valvular lesion present and, in my view, roughly decided on before the patient and the surgeon enter the operating room. Volume lesions, of course, if chronic, dilate the ventricular cavity and usually the ascending aorta, and consequently larger-sized prostheses can usually be used. Pressure lesions, in contrast, mitral stenosis or aortic stenosis, or both, may not be associated with left ventricular dilatation and, consequently, a smaller-sized prosthesis or bioprosthesis will be required for the mitral position. Although the aortic root is usually dilated in chronic, isolated aortic stenosis and/or isolated regurgitation, when combined with chronic mitral valve stenosis or regurgitation, the aortic root is usually not dilated irrespective of whether the aortic valve is stenotic or purely regurgitant. Thus, in patients with combined mitral and aortic valve stenosis, or combined mitral and aortic regurgitation or mixed lesions, a smaller-sized prosthesis or bioprosthesis usually is preferred in the aortic valve position. 6. Refrain from doing mitral valve replacement in th presence of massive mitral anular calcium. 7. Use interrupted sutures only for insertion of either prosthetic or bioprosthetic cardiac valves. A single break of a continuous suture, despite 4 or 8 interrupted sutures, can produce massive regurgitation. 8. Operative preciseness is far more important during insertion of tilting disc prostheses than during insertion of caged-bail prostheses. A single suture may cause irreversible interference to closure of an occluder of a disc valve but may have no effect with a caged-ball prosthesis.38 Careful orientation is far more important with tilting-disc prostheses than with caged-ball ones. The margin of error, in other words, is less with tilting-disc prostheses compared to caged-ball prostheses or bioprostheses. 9. Predictably successful cardiac valve replacement can be achieved most often by surgeons who frequently perform cardiac valve replacement. Although over 50 % of prosthetic and bioprosthetic cardiac valves are supplied to surgeons who order relatively few substitute valves, predictably successful cardiac valve replacement cannot be obtained by an operator who only occasionally performs cardiac valve replacement. Predictable success requires a good prosthesis or bioprosthesis, a properly-sized

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prosthesis or bioprosthesis, an absence of significant, associated, unpalliated valvular’ or coronary heart disease, or both, a good surgeon and good postoperative care.

William C. Roberts, MD Editor in Chief References 1. Hufnagel CA, Harvey WP. The surgical correction of aortic regurgitation. Preliminary report. Bull Georgetown Univ Med Ctr 1953;6:60-61. 2. Harken DE, Soroff HS, Taylor WJ, Lefemlne AA, Gupla SK, Lunzer S. Partial and complete prostheses in aortic insufficiency. J Thorac Cardiovasc Surg 1960;6:744-762. 3. Harken DE Tavlor WJ. LeFemine AA. Lunzer S. Low HBC. Cohen ML. Jacobey JA: Aohic valve replacement with a caged ball valve. Am J Cardiol 1962;9:292-299. 4. Starr A, Edwards ML. Mitral replacement. Clinical experience with a ballvalve prosthesis. Ann Surg 1961;154:726-740. 5. DeBakey ME.Discussion of Albert Starr’s presentation. In Ref. 4:740. 6. Blalock A. Cardiovascular suroerv. oast and oresent. J Thorac Cardiovasc ’ Surg 1966;51:153-167. - ’ 7. Hufnagel CA, Conrad PW. Comparative study of some prosthetic valves for aortic and mitral reolacement. Suraerv 1965:57:205-210. a. Kay EB, Suzuki A, Demaney M, Zimmerman HA. Comparison of ball and $is,” valves for mitral valve replacement. Am J Cardiol 1966;18:504”

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Wada J. Knotless suture method and Wada hingeless valve. Jpn J Thorac Suro 1967:15:88-94. 10. Ka&er RL, iittehei CW. A new cageless free-floating pivoting disc prosthetic heart valve: design, development and evaluation, Stockholm, 1967, Digest ;fgp 7th lnternatronal Conference on Medical and Biological Engineering: 11. 12.

13. 14. 15. 16. 17. 18. ix: 21. 22. 23. 24.

Bjork VO. A new tilting disc valve prosthesis. Stand J Thorac Cardiovasc Surg 1969;3:1-10. Nicoloff DM, Emery RW, Arom KV, Northrup WF III, Jorgensen CR, Wang Y, Lindsay WG. Clinical and hemodynamic results with the St. Jude Medical cardiac valve prosthesis. A three-year experience. J Thorac Cardiovasc Surg 1981;82:674-883. Ross DN. Homograft replacement of the aortic valve. Lancet 1962;2: 487. Duran CG, Gunning AJ. A method for placing a total homologous aortic valve in the subcoronary position. Lancet 1962;2:488-489. Barratt-Boyes BG. Homograft aortic valve replacement in aortic incompetence and stenosis. Thorax 1964;19:131-150. Ross D. Biologic valves. Their performance and prospects. Circulation 1972:45:1259-1272. Angel1 WW, Shumway NE, Kosek JC. A five-year study of viable aortic valve homografts. J Thorac Cardiovasc Surg 1972;64:329-339. Wallace RB, Londe SP, Titus JL. Aortic valve replacement with preserved aortic valve hemografts. J Thorac Cardiovasc Surg 1974;67:44-52. Wallace RB. Tissue valves. Am J Cardiol 1975;35:866-871. Rels RL, Hancock WD, Yarbrough JW, Glancy DL, Morrow AG. The flexible stent. A new concept in the fabrication of tissue heart valve prostheses, J Thorac Cardiovasc Surg 1971;62:683-695. Yarbrough JW, Roberts WC, Reis AL. Structural alterations in tissue cardiac valves implanted in patients and in calves. J Thorac Cardiovasc Surg 1973;65:364-375. Roberts WC, Morrow AG. Mechanisms of acute left atrial thrombosis after mitral valve replacement. Pathologic findings indicating obstruction to left atrial emptying. Am J Cardiol 1966;1:497-503. Roberts WC, Morrow AG, Late postoperative pathologic findings after cardiac valve replacement. Circulation 1967;36:1-48-l-62. Roberts WC, Morrow AG. Causes of early postoperative death following cardiac valve replacement. Clinico-pathologic correlations in 64 patients

studied at necropsy. J Thorac Cardiovasc Surg 1967;54:422-437. 25. Roberts WC, Morrow AG. Anatomic studies of hearts containing caged-ball prosthetic valves. Johns Hopkins Med J 1967;121:271-295. 28. Roberts WC, Morrow AG. Compression of anomalous left circumflex coronary arteries by prosthetic valve fixation rings. J Thorac Cardiovasc Sura 1969:57:834-838, 27. Shepard RL, Glacy DL, Stinson EB, Roberts WC. Hemodynamic confirmation of obstruction to left ventricular inflow by a caged-ball prosthetic mitral valve. Case report. J Thorac Cardiovasc Surg 1973;65:252-254. 28. Roberts WC, Butkley BH, Morrow AG. Pathologic anatomy of cardiac valve replacement: a study of 224 necropsy patients. Prog Cardiovasc Dis 1973;15:539-587. treatment of hypertrophic obstructive cardiomy29. Roberts WC. Operative opathy. The case against mitral valve replacement. Am J Cardiol 1973; 32:377-381. 30. Seningen RP, Bulkley BH, Roberts WC. Prosthetic aortic stenosis. A method to prevent its occurrence by measurement of aortic size from preoperative aortogram. Circulation 1974;49:921-924. 31. Fishbein MC, Roberts WC, Golden A, Hufnagel CA. Cardiac pathology after aortic valve replacement using Hufnagel trileaflet prostheses: a study of 20 necropsy patients. Am Heart J 1975;89:443-448. 32. Roberts WC, Fishbein MC, Golden A. Cardiac pathology after valve reolacement bv disc orosthesis. A studv of 61 necroosv. d.oatients. Am J Cardiol i975;35:74fb760: 33. Roberts WC, Hammer WJ. Cardiac pathology after valve replacement with a tiltina disc orosthesis fBiork-Shilev tvoe). A studv of 46 necroosv oatients and 49Bjork-Shiley prdsiheses. Am j’Cardiol 1976;37:1024-1632. 34. Roberts WC. Choosing a substitute cardiac valve: type, size, surgeon. Am J Cardiol 1976: 38:633-644. 35. Spray TL, Roberts WC. Structural changes in porcine xenografts used as substitute cardiac valves. Gross and histologic observations in 51 glutaraldehyde-preserved Hancock valves in 41 patients. Am J Cardiol 1977; 40:319-330. 36. Ferrans VJ, Spray TL, Billingham ME, Roberts WC. Structural changes in alutaraldehvde-treated oorcine heteroarafts used as substitute cardiac vales. Transmission andscanning elect;on microscopic observations in 12 patients. Am J Cardiol 1978;41:1159-1184. 37. Geha AS, Laks H, Stansel HC Jr, Cornhill JF, Kilman JW, Buckley MJ, Roberts WC. Late failure of porcine valve heterografts in children. J Thorac Cardiovasc Surg 1979;78:351-364, 38. Wailer BF, Jones M, Roberts WC. Postoperative aortic regurgitation from incomplete seating of tilting-disc occluders due to overhandling knots or long sutures. Chest 1980;78:565-568. 39. Roberts WC. Comolications of cardiac valve reolacement: characteristic abnormalities of prostheses pertaining to any or specific site. Am Heart J 1982:103:113-122. 40. Roberts WC, tsner JM, Virmani R. Left ventricular incision midway between the mitral anulus and the stumps of the papillary muscles during mitral valve excision with or without rupture or aneurysmal formation: analysis of 10 necropsy patients. Am Heart J 1982;104: 1278-1287. 41. Warnes CA, Scott ML, Silver GM, Smith CW, Ferrans VJ, Roberts WC. Comparison of late degenerative changes in porcine bioprostheses in the mitral and aortic valve position in the same patient. Am J Cardiol 1983; 51:965-968. 42. Silver MA, Oranburg PR, Roberts WC. Severe mitral regurgitation immediately after mitral valve replacement with a parietal pericardial bovine bioprosthesis. Am J Cardiol 1983;52:218-219. 43. Warnes CA, McIntosh CL, Roberts WC. Wear of the metallic studs on the composite seat of the 2320 Starr-Edwards aortic valve and its clinical consequences. Am J Cardiol 1983;52:1062-1065. 44. Cohen SR, Silver MA, McIntosh CL, Roberts WC. Comparison of late (62 to 140 months) degenerative changes in simultaneously implanted and explanted porcine (Hancock) bioprostheses in the tricuspid and mitral valve ~ positions in six patients. Am J Cardiol 1984;53:1599-1602. 45. Ross EM, Roberts WC. A precaution when using the St. Jude Medical prosthesis in the aortic valve position. Am J Cardiol 1984;54:231-233. 46. Silver MA, Cohen SR, McIntosh CL, Cannon RO Ill, Roberts WC. Late (5 to 132 months) clinical and hemodynamic results after either tricuspid valve replacement or anuloplasty for Ebstein’s anomaly of the tricuspid valve. Am J Cardiol 1984;54:6271632. 47. Lester WM. Roberts WC. Fatal bioorosthetic reauraitation immedlatelv after mitral and tricuspid valve replacements with loge&-Shiley bioprostheses. Am J Cardiol 1985;55:590-592. 48. Roberts WC, Lachman AS. Mitral valve commissufofomy versus replacement. Considerations based on examination of operatively excised stenotic mitral valves. Am Heart J 1979;98:56-62. a good operation. Am J Cardiol 49. Roberts WC. Mitral commissurotomy-still 1983;52:A9-AIO.