Isolated Mitral Valve Replacement With St Jude Medical Prosthesis
Long-Term Results: A Follow-Up of 19 Years
Background—In this retrospective study, ≈440 patients received mitral valve replacements with the St Jude Medical prothesis. The last patient was operated on 10 years before the beginning of the follow-up. The extended follow-up was 19 years.
Methods and Results—Four hundred forty patients (sex ratio, 1.32 [men to women]; age, 60±11.4 years; age range, 7 to 75 years) were operated on from 1979 to 1987. All patients underwent isolated mitral valve replacement. Tricuspid plasty was the only associated procedure. The follow-up at 19 years was 98% complete. The overall actuarial survival rate was 63±3.3% at 19 years, and the actuarial survival rate (only valve related) was 83±2.7%. The operative mortality rate (0 to 30 days) was 4.09%. We found that 89.4% of the patients alive at 19 years were in NYHA class I/II. Multivariate analysis showed that age and sex were significantly correlated with valve-related mortality and that age, sex, NYHA class, and atrial fibrillation were significantly correlated with overall mortality. The linearized rates (percent patient-years) of thromboembolism, thrombosis, and hemorrhage were 0.69, 0.2, and 1, respectively. At 19 years, freedom from endocarditis and reoperation was 98.6±1% and 90±3%, respectively.
Conclusions—In this study, the very-long-term results confirm the excellent durability of the St Jude Medical prosthesis in the mitral position and show the difficulty of adjusting the anticoagulation protocol, even after long-term treatment.
The St Jude Medical (SJM) prosthesis was the first bileaflet mechanical prosthesis implanted in 1978 in Europe. Within a few years, this prosthesis became the gold standard for mitral valve replacement. Its low-profile design and high biocompatibility explain its excellent hemodynamic performance. We implanted this prosthesis in 870 patients from February 1979 to December 1989 at our institution.1 From this cohort, we extracted a homogeneous subgroup of 440 patients operated on for isolated mitral valve replacement. A retrospective study was conducted with a 19-year follow-up to confirm the excellent durability of this prosthesis. The last patient was operated on 10 years before the beginning of the follow-up.
From 1979 to 1987, 440 patients were operated on for isolated mitral valve replacement with an SJM prosthesis. Tricuspid plasty was the only associated procedure (6.8%). CABG and aortic valve replacement were excluded from this study. Patients were predominantly male (sex ratio, 1.32; Table 1⇓) with a mean age of 60±11.4 years (range, 7 to 75 years). Rheumatic disease was the main (60.45%) cause of heart disease. Stenosis and insufficiency rates were similar (Table 1⇓). Preoperatively, 75% of patients were in NYHA class III/IV (Figure 1⇓), and the atrial fibrillation (AF) rate accounted for 57%.
Myocardial protection was always achieved with mild systemic hypothermia (28°C); pericardial cooling, by Shumway’s technique and anterograde crystalloid cardioplegia (St Thomas and Bretschneider solutions). Urgent procedure was encountered in 4.8% of the patients. Plasty of the tricuspid valve was associated only in patients (6.8%).
The prosthesis diameter most frequently used was 29 mm (Figure 2⇓), and the subvalvular mitral apparatus was never preserved because these techniques were not yet widely used. Coumadin treatment was introduced on the fourth operative day to obtain an international normalized ratio (INR) of 3 to 4; at that time, intravenous heparin administration was stopped.
Continuous variables were expressed as mean±SD and compared by use of Student’s t test or the Mann-Whitney test when appropriate. Qualitative variables were expressed as a percentage and compared by the χ2 test or Fischer’s exact test when appropriate. A value of P<0.05 was considered significant. Multivariate analysis was performed to determine which factors were associated with death or events. The preoperative, intraoperative, and postoperative variables were studied by factorial analysis (multiple correspondence analysis). The variables were extracted from the model when their contribution to the formation extracted from the factorial axis was >80%. These extracted variables were submitted to logistic regression analysis. A variable was identified as a significant independent factor at P<0.05.
The Kaplan-Meier method was used for actuarial analysis. All late mortality and morbidity rates were expressed as linearized rates and by actuarial analysis. Linearized occurrence rates were calculated by dividing the observed number of occurrences of a particular event (death or complication) by the total number of years of patient follow-up. All operative deaths were included in actuarial survival analysis. The log-rank test was used for the comparison of 2 event-free curves.
AF (13.3%) was the main postoperative complication, followed by low cardiac output (5.6%; Table 2⇓). The operative mortality rate (0 to 30 days) was 4.09% (Table 3⇓). Of the patients discharged from hospital and alive at the time of follow-up (10 years after the operation on the last patient), 89.4% were in NYHA class I/II (Figure 1⇑), and 75% were in sinus rhythm. Anticoagulation was equilibrated in 80% of patients, with a mean prothrombin time of 30% and a mean INR of 3.3±2.3. At the clinical interview, 77% of patients believed that they had regained normal activity for their age.
The overall actuarial survival rate (including operative mortality) was 61.3±3.3% at 19 years. When only valve-related mortality was considered, the actuarial survival rate was 83.6±2.7% at 19 years (Figure 3⇓).
The 2 main causes of non–valve-related mortality were secondary heart failure (18.2%) and neoplasms (27%). The main cause of valve-related mortality was sudden death (18.1%), which represented 64% of valve-related deaths (Table 4⇓).
Univariate analysis demonstrated a significant correlation between overall late mortality and age (P<0.003), sex (P<0.001), NYHA class (P<0.002), AF (P<0.001), and left ventricular ejection fraction (P<0.017). Only age (P<0.01) and sex (P<0.002) were significantly correlated with valve-related mortality.
Multivariate analysis also showed age and sex to be significantly correlated with valve-related mortality, whereas age, sex, NYHA class, and AF were significantly correlated with overall mortality on multivariate analysis.
Valve-related complications were reported according to the various international guidelines. No structural dysfunction was observed. The most frequent complications were those related to anticoagulants (Table 5⇓) at 1% per patient-year. The valve thrombosis rate was low at 0.2% per patient-year (Table 5⇓).
At 19 years, the percentages of patients free of endocarditis and valve avulsion were 98.6±1% and 90±3%, respectively (Figure 4⇓). Causes of reoperations were as follows: paravalvular leak (with hemolysis or cardiac insufficiency), 12 patients; prosthesis thrombosis, 2 patients; and prosthesis endocarditis, 1 patient.
We updated the follow-up performed in 1994 for 870 patients1 following recommended guidelines.2 3 4 5 Each live pa-tient was reached by telephone and by the attending physician and cardiologist when necessary. Eight patients were lost to follow-up, giving a complete follow-up for 98% of patients. The mean follow-up was 133 months for a total of 4877 patient-years. At the end of this 19-year study, 59.7% of patients (257 of 440) were alive (excluding those patients lost to follow-up).
This very-long-term retrospective study demonstrates the good results of the SJM isolated mitral valve mechanical prosthesis. The thromboembolism rate was relatively low, with no structural dysfunction. This confirms the very good biocompatibility of the SJM valve.6 7 8 This mechanical prosthesis also probably remains the best valve replacement in the mitral position. Rosengaardt et al9 showed a significant difference in the thromboembolism rate between the CARBOMEDICS valve and the SJM valve in the mitral position.
In our study, it is interesting that 20% patients had persistently poorly controlled anticoagulation despite a follow-up of ≥10 years. This clearly reflects the difficulty in the practical management of this treatment, the constraints that anticoagulants can impose on these patients, and the possible alteration of their quality of life. For these reasons, mitral plasty techniques should always be performed when they are technically feasible.10 The main problem is anticoagulation and the complications induced by anticoagulation; in this study, 80% of valve-related complications were related to anticoagulation.
On the other hand, “light” anticoagulant treatment is now recommended for patients in sinus rhythm. This treatment could decrease the incidence of serious hemorrhagic complications. The linearized rate of hemorrhage was not very high in this series, but events like cerebral bleeding were more serious than thromboembolism. Self-monitoring of the INR by the patient, like blood glucose monitoring in diabetics, could improve control of these patients’ anticoagulant treatment in the future.
The proportion of sudden deaths in the valve-related mortality is also subject to discussion11 12 13 because ventricular arrhythmias are probably responsible for a large share of these sudden deaths and therefore cannot be attributed to the prosthesis itself.11 12 Burke et al11 showed in an autopsy study that ≈90% of these sudden deaths were due to ventricular arrhythmia. In our series, 2 of the 3 valve-related deaths were sudden deaths, so the real valve-related mortality rate could be <15% instead of 28%.
In this consecutive series of 440 patients, the mitral subvalvular apparatus was never preserved. It has now been established that partial or total preservation of the subvalvular apparatus improves immediate postoperative left ventricular performance and may decrease the incidence of secondary heart failure.10 14 15 Mitral subvalvular apparatus preservation techniques primarily concern the posteromedial valve leaflet. However, Yun an al15 reported good results with the preservation of all the subvalvular apparatus.
These very-long-term results confirm the excellent biocompatibility and durability of the SJM valve in the mitral position. We hope for the future a totally biocompatible device without anticoagulation to improve long-term results and quality of life.
- Received July 26, 2000.
- Revision received November 29, 2000.
- Accepted December 7, 2000.
- Copyright © 2001 by American Heart Association
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