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Ann Thorac Surg 2001;71:S257-S260
© 2001 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, Royal Hospitals Trust, Belfast, Northern Ireland, United Kingdom
Address reprint requests to Mr O’Kane, Department of Cardiac Surgery, Royal Hospitals Trust, Grosvenor Rd, Belfast, Northern Ireland, BT12 6BA
e-mail: hugh{at}doctors.org.uk
Presented at the VIII International Symposium on Cardiac Bioprostheses, Cancun, Mexico, Nov 3–5, 2000.
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Abstract |
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Methods. Patients older than 70 years who had either a St. Jude Medical (SJM) mechanical prosthesis or any bioprosthesis (BP) implanted between January 1977 and December 1997 were identified. Alive patients were interviewed by telephone during a closing interval of 130 days.
Results. Complete follow-up was achieved with a total follow-up of 2,264 patient years. A total of 547 patients had 448 aortic valve replacements (199 SJM and 249 BP) and 99 had mitral valve replacements (76 SJM and 23 BP). A further 30 patients had double valve replacement. One hundred ninety of the 577 patients (33%) had coronary artery bypass grafting in addition to the valve replacement. Survival analysis showed no advantage for either mechanical or bioprosthetic valves. There was also no difference in thromboembolic rates, paravalvular leaks, structural dysfunction, and endocarditis rates. However, patients with mechanical valves had a significantly greater risk of major (p < 0.0001) and minor bleeding (p = 0.002) events.
Conclusions. Bioprosthetic valves do not offer a survival advantage over mechanical valves among the elderly. However, anticoagulant-related mortality and morbidity is statistically higher for patients with mechanical valves.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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A total of 607 valve prostheses were implanted: 326 mechanical (all St. Jude Medical [SJM] bileaflet prostheses; St. Jude Medical, St. Paul, MN) and 281 bioprostheses, of which 73 were stentless (St. Jude Medical SPV). The operative technique varied depending on the surgeon performing the procedure, but all surgeons used moderate hypothermia (28° to 32°C) along with either cold crystalloid or blood cardioplegia.
Patients with mechanical prostheses underwent anticoagulation with warfarin. The goal for the therapeutic range of the international normalized ratio was 2.0 to 3.0 and, more recently (1992 onwards), 2.0 to 2.5 for valves in the aortic position and 2.5 to 3.0 if a prosthesis was implanted in the mitral position. Patients with bioprostheses either underwent anticoagulation with warfarin for 3 months or were started on aspirin therapy. Until a therapeutic international normalized ratio was achieved in hospital, patients were maintained on either subcutaneous heparin or enoxaparin.
Follow-up for surviving patients was carried out by telephone interview with the patient, their family physician, or a close relative during a closing interval of 130 days. Data for deceased patients were obtained from hospital and family physicians’ records as well as from death certificates obtained from the Statistics and Research Agency of Northern Ireland. We adhered to the guidelines of the Society of Thoracic Surgeons [4] for reporting morbidity and mortality after cardiac valvular operations. Follow-up was 100% complete.
Statistical analysis
For univariate comparisons the 
2 test and Fisher’s exact probability test were used. The Kaplan–Meier method was used for actuarial analysis, applying either Breslow’s or log-rank significance tests. The Statistica software package (Statsoft Inc, Tulsa, OK) was used with an IBM PC compatible desktop computer.
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Results |
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Of the 577 patients, 230 (39.8%) underwent additional procedures along with the valve replacement. These procedures included coronary artery bypass grafting (190, 33%), valve repair (23, 4%), septal myectomy (9, 1.5%), and others (8, 1.4%).
In-hospital and 30-day mortality
Twenty-five patients (4.3%) died either in hospital or in the first 30 days (range 0 to 35 days). Of these 25, 2 patients had undergone mechanical DVR and 23 had undergone single valve replacement. Six patients died after mechanical MVR (7.9%), 2 after bioprosthetic MVR (8.7%), 10 after mechanical AVR (5.0%), and 5 after bioprosthetic AVR (2.0%).
Of the 25 early deaths, 6 were inpatients undergoing reoperative procedures. Thus the reoperative mortality was 11.1% (6 of 54 patients).
Late mortality
One hundred thirty-six patients (23.6%) died during the follow-up period. The causes of death are listed in Table 1.
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Actuarial analysis
Four hundred sixteen patients were alive at follow-up to give a total follow-up of 2,264 patient-years. The actuarial survival for bioprostheses and mechanical valves is shown in Figure 1. Survival curves for the various types of aortic prostheses are shown in Figure 2. We calculated the 50% cumulative proportion surviving to be 6.1 years for all MVRs and 10.4 years for all AVRs (p = 0.0002). The 50% cumulative proportion surviving for all bioprostheses was 9.9 years and for all mechanical prostheses was 9.1 years (p = NS). The 50% cumulative proportion surviving for stented bioprostheses in the aortic position was 10.7 years and for mechanical prostheses in the aortic position was 9.8 years (p = NS).
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Among patients who had mechanical prostheses, we documented 30 major bleeding events, 46 minor bleeding events, and 75 episodes of thromboembolism. Among patients with bioprostheses, there were significantly fewer major bleeding events (6 events, p < 0.0001) and minor bleeding events (24 events, p = 0.02), but there was no significant difference in the thromboembolic events (79 events, p = 0.32).
Valve-related mortality
We documented 41 deaths as valve related, including 3 patients with DVR (2 with mechanical DVRs and 1 with a bioprosthetic DVR). Of the 9 MVR-related deaths, 7 patients had mechanical MVRs and 2 had bioprosthetic MVRs. Of the 29 AVR-related deaths, 17 patients had mechanical AVRs and 12 had bioprosthetic AVRs.
Intracerebral bleeding led to 7 deaths in the mechanical AVR group, 2 deaths in the mechanical MVR group, and 1 death in the mechanical DVR group. There was only 1 death due to intracerebral bleeding in the bioprosthetic group, in a patient with a stented AVR. Hemorrhage, other than intracerebral, accounted for 3 deaths in the mechanical AVRs, 2 deaths in the mechanical MVRs, and 2 deaths in the bioprosthetic AVRs.
There were 6 deaths from thromboembolic CVA in the mechanical AVRs, 4 in the bioprosthetic AVRs, 4 in the mechanical MVRs, 2 in the bioprosthetic MVRs, and 1 death each for the mechanical and bioprosthetic DVRs.
Five patients died with endocarditis: 2 had stentless AVRs, 2 had stented AVRs, and 1 had a mechanical AVR. We could attribute only 1 death to structural dysfunction, in a patient whose stented aortic bioprosthesis had become grossly incompetent 10.5 years after implantation.
Prosthetic valve endocarditis
Eight patients had endocarditis during the follow-up period. The 5 who died are detailed above. Six had undergone bioprosthetic AVR (3 stented, 3 stentless) and 2 mechanical AVR. One patient had presented with prosthetic valve endocarditis (previous stentless bioprosthesis and fungal endocarditis). He had a mechanical prosthesis implanted at the time of his redo operation but succumbed to endocarditis of the new valve prosthesis. Another patient had to have a stentless bioprosthesis explanted during the follow-up period that was replaced successfully with a mechanical prosthesis. Although there was no statistical difference between the mechanical and bioprosthetic groups (p = 0.09), the trend was toward a higher incidence of endocarditis in the bioprosthetic group.
Structural dysfunction
One patient with a stented bioprosthetic AVR was being conservatively managed for valve incompetence 8 years after the replacement. No mechanical prostheses malfunctioned.
Periprosthetic leak
Five patients had periprosthetic leaks. Of these, 2 had undergone bioprosthetic MVR and 2 had undergone mechanical MVR; all four were repaired. The fifth patient with a stentless bioprosthetic AVR developed a leak and was being followed conservatively.
Prosthetic valve hemolysis
Two patients had hemolysis; 1 patient with a mechanical MVR and who did not have a periprosthetic leak was treated satisfactorily with oral iron supplements. Another patient who had a periprosthetic leak after bioprosthetic MVR had a successful repair of the leak.
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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Surprisingly, we found that 51 of 194 patients (26%) alive after bioprosthetic AVRs were on long-term warfarin. Patients are increasingly prescribed warfarin for indications other than valve replacement. Some of our patients with bioprosthetic valves were in atrial fibrillation and others had been prescribed warfarin for transient ischemic attacks.
Because of the significantly higher anticoagulation-related complications demonstrated in this study, we would tend to favor bioprosthetic valves in the aortic position for patients older than 70 years of age who are in sinus rhythm. Our experience with stentless aortic valves is not sufficient to make a definitive statement; however, our early survival data are encouraging and in agreement with other authors [6].
We did not show an overall survival advantage for the bioprosthesis group; this finding may be related to other factors such as undetected or untreated bioprosthetic valve dysfunction, possibly because the elderly patient may not be investigated as aggressively as younger patients.
There is an increasing interest in improving anticoagulation control using more frequent monitoring, computerized decision support [7], and, more recently, self-managed anticoagulation [8, 9]. Additionally, lower anticoagulation ranges are recommended [10] and the combination of these factors may result in a reduction of anticoagulation-related complications. By addressing this problem of anticoagulation-related hemorrhage and reducing it by these various methods the main advantage of the bioprosthetic valve may be negated. Further studies will then be required to decide whether a survival advantage may result from using mechanical prostheses for the elderly patient.
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References |
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