Asian Cardiovasc Thorac Ann 2007;15:127-133
© 2007 Asia Publishing EXchange Ltd
Aortic and Mitral Prosthetic Valve Replacement in Age Groups 61–65 & 66–70 Years
Kriengchai Prasongsukarn, MD,
WR Eric Jamieson, MD,
Eva Germann, MSc,
Florence Chan,
Samuel V Lichtenstein, MD
University of British Columbia, Vancouver, Canada
For reprint information contact: WR Eric Jamieson, MD Tel: 1 604 806 8383 Fax: 1 604 806 8384 Email: wrej{at}interchange.ubc.ca, 486 Burrard Bldg, St. Paul’s Hospital, 1081 Burrard Street, Vancouver, Canada V6Z 1Y6.
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ABSTRACT
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Prosthesis choice for aortic and mitral valve replacements in patients aged 61–70 years is difficult. We evaluated prostheses in age groups 61–65 and 66–70 years. Freedom from major thromboembolism and hemorrhage was greater for bioprostheses than mechanical prostheses in both age groups after aortic valve replacement, but only in the younger age group after mitral valve replacement. Freedom from valve-related re-operation was greater after mitral valve replacement with mechanical prostheses in both age groups, but no difference after aortic valve replacement. Valve type was predictive of major thromboembolism and hemorrhage, except in older patients undergoing mitral valve replacement. Bioprostheses are favored for aortic valve replacement in both age groups, but the risk of re-operation with a bioprosthesis in the mitral position in patients aged 61–65 years favors a mechanical prosthesis. Prosthesis choice is less definite in those aged 66–70 years.
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INTRODUCTION
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We have previously reported on the performance of bioprostheses (BP) and mechanical prostheses (MP) in the age group 61–70 years.1 The main limitation of that study was the lack of clear documentation of performance; however, we recommended MP for mitral valve replacement (MVR) in the age group 61–70 years because of the reduced risk of re-operation, and BP for aortic valve replacement (AVR) because of reduced risks of thromboembolism (TE) and antithrombotic-related hemorrhage (ARH), with no increased risk of re-operation. In this study, we compared both types of prosthesis in the subgroups of 61–65 and 66–70 years. Patients in these age groups were considered because MP are recommended for AVR in patients < 65 years, and for MVR in those < 70 years; whereas our extensive experience suggests that BP may be used in the aortic position and MP in the mitral position in these age groups.2–4 We evaluated our cumulative experience with MP and BP at the University of British Columbia, specifically the 15-year performance of these types of prosthesis in this population. We considered patient survival, freedom from major TE and ARH, and freedom from valve-related composites to 15 years for both AVR and MVR in an attempt to provide recommendations for the 61–65 and 66–70 years age groups.
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PATIENTS & METHODS
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This was a retrospective study of a prospectively maintained cardiac valve database. The patients had initial cardiac surgery between 1982 and 1998. The prostheses implanted are currently marketed worldwide: BP included Carpentier-Edwards SAV (Edwards Lifesciences, Irvine, CA, USA), Carpentier-Edwards PERIMOUNT (Edwards Lifesciences), Medtronic Mosaic (Medtronic, Inc., Minneapolis, MN, USA); and MP were St. Jude Medical (Standard, HP, and Regent; St. Jude Medical, Inc., St. Paul, MN, USA), and CarboMedics (Standard and Top-Hat; Sorin-CarboMedics, Inc., Austin, TX, USA). The patients were divided into group 1 (aged 61–65 years) and group 2 (aged 66–70 years). There were 627 patients in group 1, of whom 345 had AVR with either BP (195) or MP (150) and 282 had MVR with either BP (146) or MP (136). There were 960 patients in group 2 of whom 577 had AVR with either BP (424) or MP (153) and 383 had MVR with either BP (207) or MP (176). Patient demographics and characteristics are shown in Table 1
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The American Association for Thoracic Surgery guidelines for reporting morbidity and mortality after cardiac valvular operations were used for definitions of valve-related complications, categorization, and statistical methods in this study.5 Valve-related re-operation and mortality were as defined in these guidelines. Valve-related morbidity was defined as permanent neurological or functional impairment. Valve-related re-operation and mortality included structural valve deterioration (SVD), non-structural dysfunction, prosthetic valve endocarditis, and TE + ARH. Valve-related mortality also included sudden unexplained deaths. Patient survival and freedom from valve-related complications were determined by Kaplan-Meier actuarial analysis and expressed as percentage of patients ± standard error. Early mortality was included in the survival analysis. Differences were assessed by log-rank statistic. Freedom from valve-related complications and composites of complications was evaluated by cumulative evidence or actual methodology using modified Kaplan-Meier analysis. Comparison of continuous and categorical variables was carried out using standard methodology. Testing of two proportions for early mortality was undertaken with the z test for 2-tailed probabilities. Evaluation of performance of prostheses by linearized occurrence rates (%/patient-year) had the linearized occurrence rates tested by log likelihood ratio statistics. The predictors of performance were determined for AVR and MVR by univariate and multivariate Cox proportional regression analysis. The variables considered were: valve type, sex, age, concomitant coronary artery bypass grafting (CABG), valve size, ejection fraction, preoperative New York Heart Association (NYHA) functional class, diabetes mellitus, chronic obstructive pulmonary disease, preoperative renal failure, and follow-up NYHA class. Individual factors potentially predictive of overall mortality and freedom from valve-related complications and composites of complications were initially analyzed using univariate analysis. To determine independent predictors of mortality and valve-related complications, all variables with a p value < 0.10 by univariate analysis were entered as covariates in the multivariate analysis by Cox stepwise logistic regression. A value of p < 0.05 was considered significant.
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RESULTS
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The mortality and valve-related complications after AVR are detailed in Table 2. In group 1, the overall survival at 15 years after AVR with BP was 41.1% ± 4.6%, and after AVR with MP it was 70.2% ± 5.5% ( p = 0.09; Figure 1). In group 2, the overall survival after AVR with BP was 28.5% ± 3.3% at 15 years, and after AVR with MP it was 44.2% ± 9.6% at 12 years ( p = 0.09; Figure 2). The mortality and valve-related complications after MVR are detailed in Table 3. In group 1, the overall survival at 15 years after MVR with BP was 27.4% ± 5.0%, and after MVR with MP it was 64.2% ± 6.0% at 12 years ( p = 0.06; Figure 1). In group 2, the overall survival after MVR with BP was 8.8% ± 2.9% at 15 years, and after MVR with MP it was 48.7% ± 7.4% at 11 years ( p = 0.001; Figure 2).
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Figure 1. Patient survival after AVR and MVR in age group 61–65 years. AVR = aortic valve replacement, BP = bioprostheses, MP = mechanical prostheses, MVR = mitral valve replacement.
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Figure 2. Patient survival after AVR and MVR in age group 66–70 years. AVR = aortic valve replacement, BP = bioprostheses, MP = mechanical prostheses, MVR = mitral valve replacement.
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Freedom from TE + ARH after AVR and MVR in group 1 is shown in Figure 3. The actual freedom from TE + ARH after AVR with BP was 89.2% ± 2.6%, and after AVR with MP it was 81.4% ± 4.4% at 15 years (actuarial freedom, p = 0.02). The actual freedom from TE + ARH after MVR with BP was 86.5% ± 3.2% at 15 years, and after MVR with MP it was 78.9% ± 5.0% at 12 years (actuarial freedom, p = 0.03). The freedom from major TE + ARH after AVR and MVR in group 2 is shown in Figure 4. The actual freedom from TE + ARH after AVR with BP was 82.9% ± 2.2% at 15 years, and after AVR with MP it was 70.5% ± 6.9% at 11 years (actuarial freedom, p = 0.0002). The actual freedom from TE + ARH after MVR with BP was 79.8% ± 3.3% at 15 years, and after MVR with MP it was 74.9% ± 5.5% at 11 years (actuarial freedom, p = 0.49).
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Figure 3. Actual freedom from major thromboembolism and hemorrhage after AVR and MVR in age group 61–65 years. AVR = aortic valve replacement, BP = bioprostheses, MP = mechanical prostheses, MVR = mitral valve replacement.
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Figure 4. Actual freedom from major thromboembolism and hemorrhage after AVR and MVR in age group 66–70 years. AVR = aortic valve replacement, BP = bioprostheses, MP = mechanical prostheses, MVR = mitral valve replacement.
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The actual and actuarial freedom from re-operation after AVR and MVR in group 1 is illustrated in Figure 5. The freedom from re-operation after AVR at 15 years was not differentiated by actuarial analysis ( p = 0.59). The actual freedom from re-operation at 15 years was 86.2% ± 3.2% after AVR with BP and 80.8% ± 15.0% after AVR with MP. The freedom from re-operation after MVR at 15 years was differentiated by actuarial analysis ( p = 0.002). The actual freedom from re-operation at 15 years was 66.4% ± 4.3% after MVR with BP and 94.5% ± 4.1% after MVR with MP at 12 years. The actual and actuarial freedom from re-operation after AVR and MVR in group 2 is illustrated in Figure 6. The freedom from re-operation after AVR at 15 years was not differentiated by actuarial analysis ( p = 0.36). The actual freedom from re-operation was 94.7% ± 1.5% after AVR with BP at 15 years, and 99.3% ± 0.7% after AVR with MP at 11 years. The freedom from re-operation after MVR at 15 years was differentiated by actuarial analysis ( p = 0.01). The actual freedom from re-operation was 81.3% ± 3.2% after MVR with BP at 15 years, and 93.2% ± 2.6% after MVR with MP at 11 years.
The predictors of overall mortality after AVR in group 1 were concomitant CABG (hazard ratio [HR] 1.86, p = 0.0017) and preoperative renal failure (HR 3.92, p = 0.0007). The predictors of overall mortality after MVR in group 1 were ejection fraction < 35% (HR 3.25, p = 0.0066), follow-up NYHA class III/IV (HR 2.09, p = 0.0187), and preoperative renal failure (HR 2.58, p = 0.0115). The predictors of overall mortality after AVR in group 2 were valve type (MP > BP; HR 1.46, p = 0.0287), diabetes mellitus (HR 2.19, p = 0.0497), and chronic obstructive pulmonary disease (HR 2.67, p = 0.0012). The predictors of overall mortality after MVR in group 2 were valve type (MP > BP; HR 1.58, p = 0.0095), concomitant CABG (HR 1.51, p = 0.0104), preoperative NYHA class (HR 1.91, p = 0.0457), and follow-up NYHA class (HR 1.79, p = 0.0412).
On multivariate analysis, the predictors of major TE + ARH and valve-related re-operation after AVR and MVR are detailed in Tables 4 and 5. In group 1 patients undergoing AVR, valve type influenced TE + ARH (MP > BP); in MVR, valve type influenced TE + ARH and valve-related re-operation (BP > MP). In group 2 patients undergoing AVR, valve type influenced TE + ARH (MP > BP); in MVR, valve type had no influence on either valve-related complication.
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Table 4. Predictors of Valve-related Re-operation, Thromboembolism, and Hemorrhage after Aortic Valve Replacement
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Table 5. Predictors of Valve-related Re-operation, Thromboembolism, and Hemorrhage after Mitral Valve Replacement
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DISCUSSION
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The results of cardiac valve surgery depend on numerous factors including type of surgery (reconstruction or replacement), type of prosthesis, and patient-related factors such as cardiac function. Traditionally, the choice of valvular prosthesis is made by considering the balance of complications (TE + ARH) with a MP, and re-operation for SVD with a BP. The guidelines published in 1998 by the American Heart Association and American College of Cardiology recommend MP for MVR in patients < 70 years and for AVR in patients < 65 years.6 The Canadian Cardiovascular Society consensus on surgical management of valvular heart disease published in 2004 provides the same recommendations.7 The AVR recommendations incorporated BP for patients at least 65 years of age and MP below that age. For MVR, BP have a limited role, most commonly over 70 years of age. Mechanical prostheses are indicated for patients 70 years of age or younger, even though there is significant valve-related morbidity. This study challenges those recommendations, especially for AVR, but not necessarily for MVR.
The published data support the main advantages of BP, either porcine or pericardial, which are a lower incidence of ARH and limited need for antithrombotic therapy.8 These studies demonstrated a lower rate of SVD in patients > 65 years than in patients
65 years, especially after AVR. In patients > 65 years undergoing AVR with porcine BP, the rate of SVD is < 10% over 10 years.9–11 The performance of pericardial BP is more varied, some demonstrate a lower rate of SVD than porcine BP in patients > 65 years, but one report showed no difference in the older age groups and a preference for pericardial BP in those < 60 years of age.12–14
The choice of valvular substitutes is also based on two randomized trials on obsolete mechanical and heterograft prostheses.15,16 The Veterans Affairs study reported 15-year outcomes after valve replacement with MP or BP.15 Mitral valve replacement all-cause mortality was similar with both types of prosthesis. There was more SVD with BP for MVR in all age groups, but a much higher rate in those < 65 years. Thromboembolic rates were similar for both types of prosthesis, but ARH was more common with MP. Patients undergoing AVR had better survival with BP than MP.15 Structural valve deterioration was greater with BP for AVR and occurred at a much higher rate in those < 65 years. Re-operation was more common for AVR with BP. Thromboembolic rates were similar with both prosthesis types, but bleeding was more common with MP. The Edinburgh randomized trial reported results to 20 years in 2003.16 Prosthesis type did not influence survival, TE, or endocarditis after AVR and MVR. Major bleeding was more common with MP. The study assessed mortality and re-operation, and reported that survival with the original prosthesis became different at 8–10 years after MVR and 12–14 years after AVR.
The current study compliments and extends the recommendations of the consensus documents and the two randomized trials.6,7,15,16 For AVR, the freedom from TE + ARH favors BP for both age groups. Mechanical prostheses have been identified as a risk factor for TE + ARH and permanent neurologic or functional impairment. Further evidence in favor of BP for AVR for these age groups is that valve-related re-operation was undifferentiated for BP and MP. The study was not as conclusive for prosthesis type in MVR for these age groups. The freedom from TE + ARH favored BP for the 61–65 years group but not the 66–70 years group. Mechanical prostheses were predictive of TE + ARH only in the 61–65 years group. The major factor influencing prosthesis choice for MVR surgery is valve-related re-operation. Mechanical prostheses reduced re-operation rates after MVR in the 61–65 years group but not in the 66–70 years group. The freedom from TE + ARH favored BP for the 61–65 years group, but not for the 66–70 years group. Valve-related residual morbidity, such as permanent neurologic or functional impairment, was not differentiated for BP or MP in either age group.
There are limitations to this retrospective analysis. There was a trend toward longer survival after AVR and MVR with an MP rather than a BP for the 61–65 years age group, but not for the older age group. The difference in survival after MVR with MP > BP for 66–70 year-olds was significant ( p = 0.0016). The prevalence of concomitant CABG was not uniform for AVR in any subgroup; for MVR with BP or MP, it was the same in age group 61–65 years, but very diverse in age group 66–70 years. Concomitant CABG was the likely reason for survival differences because age was uniform in the age groups evaluated. The duration of follow-up was also not uniform.
It was concluded from this study that the risk of major thromboembolism and hemorrhage and permanent morbidity favors bioprostheses for AVR for both 61–65 and 66–70 years age groups. The risk of re-operation after MVR favors mechanical prostheses in the 61–65 years group, but the choice of prosthesis is less well defined in the 66–70 years group.
Presented at the 31st Annual Meeting of the Western Thoracic Surgical Association, Victoria, British Columbia, Canada, June 22–25, 2005.
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REFERENCES
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- ACC/AHA guidelines for the management of patients with valvular heart disease. A report of the American College of Cardiology/American Heart Association. Task Force on Practice Guidelines (Committee on Management of Patients with Valvular Heart Disease). J Am Coll Cardiol 1998;32:1486–588.[Free Full Text]
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- Jamieson WR, Tyers GF, Janusz MT, Miyagishima RT, Munro AI, Ling H, et al. Age as a determinant for selection of porcine bioprostheses for cardiac valve replacement: experience with Carpentier-Edwards standard bioprosthesis. Can J Cardiol 1991;7:181–8.[Medline]
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ABSTRACT
INTRODUCTION
