Eur J Cardiothorac Surg 1999;15:3-11
© 1999 Elsevier Science NL
CarboMedics® Prosthetic Heart Valve 1
Joseph Craver*
Emory University Clinic, 1365 Clifton Road NE Suite 3119, Atlanta, GA 30322, USA
* Tel.: +-1-404-778-3480; fax: +1-404-778-4346.
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Abstract
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Introduction: The CarboMedics® Prosthetic Heart Valve has been in use since 1986, with more than 220 000 valves implanted through August of 1997 in more than 1550 centers in more than 100 countries. This paper presents the results of a multicenter, international clinical trial that has spanned 10 years. Methods: There were 1128 valves implanted in patients at 10 sites. The mean follow-up for patients was 4.5 years, with a total of 5110.0 patient-years. Approximately one-third of the patients came from the United States, one-third from Canada, and one-third from Scandinavia. The mean age was 57.2 years; 54.8% were men and 45.2% were women. The primary disease was calcification/atherosclerosis in 37% of the patients and rheumatic disease in 32.7%, and reoperation accounted for 17.5%. There were 556 aortic valve replacements, 428 mitral valve replacements, 139 double valve replacements, and 5 tricuspid replacements. Results: The survival rate of all implanted patients was 79% at 5 years postoperatively. The survival rate in redo valve patients was as good as the primary survival rate; the survival rate in double valve patients was not as good as the survival rate in single valve patients. There was no structural failure of the valve. Patient outcome as described by New York Heart Association class was significantly improved throughout the postoperative period. Rates of freedom from thrombosis, thromboembolism, and hemorrhage at 5 years were 98.9%, 90%, and 91%, respectively. Summary: Clinical results of the CarboMedics® Prosthetic Heart Valve in a midterm, multicenter study were excellent, with low rates of morbidity and mortality and no structural failure.
Key Words: CarboMedics® bileaflet mechanical valve • Mechanical heart valve prosthesis • Rotatable heart valve prosthesis • Valvular heart surgery
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1. Introduction
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I have had the privilege of participating in the CarboMedics® Prosthetic Heart Valve (CPHV) experience from its origin, as a member of the original pre-Food and Drug Administration trial group. Experience with the valve began with Jean-Yves Neveux in Paris, who performed the first implantation on December 18, 1986. The CPHV has had a remarkably successful and increasingly important role in the replacement valve arena, with more than 220 000 valves being implanted between September 1987 and August 1997 (Fig. 1
). The CPHV was the first high-quality rotatable bileaflet mechanical valve, and so it fit a need of the time, and when an innovation fits a pressing need, it is bound to be a success. The worldwide clinical experience with the CPHV over 11 years now includes over 1550 centers in more than 100 countries.
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2. Materials and methods
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The data I would like to relate to the 10-year experience in a clinical investigation that began in September 1987. Ten sites were involved; the enrollment period was from September 1987 to September 1993. There were 1128 valves implanted, comprised of 931 primary replacements and 197 replacements in patients with previous replacements. Patients had single, double, and triple valve replacements. Total patient follow-up was 5110.1 patient-years, with a mean follow-up of 4.5 years. Study population by country or region was 377 (33.4%) in the United States, 358 (31.7%) in Scandinavia, and 393 (34.8%) in Canada. There were 618 men (54.8%) and 510 women (45.2%). The mean age of 57.2 years was a little older than patients receiving prosthetic valves in general, but the range generally followed the distribution of patients having mechanical valve replacement (Fig. 2
). The population in the United States is certainly aging, and many of the older patients, 70 to 80 years old, receive tissue valves, but a number of patients in this age group still receive prosthetic valves.
Etiology of valve disease was calcification and atherosclerosis in 411 patients (37%), rheumatic heart disease in 369 (32.7%), failure of a previous prosthetic valve in 197 (17.5%), congenital anomalies in 137 (12.3%), infective endocarditis in 78 (6.9%), mitral chordae tendineae rupture or elongation in 44 (4%), and a variety of other causes with lesser contributions (each patient may have been in more than one etiology category). There were 556 aortic valve replacements (49.3%), 428 mitral valve replacements (37.9%), 139 double valve replacements (12.3%), and five tricuspid valve replacements (0.4%). Predominant valve sizes were in the usual adult ranges of 21–29 mm (Fig. 3
).
The Sulzer Carbomedics `Top HatTM' Supra-annular Aortic Valve (Fig. 4
) was not initially used in the trial but has significantly changed the practice in North America, where there is a large number of patients who have a significant discrepancy between the size of the aortic annulus and their body surface area. Its sewing ring adaptation allows the valve to sit completely above the annulus with the effective flow orifice over the entire outflow tract. This is particularly advantageous compared to an intraannular position, where part of the effective flow orifice is taken up by the housing and the sewing ring (Fig. 5
). A pledgeted or non-pledgeted non-everting mattress suture technique placed from the ventricular side up through the annulus and the sewing ring has been the recommended suture technique (Fig. 6
). The valve has been predominantly implanted in this manner. However, we and others (Craver JM, et al., pers. commun.) have experienced a problem with this technique whereby the tissue of the annulus is pulled into the flow orifice. This can reduce the effective orifice, as is seen in the valve in Fig. 7
. In an effort to eliminate this problem, more recently we now use a non-pledgeted figure-of-eight suture, beginning in an infraannular position (Fig. 8
). Fig. 9
shows these sutures all in place. When tied down, the encircled annular tissue is pulled both laterally and superiorly snugly under the sewing cuff. This is facilitated if the `aortic end' of the sutures is placed at the edge of the sewing ring and the `ventricular end' is placed centrally in the sewing ring (Fig. 10
). This technique pulls the annular tissue away from the flow orifice, so that no annular tissue can intrude or be pulled into the effective flow orifice. This modification in suture technique has significantly improved the situation and annular tissue can no longer be seen within the orifice area when the leaflets of the implanted valve are held open (Fig. 11
). The characteristics of the `Top Hat' model of the aortic valve in conjunction with our suture technique make it the valve of choice when there is disparity between body surface area and the size of the aortic annulus. One can virtually always move up one valve size and frequently move up two valve sizes. So a very significant increase in the effective flow orifice is possible, compared to what can be achieved with an intraannular valve.
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Fig. 5. The sewing ring adaptation of the `Top Hat' model of the CarboMedics® Prosthetic Heart Valve allows it to sit completely above the annulus and the effective flow orifice over the entire outflow tract.
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Fig. 6. A pledgeted or non-pledgeted non-everting mattress suture placed from the ventricular side up through the annulus and the sewing ring is the recommended suture technique.
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Fig. 11. No annular tissue can be seen intruding into the effective flow orifice when the valve leaflet is held open.
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3. Results
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The overall survival rate for all patients in the initial study with all CPHV valves was 79% at 5 years (Fig. 12
) with statistically significant numbers of patients up to 8 years. Survival rates by position of implantation were generally the same, although survival in double valve implantation was slightly lower, as would be expected (Fig. 13
). Data regarding primary versus previous valve replacement were notable (Fig. 14
). We rarely implant a mechanical valve as a reoperative valve of choice, except for the occasional mitral valve in a young patient, because the vast majority of patients in our reoperation population are older and therefore tend to receive tissue valves at reoperation. The survival rate was no different whether the procedure was a reoperation or a primary operation. The survival rate was almost 80% at 5 years in the reoperative patient group.
With the CPHV there was no structural valve failure in any positions (0% per patient-year). This compared to a rate of 0.0001–0.4160% per patient-year as reported in the Grunkemeier Historical Valve Review [1], which accumulated data from all prosthetic mechanical valves available at the time. It also compared to the 0% per patient-year as reported in an accumulated series of recent studies [2–12]with the St. Jude Medical valve (St. Jude Medical, Inc., St. Paul, MN), and to historical results [1]with the St. Jude Medical valve (0.0006% per patient-year). The CPHV results should reassure those who were concerned that the valve's rotatability would impair the long-term structural stability and durability of the pyrolyte carbon ring. In addition, incorporation of early unpublished European data on the new rotatable St. Jude Medical valve, which works differently and even has different early projections of durability, may adversely change their results. Although surgeons in the United States are following that situation closely and have begun looking cautiously at the rotatable St. Jude Medical valve on the basis of the European experience, the centers who prefer to use St. Jude Medical valves are often electing to use the standard rather than the newer rotatable models.
Results with the CPHV show significant improvement in patients' functional abilities as measured by the New York Heart Association (NYHA) classification, reflecting improvement in both activity and heart failure status (Fig. 15
). The change from 88.4% in NYHA class III or IV preoperatively to class I or II early is sustained up to 7 years postoperatively. Regarding freedom from valve-related morbidity and mortality, the cumulative data (Fig. 16
) demonstrate that at 5 years, 74.8% of patients are free from all instances of valve-related morbidity or mortality. This is an improvement over data in the Grunkemeier series and in the St. Jude Medical series.
There were 98 valve-related deaths: 12 from thromboembolism, four from thrombosis, 28 from hemorrhage related to Coumadin anticoagulation, 15 from endocarditis and 39 sudden or unknown death (Table 1
). Freedom from major hemorrhage at 5 years was 89.5% in aortic valve replacements, 94.5% in mitral valve replacements, and 86.8% in double valve replacements, for a total of 91% freedom from any major hemorrhagic complication (Fig. 17
). Freedom from significant perivalvular leak was also quite high (Fig. 18
). Paravalvular leak in bileaflet mechanical valves is difficult to assess, particularly with surface echocardiography, because there is a certain amount of regurgitational wash that can be overestimated very easily depending on the quality of both the echo techniques and the observer. The CPHV has a very surgeon-friendly sewing ring, and even relatively less experienced surgeons may find the CPHV easy to implant into a difficult calcified aortic annulus, especially in smaller patients.
Freedom from reoperation is presented in Fig. 19
. Explantation was required in 37 patients (3.3%). The causes were endocarditis in 7 patients (22.6%), perivalvular leak in 10 (32.3%), perivalvular leak with endocarditis in 4 (12.9%), upsizing in 1 (3.2%), pannus ingrowth in 2 (6.5%), stenosis because of intrusion by subvalvular tissue (probably due to a technical error) in 1 (3.2%), and thrombosis in 6 (19.4%). Valve failure requiring reoperation is occasionally seen in patients in whom there is impingement after partial or full resection of the native valve tissue. This can be a significant problem when trying to preserve much of the mitral apparatus. Fig. 20
shows leaflet entrapment by some of the retained chordal tissue in a St. Jude Medical valve; Aagaard has published a recent article describing how he imbricates the entire anterior and posterior leaflet with supraannular pledgeted sutures to eliminate this problem [13]. Our suture method has been to divide the anterior leaflet and fold it down and laterally to maintain the marginal chordae and the support from both anterior and posterior leaflets. Regardless of the method used, none of the elements left in the heart should be able to get through, impinge, or cause dysfunction of the prosthetic valve leaflets. This problem can be recognized with intraoperative transesophageal echocardiography, and if it occurs, which is rare, it can be repaired at the same time. The surgeon does not want this problem to be recognized late and require the patient to be reoperated acutely either after they have been transferred to the intensive care unit or after they have left the hospital.
The CPHV was 98.9% free from any incidence of thrombosis across all valves at 5 years (Fig. 21
). In summarizing the particularly critical issue of thrombosis, the 10-year experience with 1128 patients having aortic or mitral valve replacement with the CPHV had incidents of thrombosis – one aortic valve and ten mitral valves. These occurred from 10 days to 6 years postoperatively in ten women and one man, six of whom had not been adequately anticoagulated because of non-compliance or subtherapeutic anticoagulation levels up to 2400 patient-days. Three patients who experienced thrombosis were at therapeutic anticoagulation levels, and in two patients anticoagulation status was unknown.
There has been a great deal of discussion in the United States about the susceptibility of this valve to thrombosis. However, there are no data to say that there is any inherent problem upon review of all reports. The incidence of thromboembolism was higher, particularly in double valve replacement (Fig. 22
). This was probably related to the incidence of atrial fibrillation in the patients with long-standing and more severe disease. However, 90% freedom from significant incidents of thromboembolism for all CPHVs up to 8 years is excellent. Adequate anticoagulation levels remain a major problem in the United States; either the patients do not take the medication as directed or physicians do not prescribe it correctly or follow the patients carefully enough. Anticoagulation data were not available in 21 patients (32%) who experienced thrombosis or thromboembolism. Thrombosis or thromboembolism occurred in 6 patients (9.4%) in whom anticoagulation had not even been started. Poor patient compliance or anticoagulation interruption was present in 7 patients (10.9%) and subtherapeutic levels were documented in 18 (28.1%). Anticoagulation levels were therapeutic in only 12 patients (18.8%) in whom thrombosis or thromboembolism occurred. Therefore almost half of the patients who experienced thrombosis or thromboembolism were inadequately anticoagulated. Table 2
Table 3
compare the linearized rates of thrombosis and thromboembolism of the CPHV, the Grunkemeier data, and the St. Jude Medical valve. If patients are effectively anticoagulated and appropriately cared for by their physicians and adhere to the detailed regimen of medication, the CPHV works well and the patients do not experience thrombosis-related complications at levels any different than competing mechanical prosthetic valves.
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4. Summary
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These data demonstrate that the CPHV has excellent durability in both aortic and mitral positions. It has not been impaired by the advantages of its rotatability, thus making this valve the valve of choice for the last decade (Fig. 23
). The 10-year study demonstrated excellent results: 4.5 years of mean follow-up, with very low morbidity and mortality rates and no incidence of structural failure. The CPHV is a proven safe valve that in the study was rotated in situ in over 20% of patients. With a worldwide implantation record of 220 000 valves in many countries, these data indicate that this is a very good prosthetic heart valve with excellent results at 10 years postimplantation.
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Conference discussion
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Audience
: What about hemolysis after valve implantation?
Dr J. Craver
: There is virtually no incidence of significant hemolysis with the CPHV valve.
Audience
: Is there an increase in valve thrombosis when the mechanical valve is in the tricuspid position?
Dr J. Craver
: I would think so. Very few tricuspid valves are implanted, and we keep our patients in the hospital after tricuspid valve replacement until anticoagulation levels are clearly within range. I think we have just been lucky so far to have had no problem. I would think there would be a higher incidence of prosthetic valve thrombosis after tricuspid valve replacement due to slow flow on the venous side of the heart.
Dr M. Guida
(Valencia, Venezuela): What was your experience in the aortic position without anticoagulation?
Dr J. Craver
: We have not had any mechanical valves in adults that we have not anticoagulated. There have been a few children who have been managed with aspirin alone, but I would have to defer that to someone with a wider experience. If you do not anticoagulate these valves and they do not clot, you are simply lucky. Ours would all be anticoagulated with warfarin if possible, and with subcutaneous heparin if not.
Dr M. Benedetti
(Pisa, Italy): Would you anticoagulate a patient who has experienced a cerebral hemorrhage?
Dr J. Craver
: An aneurysm in the past or currently?
Dr M. Bendetti
: One who has experienced a cerebral hemorrhage during anticoagulant therapy.
Dr J. Craver
: As a complication?
Dr M. Bendetti
: Yes, as a complication.
Dr J. Craver
: It would depend on the status of the anticoagulation level at the time. If he experienced an intracerebral hemorrhage at a therapeutic level with an aortic valve, I would probably drop it to a lower level and anticoagulate him with aspirin as well as a lower dose of warfarin. If he was at an abnormally high level, I would bring it back to a more customary level and reanticoagulate after the hemorrhagic complication had cleared.
Dr G. Tolis
(Athens, Greece): How would you orient the valves in the aortic and the mitral positions?
Dr J. Craver
: We prefer to orient mitral valves in an antianatomic position, where both leaflets are subject to the same opening pressure. If you orient them in an anatomic position, the posterior leaflet may open but the anterior leaflet may not open fully, increasing the incidence of thrombosis due to stagnation around the anterior leaflet. In the aortic position, with a bileaflet valve it does not really matter. You should orient it so that valve leaflet motion is free of any impedance.
Dr H.H. Kure
(Aarhus, Denmark): What would you do with a thrombosed valve? Would you try to clear the thrombosis off the valve or would you immediately replace the valve?
Dr J. Craver
: Surgeons who are fortunate enough to operate on patients who are still alive with a thrombosed valve should probably replace the valve. The likelihood of being able to clear the valve in its current position, which led to a thrombosis, and get it all completely out is risky. We would advocate removing the valve and starting over, and probably being more careful with the anticoagulation protocol.
Audience
: Do you agree that pannus formation is not related to the type of valve? I think it is surgical technique or something else.
Dr J. Craver
: I think you are right. Pannus is more of a problem with late failure of the valve, where pannus has had time to grow. We have all operated on patients 20 years after valve replacement and seen pannus virtually encasing the valve. I am a little bit concerned about the `top hat' valve with regard to pannus because it is sitting above the annulus. But so far on annual follow-up echocardiograms we have not seen any encroachment or reduction in the outflow tract diameter, suggesting freedom from pannus at that point. So I am hoping that the velocity of flow in the aortic position will keep pannus from being a problem with the `top hat' valve. In the mitral position, where the valve sits solidly in the annulus, pulling the tissue back preserving the leaflets would move the pannus potential further away.
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Footnotes
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1 Presented at the Sulzer Carbomedics Sixth International Clinical Symposium, Copenhagen, Denmark, 27 September 1997. 
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References
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- Grunkemeier GL, Starr A, Rahimtoola SH. Prosthetic heart valve performance: long-term follow-up. Curr Problems Cardiol 1992;17:331-406.
- Kratz JM, Crawford FA, Sade RM, Crumbley AJ, Stroud MR. St. Jude prosthesis for aortic and mitral valve replacement: a ten-year experience. Ann Thorac Surg 1993;56:462-468.[Abstract]
- Fernandez J, Laub GW, Adkins MS, Anderson WA, Chen C, Bailey BM, Nealon LM, McGrath LB. Early and late-phase events after valve replacement with the St. Jude Medical prosthesis in 1200 patients. J Thorac Cardiovasc Surg 1994;107:394-407.[Abstract/Free Full Text]
- Horstkotte D, Schulte H, Bircks W, Strauer B. Unexpected findings concerning thromboembolic complications and anticoagulation after complete 10 year follow up of patients with St. Jude Medical prostheses. J Heart Valve Dis 1993;2:291-301.[Medline]
- Ibrahim M, O'Kane H, Cleland J, Gladstone D, Sarsam M, Patterson C. The St. Jude Medical prosthesis. J Thorac Cardiovasc Surg 1994;108:221-230.[Abstract/Free Full Text]
- Khan S, Chaux A, Matloff J, Blanche C, DeRobertis M, Kass R, Tsai TP, Trento A, Nessim S, Gray R, Czer L. The St. Jude Medical valve experience with 1000 cases. J Thorac Cardiovasc Surg 1994;108:1010-1020.[Abstract/Free Full Text]
- Baudet EM, Puel V, McBride JT, Grimaud JP, Roques F, Clerc F, Roques X, Laborde N. Long-term results of valve replacement with the St. Jude Medical prosthesis. J Thorac Cardiovasc Surg 1995;109:858-870.[Abstract]
- Nakano K, Koyanagi H, Hashimoto A, Kitamura M, Endo M, Nagashima M, Tokunaga H. Twelve years' experience with the St. Jude Medical valve prosthesis. Ann Thorac Surg 1994;57:697-703.[Abstract]
- Skudicky D, Essop MR, Wisenbaugh T, Skoularigis J, Essop AR, Dullabh A, Bedhesi S, Strugo V, Sareli P. Frequency of prosthetic valve-related complications with very low-level warfarin anticoagulation combined with dipyridamole after valve replacement using St. Jude Medical prostheses. Am J Cardiol 1994;74:1137-1141.[Medline]
- Jegaden O, Eker A, Delahaye F, Montagna P, Ossette J, Durand de Gevigney G, Mikaeloff PH. Thromboembolic risk and late survival after mitral valve replacement with the St. Jude Medical valve. Ann Thorac Surg 1994;58:1721-1728.[Abstract]
- Smith JA, Westlake GW, Mullerworth MH, Skillington PD, Tatoulis J. Excellent long-term results of cardiac valve replacement with the St. Jude Medical valve prosthesis. Circulation 1993;88:49-54.
- Isomura T, Hisatomi K, Hirano A, Kosuga K, Ohishi K. The St. Jude medical prosthesis in the mitral position. Eur J Cardio-thorac Surg 1994;8:11-14.[Abstract]
- Aagaard J, Andersen UL, Lerbjerg G, Andersen LI, Thomsen KK. Mitral valve replacement with total preservation of native valve and subvalvular apparatus. J Heart Valve Dis 1997;6:274-278.[Medline]
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Abstract
1. Introduction
