Mitroflow Synergy Prostheses for Aortic Valve Replacement: 19 Years Experience With 1,516 Patients

Mitroflow Synergy Prostheses for Aortic Valve Replacement: 19 Years Experience With 1,516 Patients Kazutomo Minami, MD, Armin Zittermann, PhD, Sebastian Schulte-Eistrup, MD, Heinrich Koertke, MD, and Reiner Körfer, MD Department of Cardiothoracic Surgery, Heart Center Northrhine-Westfalia, Ruhr University of Bochum, Bad Oeynhausen, Germany Background. Pericardial prostheses have been used as valvular substitutes since 1975. They combine excellent hemodynamic characteristics with a low risk of valve failure during long-term observation. The aim of this article is to describe the clinical long-term performance of the Mitroflow Synergy pericardial valve (Sorin Group Inc, Mitroflow Division, Vancouver, Canada) in the aortic position for as long as 19 years. Methods. Data were obtained between February 1985 and April 2004 from patients with aortic heart valve replacements (n 1,464) or from patients with replacements of existing prosthetic aortic valves (n 52). The age group distributions are less than 70 years (n 175); 70 to 74 years (n 462); 75 to 79 years (n 532); 80 to 84 years (n 273); and greater than or equal to 85 years (n 74). The cause of the aortic valve lesions was combined (insufficiency and stenosis) in the majority of patients (62.4%). Concomitant procedures were performed in 897 patients (59.2%) and coronary artery bypass grafting was the most common (53.5%). Mean follow-up was 5.5 0.09 years. Total follow-up was 8,408 patient-years. Results. The early mortality (30 days) was 6.6% (n 99) and late deaths were 60.8% (n 921). Actuarial event-free rates at 5, 10, and 15 years of follow-up are given as mean standard error for endocarditis: 96.9 0.5, 92.8 1.2, and 92.0 1.4, respectively; embolism: 96.7 0.6, 88.8 1.7, and 82.9 3.5, respectively; bleeding: 98.5 0.4, 97.2 0.6, and 94.4 1.7, respectively; structural valve deterioration: 99.0 0.3, 82.8 2.2, and 62.8 5.8, respectively; and reoperation: 98.2 0.4, 79.2 2.4, and 63.4 5.3, respectively. The rate of endocarditis, structural valve degeneration, and reoperation was lower in patients 75 years of age and older compared with younger patients, whereas embolism occurred more frequently in elderly than in younger patients. Conclusions. Adverse events after implantation of Mitroflow aortic bioprosthesis rarely occurred during the first 5 years after valve replacement. The results of the prosthesis indicates reliable long-term morbidity rates and good durability in patients 75 years of age and older. (Ann Thorac Surg 2005;80:1699 705) 2005 by The Society of Thoracic Surgeons The Mitroflow pericardial valve bioprosthesis (Sorin Group Inc, Mitroflow Division, Vancouver, Canada) was introduced into clinical use in 1982. This is a second generation bioprosthesis made of a single sheet of glutaraldehyde-preserved bovine pericardium mounted on the outside of a flexible Dacron-covered Delrin stent. Due to its design characteristics, an unimpeded leaflet opening and blood flow occurs, which results in an excellent hemodynamic performance [1 4] and a proven superiority when compared with other pericardial bioprostheses [5]. Extensive clinical results of aortic valve replacement with the Mitroflow pericardial bioprosthesis have been performed [6 13]. These studies recommended the implantation of such bioprosthesis in patients older than 70 years of age. Accepted for publication April 27, 2005. Address correspondence to Dr Minami, Department of Cardiothoracic Surgery, Heart Center NRW, University of Bochum, Georgstrasse 11, Bad Oeynhausen, 32545 Germany; e-mail: kminami@hdz-nrw.de. We have been using this valve for aortic replacement since 1985, especially for the application in the small aortic annulus. We have already reported long-term durability and superior hemodynamics of the bioprosthesis at 7-year and 12-year follow-ups [14, 15]. The aim of this article is to report the clinical results of 19 years experience with an extended patient population. Material and Methods Patients This retrospective report summarizes data obtained between February 1985 and April 2004 from patients with an aortic heart valve replacement at the Heart Center North Rhine Westfalia in Bad Oeynhausen, Germany. We included only those patients who had a Mitroflow Synergy valve implantation through November 1999 in our data analysis in order to achieve a sufficient follow-up period. A total of 1,516 patients with a mean age at implant of 75.6 years (range, 16 to 92 years) were 2005 by The Society of Thoracic Surgeons 0003-4975/05/$30.00 Published by Elsevier Inc doi:10.1016/j.athoracsur.2005.04.053

1700 MINAMI ET AL Ann Thorac Surg MITROFLOW SYNERGY PROSTHESES FOR AORTIC VALVE REPLACEMENT 2005;80:1699 705 included in our data analysis. Inclusion criteria were an aortic valve replacement (n 1,464) or a replacement of an existing prosthetic aortic valve (reoperations, n 52). We also included patients with active endocarditis at the time of implant in this report (n 9). Standard operative procedures were applied for aortotomy and valve removal using crystalloid cardioplegia solution (Custodiol HTK, Koehler Chemie GmbH, Alsbach-Hahnlein, Germany). The implantation technique for the Mitroflow Synergy bioprosthesis was similar to those of other aortic bioprostheses with single mattress sutures. ages as follows: less than 70 years, 70 to 74 years, 75 to 79 years, 80 to 84 years, and greater than or equal to 85 years. The log-rank test was used to test for differences in complication rates and survival rates of specific subgroups. A p value 0.05 was considered statistically significant. The risks of adverse events (ie, deaths or morbid events that occurred postoperatively) were estimated using linearized rates (percent per patient-year). They were calculated as the number of late events divided by the cumulative late postoperative patientyears (pt-yrs) and were expressed as a percentage. Study Valve The Mitroflow Synergy valve is a bioprosthetic heart valve consisting of bovine pericardium leaflets that are glutaraldehyde treated and mounted around a flexible stent. From February 1985 until July 1992, the patients were provided with valve type 11 (n 497). In May 1992, we started to use valve type 12 (n 1,024). Valve size distribution was 19 mm (n 192), 21 mm (n 629), 23 mm (n 605), 25 mm (n 78), and 27 mm (n 12). Methods We used the computer program FileMaker Pro 4 to assess the preoperative, intraoperative, and postoperative raw data. We retrospectively assessed all adverse events related to the heart valve prosthesis, such as bleeding, endocarditis, embolism, leak, tear, valve degeneration, and explantation that occurred during the follow-up interval. Adverse events were classified based on the Food and Drug Administration s Heart Valve Guidance [16], The Society of Thoracic Surgeons and the American Association of Thoracic Surgeons Guidelines for Reporting Mortality and Morbidity after Cardiac Valvular Operations [17], and the Proposal for Reporting Thrombosis, Embolism, and Bleeding after Heart Valve Replacement [18]. Every 2 years, we called the patients by telephone in order to assess New York Heart Association (NYHA) functional class and survival. In those patients who had died during the follow-up period, we requested the medical report from the general practitioner or emergency hospital to determine the cause of death. Causes of death were classified into those with evidence of valverelated causes, such as endocarditis or valve degeneration; potentially valve-related causes, such as stroke and sudden death; cardiovascular-related causes, such as heart failure, myocardial infarction, and cardiac arrest; and other causes, such as renal failure, lung failure, diabetes mellitus, infection, neoplasm, and unknown causes. Statistics Statistical evaluations were performed with the Statistical Package for Social Sciences, version 11 (SPSS, Inc, Chicago, IL). Categorical variables were reported using the number (n) and percent of observations. Continuous variables were expressed as mean values with standard error. Complication rates and survival rates were calculated with the Kaplan-Meier product-limit estimator. For data analysis, patients were grouped according to their Results The baseline and clinical characteristics of the patients are given in Table 1. The majority of patients were female (70.2%). Moreover, most of the patients were aged 70 years or older. The cause of the aortic valve lesions was mixed in the majority of patients, whereas only 33.8% had aortic insufficiency and 3.8 % had only aortic stenosis. A large number of patients had concomitant diagnoses such as hypertension (50.9%), coronary artery disease (48.2%) with myocardial infarction (15.0%), diabetes mellitus (20.5%), renal failure (13.5%), and cerebrovascular disease with a history of stroke (3.9%). Of the 1,516 patients, 897 underwent concomitant surgical procedures (Table 1). Coronary aortic bypass grafting was the most Table 1. Baseline Characteristics of the Patients at Enrollment (n 1,516) Parameter Number Percent Gender Male 452 29.8 Female 1,064 70.2 Age (y) 70 175 11.5 70 74 462 30.5 75 79 532 35.1 80 84 273 18.0 85 74 4.9 Aortic Lesion Stenosis 58 3.8 Insufficiency 513 33.8 Mixed 945 62.4 Concomitant Diagnoses Stroke 59 3.9 Diabetes mellitus 310 20.5 Myocardial infarction 227 15.0 Coronary heart disease 731 48.2 Renal insufficiency 205 13.5 Hypertension 772 50.9 Concomitant procedures Coronary artery bypass grafting 811 53.5 Intraaortic ballon pumping 21 1.4 Ventricular assist device 9 0.6 Mitral valve replacement 56 3.7

Ann Thorac Surg MINAMI ET AL 2005;80:1699 705 MITROFLOW SYNERGY PROSTHESES FOR AORTIC VALVE REPLACEMENT Table 2. Mortality and Survival Estimates Causes of Death Survival (%) 1701 Operative Period 30 Days 1 Year 2 Year 5 Year 10 Year 15 Year All causes 93.6 87.4 82.5 64.5 24.5 5.5 Evident valve related 100 99.2 98.1 95.1 83.7 76.7 Potentially valve related 99.6 98.2 97.8 93.9 85.1 82.0 Cardiovascular related 96.61 94.53 93.1 88.5 68.7 42.1 Others 97.9 93.9 90.4 75.2 38.1 19.8 Unknown 97.2 95.8 94.6 87.2 58.1 27.9 frequently performed concomitant procedure. Fifty-six patients had an additional mitral valve replacement. The average follow-up period was 5.5 0.09 years (range, 0.0 to 19.3 years). In total, the 1,516 patients accrued 8,408 pt-yrs of observation. As of database closure, 1,320 patients had completed 1 year of follow-up, 759 patients had completed 5 years of follow-up, 138 had completed 10 years of follow-up, and 11 had achieved 15 years of follow-up. Forty-five patients (2.97%) were considered lost to follow-up. No intraoperative deaths occurred. Ninety-nine deaths (6.56%) occurred within 30-days of valve replacement. None of these patients died because of evident valverelated complication. Six causes were potentially vale related (stroke, n 4; sudden death, n 2). Fifty five deaths were cardiovascular related (cardiac decompensation, n 42; myocardial infarction, n 13) and 16 deaths were caused by other reasons (gastrointestinal failure, n 8; multiple organ failure, n 5; infections, n 3). Twenty-two causes of death were unknown. Nine hundred and twenty-one late deaths were reported during the follow-up (60.8% of all patients). Forty-six deaths (5.0%) were classified as evident valve-related causes, 267 deaths (28.8%) had cardiovascular-related causes, 304 deaths (33.0%) were classified as others including 108 potentially valve-related deaths that had occurred (11.75%; 27 sudden deaths and 81 cases of stroke), whereas in 196 deaths (21.3%) the causes were unknown. When all-cause mortality is considered, overall survivals at 1 year and at 5 years were 87.4% and 64.5%, respectively. Table 2 reports the freedom from all-cause mortality and evident valve-related mortality by different follow-up period. Evident valve-related mortality was less than 5% within 5 years of aortic valve replacement and less than 20% within 10 years of valve replacement. In patients who were younger than 70 years, the risk of evident valve-related death began to increase 5 years after valve implantation compared with patients who were 70 years and older (Fig 1). However, in the patient groups aged 70 to 75 years and more than 75 years, the course of the survival curves was very similar during the first 10 years after valve implantation. Functional improvement of the implant patients was documented by a marked decrease in NYHA classification. Preoperatively, 1,359 patients (89.6%) of the entire cohort were in either class III or IV; 135 (8.9%) were in class II, and 22 (1.5%) were in class I. Postoperative NYHA classification was available from 778 patients. The last NYHA assessment was performed at a mean time of 6.0 2.9 years after implant. At that time, 288 patients (37.0%) were in class I, 344 (44.2%) in class II, 121 (15.6%) in class III, and 25 (3.2%) in class IV. In our cohort of 1,516 patients, 393 clinically significant valve-related adverse events occurred. In detail, 26 patients developed a bleeding event (0.3% per pt-yrs); embolism was diagnosed in 68 patients (0.8% per pt-yrs); endocarditis occurred in 52 patients (0.6% per pt-yr); and 29 additional patients had a paravalvular leakage (0.3% per pt-yr). Among these patients, 84 had a structural valve deterioration. A subset of 33 patients of these 84 with structural valve deterioration developed a tear (0.4% per pt-yrs). The valve was explanted in 101 patients. Of these 101 patients, 11 patients died within 30 days of explantation. Four deaths were classified as evident valve-related causes, 4 as cardiovascular-related causes, 2 as other causes, and 1 as an unknown cause. In 251 patients, more than one valve-related complica- Fig 1. Long-term Kaplan-Meier survival estimates for evident valverelated death in patients with Mitroflow Synergy aortic bioprostheses according to patient age.

1702 MINAMI ET AL Ann Thorac Surg MITROFLOW SYNERGY PROSTHESES FOR AORTIC VALVE REPLACEMENT 2005;80:1699 705 tion was observed. Most frequently, a bleeding complication occurred in combination with embolism (n 60). Moreover, the bioprosthesis had to be explanted because of valve degeneration in 51 patients and because of a tear in 28 patients. In 1,265 patients (83.4%), no valve-related complication occurred during the follow-up period. Of these 1,265 patients, 758 patients died during the observation period so that they definitively did not experience a valve-related complication. Endocarditis, embolism, valve degeneration, tear, and explantation were all significantly associated with age (Fig 2). However, although endocarditis, valve degeneration, tear, and explants were less frequent in elderly patients when compared with younger patients, embolism occurred more often in the elderly patients than in the younger ones. Bleeding events, occurrence of a leak, and myocardial infarction were seen not to be age related (data not shown; p values 0.466 to 0.824). Adverse events were rarely seen within the first 5 years of valve replacement (Table 3). Thereafter, especially structural valve deterioration began to increase. After 15 years of follow-up, 4 of the remaining 11 patients with bioprostheses showed structural deterioration. In parallel with the increase in valve degeneration after a follow-up period of 5 years, the percentage of explants began to increase after that time, too. We have also performed separate statistical analysis for the valve types 11 and 12. Our data analysis showed similar age-dependent trends in complication rates for the two models (data not shown). Anticoagulation was performed with coumarin derivatives from the second day to as many as 6 weeks or as many as 3 months in the case of sinus rhythm. Thereafter, anticoagulation was usually stopped. During the follow-up period, antithrombotic therapy was reported for only 7 patients. These patients received coumarin derivatives in a dose that allowed them to achieve an international normalized ratio target range of 2.0 to 3.0. We did not treat this cohort of patients with platelet aggregation inhibitors. Comment This report demonstrates that the Mitroflow bioprosthesis shows reliable durability and low long-term morbidity. Considering the mean age of the study population of 75.6 years, the 5-year survival of 64.5% of our cohort of patients is a good result. If one computes the relative survival of the Mitroflow patients compared with the general life expectancy of 75-, 80-, and 85-year-old male and female Germans, the ratios are 0.52 to 0.69 for female patients and 0.58 to 0.91 for male patients [19]. Despite these relatively low ratios, it should be mentioned that evident valve-related deaths only contributed 5% to the total number of deaths. Relatively few deaths occurred from potentially valve-related events such as sudden death (3%). Moreover, the potentially valve-related event of lethal stroke (8.8%) may have had various other reasons. It is noteworthy that in 1998 stroke was identified as the cause of death for 4.25% of all Germans who died between the ages of 65 and 75 years and for 8.37% of all patients who were older than 75 when they died [20]. These data indicate that in our cohort the majority of deaths caused by stroke may not be related to the Mitroflow bioprosthesis. Compared with mechanical heart valves, bioprostheses have the advantage of not requiring anticoagulation, but the disadvantage of more frequent structural valve degeneration. There is evidence from recently performed studies that implantation of bioprostheses can induce a xenograft-specific immune response. However, the immune response against bioprostheses may be reduced and durability may be extended by procedures that diminish the presence of immunologically relevant molecules [21]. The results presented of 19 years experience with a large number of patients support earlier recommendations to implant the Mitroflow bioprosthesis only in elderly patients [6 13]. Figures 2A 2E indicate that implantations should be rigorously restricted to patients older than 75 years. This recommendation is based on the finding that especially in patients who are younger than 75 years of age, the probability of freedom from endocarditis, tear, and valve degeneration is only high during the first 5 years after valve implantation, and the risk of valve explantation increases after that time. Moreover, in elderly patients the probability of valve degeneration, endocarditis, and tear remains relatively low during the second 5 years after valve implantation. The agerelated differences in complication rates may be due to the fact that younger patients are more physically active and exert more stress on the pericardial tissue. Also as shown by our results, a high percentage of the patients who are older than 75 years of age will have died because of non valve-related reasons before a valve-related event occurs. It is well known that embolism is a serious complication in elderly subjects, even in those patients without biological heart valve prostheses. This may be due to hypertension, atrial fibrillation, and at least in part to an increased risk of dehydration caused by agerelated changes in kidney function, thirst perception, body water content, and homeostatic capacity [22]. Figure 2B indicates that the risk of embolism after valve implantation is highest in the patients who are older than 85 years of age. However, it is noteworthy that a high proportion of subjects in this age group (27%) also usually report drinking amounts of less than 1 liter [22]. It has also been shown that the proportion of 27% of the very old patients is markedly higher compared with younger patients (75 to 84 years, 15%; 65 to 74 years, 8%) [22]. In our study the probability of freedom from embolism is very high in patients who are younger than 70 years of age during the first years after valve implantation. In contrast, the risk of an embolic event already begins to increase during the first years after valve implantation in the patients who are older than 75 years of age and older than 80 years of age (Fig 2B). Data indicate that the risk of embolism may be more related to age than to the implantation of

Ann Thorac Surg MINAMI ET AL 2005;80:1699 705 MITROFLOW SYNERGY PROSTHESES FOR AORTIC VALVE REPLACEMENT 1703 Fig 2. Occurrence of valve-related complications according to patient age: (A) endocarditis, (B) embolism, (C) tear, (D) structural valve degeneration, and (E) valve explantation.

1704 MINAMI ET AL Ann Thorac Surg MITROFLOW SYNERGY PROSTHESES FOR AORTIC VALVE REPLACEMENT 2005;80:1699 705 Table 3. Patient Morbidity and Freedom From Adverse Events Adverse Event Freedom from Event (%) Number Operative Period 30 Days 1 Year 2 Year 5 Year 10 Year 15 Year Endocarditis 52 100 99.5 98.9 96.9 92.8 92.0 Embolism 68 100 99.5 99.2 96.7 88.8 82.9 Bleeding 26 100 100 99.6 98.5 97.2 94.4 Valve leak 29 100 99.9 99.9 99.1 98.2 96.1 Valve tear a 33 100 100 100 99.9 92.3 82.7 Structural valve deterioration 84 100 100 100 99.0 82.8 62.8 Explant 101 99.1 99.7 99.5 98.2 79.2 63.4 a Tear is a subset of structural valve deterioration events. the bioprosthesis. Similarly with an increased risk of body dehydration, the risk of embolism obviously begins to increase when a critical age of approximately 77 to 80 years is reached. The observed relations argue for the possibility to improve drinking behavior by selective educational measures and to recommend platelet inhibitors after valve implantation. The number of patients who received bioprostheses with valve sizes less than or equal to 25 mm was relatively small. Because of geometric reasons, the 10-year freedom from structural valve degeneration is approximately 30% lower in the Mitroflow bioprosthesis with valve sizes greater than or equal to 25 mm compared with valve sizes less than 25 mm [15]; we have implanted only very few such bioprostheses during the last 10 years. The use of the Mitroflow bioprosthesis, especially for patients with small annuli also explains the reason for the relatively high percentage of female patients in our study cohort. In patients with larger annuli (eg, in a significant number of male patients), we implanted the Hancock bioprothesis (Medtronic Inc, Minneapolis, MN). This study has some limitations. Follow-up was retrospectively performed, NYHA functional class was obtained by telephone interview, and clinical outcomes such as morbidity and mortality were obtained by review of death reports filled out by personnel. This may have limited the detection of valve-related pathology. Moreover, structural valve failure was detected only if a patient required reoperation. Patients who did not undergo reoperation, despite having structural valve failure, have not been included. This could have resulted in an underestimation of the rate of structural valve deterioration. In summary, the Mitroflow bioprosthesis is a reliable choice when an aortic heart valve is required, especially in patients over 75 years of age who have a small aortic annulus. References 1. Gonzales-Juanatey JR, Acuna JM, Amaro A, et al. Doppler echocardiographic comparison of small (19 mm) bileaflet and pericardial heart valve prostheses in the aortic position. Scand J Thorac Cardiovasc Surg 1995;29:29 35. 2. Reichenspurner H, Weinhold C, Nollert G, et al. Comparison of porcine biological valves with pericardial valves a 12-year clinical experience with 1123 bio-prostheses. Thorac Cardiovasc Surg 1995;43(1):19 26. 3. Reul H, Giersiepen M, Schindehutte H, Effert S, Rau G. Comparative in vitro evaluation of porcine and pericardial bioprostheses. Z Kardiolol 1986;75(Suppl 2):223 31. 4. Minami K, Schereika S, Kortke H, Gleichmann U, Korfer R. Long term follow-up of Mitroflow pericardial valve prostheses in the small aortic annulus. J Cardiovasc Surg (Torino) 1993;34(3):189 93. 5. Pelletier LC, Carrier M. In: Acar J, Bodnar E, eds. Textbook of acquired heart valve disease, vol II. London: ICR Publishers, 1995:513 21. 6. Loisance D, Zouari M, Leandri J, Hillion ML, Cachera JP. The Mitroflow pericardial valve. First five years of follow-up evaluation. ASAIO Trans 1989;35(3):304 7. 7. Loisance DY, Mazzucotelli JP, Bertrand PC, Deleuze PH, Cachera JP. Mitroflow pericardial valve: long-term durability. Ann Thorac Surg 1993;56(1):131 6. 8. Moggio RA, Pooley RW, Sarabu MR, Christiana J, Ho AW, Reed GE. Experience with the Mitroflow aortic bioprosthesis. J Thorac Cardiovasc Surg 1994;108(2):215 20. 9. Pomar JL, Jamieson WR, Pelletier LC, Gerein AN, Castella M, Brownlee RT. Mitroflow pericardial bioprosthesis: clinical performance to ten years. Ann Thorac Surg 1995;60 (Suppl 2):S305 9; discussion S309-10. 10. Pomar JL, Jamieson WR, Pelletier LC, Castella M, Germann E, Brownlee RT. Mitroflow pericardial bioprosthesis experience in aortic valve replacement or 60 years of age. Ann Thorac Surg 1998;66(Suppl 6):S53 6. 11. Reber D, Birnbaum DE, Tollenaere P, Eschenbruch E. Long-term results after aortic valve replacement with the Mitroflow pericardial valve. J Cardiovasc Surg 1996; 37(Suppl 1):23 7. 12. Thulin LI, Thilen UJ, Kymle KA. Mitroflow pericardial bioprosthesis in the aortic position. Low incidence of structural valve deterioration in elderly patients during an 11-year follow-up. Scand Cardiovasc J 2000;34(2):192 6. 13. Mazzucotelli JP, Bertrand PC, Loisance DY. Durability of the Mitroflow pericardial valve at ten years. Ann Thorac Surg 1995;60 (Suppl 2):S303 4. 14. Minami K, Schereika S, Kortke H, Gleichmann U, Korfer R. Long term follow-up of Mitroflow pericardial valve prostheses in the small aortic annulus. J Cardiovasc Surg 1993;34(3): 189 93. 15. Minami K, Boethig D, Mirow N, et al. Mitroflow pericardial valve prosthesis in the aortic position: an analysis of longterm outcome and prognostic factors. J Heart Valve Dis 2000;9(1):112 22.

Ann Thorac Surg MINAMI ET AL 2005;80:1699 705 MITROFLOW SYNERGY PROSTHESES FOR AORTIC VALVE REPLACEMENT 16. Johnson DM, Sapirstein W. FDA s requirements for in-vivo performance data for prosthetic heart valves. J Heart Valve Dis 2000;3:350 5. 17. Edmunds LH Jr, Clark RE, Cohn LH, Grunkemeier GL, Miller DC, Weisel RD. Guidelines for reporting morbidity and mortality after cardiac valvular operations. Ad Hoc Liaison Committee for Standardizing Definitions of Prosthetic Heart Valve Morbidity of The American Association for Thoracic Surgery and The Society of Thoracic Surgeons. J Thorac Cardiovasc Surg 1996;112: 708 11. 18. Bodnar E, Butchart EG, Bamford J, Besselaar AM, Grunkemeier GL, Frater RW. Proposal for reporting thrombosis, 1705 embolism and bleeding after heart valve replacement. J Heart Valve Dis 1994;3:120 3. 19. Federal Statistical Office. Statistical Yearbook. Metzler- Poeschel Wiesbaden, Germany, 2000, 424-5. 20. Federal Statistical Office. Statistical Yearbook. Metzler- Poeschel Wiesbaden, Germany, 2004, 54. 21. Konakci KZ, Bohle B, Blumer R, et al. Alpha-gal on bioprostheses: xenograft immune response in cardiac surgery. Eur J Clin Invest. 2005;35:17-3. 22. Volkert D, Kreuel K, Stehle P. Nutrition beyond 65-Amount of usual drinking fluid and motivation to drink are interrelated in community-living, independent elderly people. Z Gerontol Geriatr 2004;37:436 43 [in German]. INVITED COMMENTARY The authors [1] are to be commended for their careful study of a large cohort of predominantly elderly patients who underwent aortic valve replacement with a Mitroflow Synergy pericardial prosthesis (Sorin Group Inc, Mitroflow Division, Vancouver, Canada). They conclude that the bioprosthesis is a reliable choice, especially in patients older than 75 years of age with a small aortic annulus. Previously published reports suggest that structural valve deterioration of this prosthesis is problematic in valve sizes greater than 25 mm and among patients younger than 70 years of age. The present report moves the target population to those with a small annulus and age greater than 75 years. Scrutiny of the present data confirms high rates of structural valve deterioration among patients less than 75 years, but also suggests significant attrition of structural integrity at 5 years among patients between 75 and 84 years at the time of surgery. The ideal heart valve prosthesis may be the Holy Grail of heart valve surgery. We seek a prosthesis that has good hemodynamics, low rates of adverse events, and is durable. Is two out of three not bad? At present, with the availability of alternative heart valve prostheses that come increasing close to meeting all three criteria, it is difficult to imagine a rationale for the use a prosthesis that is known to deteriorate after only 5 years. David S. Bach, MD The University of Michigan L3119 Women s 0273 1500 E Medical Center Dr Ann Arbor, MI 48109 e-mail: dbach@umich.edu Reference 1. Minami K, Zitterman A, Schulte-Eistrup S, Koertke H, Körfer R. Mitroflow synergy prostheses for aortic valve replacement: 19 years experience with 1,516 patients. Ann Thorac Surg 2005;80:1699 705. Dr Bach discloses a financial relationship with Edwards Lifesciences, Medtronic, and St. Jude Medical. 2005 by The Society of Thoracic Surgeons 0003-4975/05/$30.00 Published by Elsevier Inc doi:10.1016/j.athoracsur.2005.05.096