Twenty-Year Outcome of Aortic Valve Replacement With St. Jude Medical Mechanical Valves in Japanese Patients

Abstract

Background: Bioprostheses have become increasingly popular for aortic valve replacement (AVR) in recent years, but mechanical valves are still the standard choice, especially for younger patients. The aim of this study was to assess the very long-term outcomes in Japanese patients who underwent AVR with St. Jude Medical (SJM) mechanical valves.

Methods and Results: From 1991 to 2001, a total of 816 patients underwent AVR with SJM mechanical valves in 5 hospitals. Of these, 801 patients (mean age, 58.3±11.7 years) were analyzed in this study. There were 24 in-hospital deaths (3.0%). Mean follow-up duration was 11.6±6.7 years and the 10-year follow-up rate was 84.1%. Freedom from valve-related death at 5, 10, 15, and 20 years was 96.2%, 92.7%, 88.8%, and 86.6%, respectively. The linearized ratio of major bleeding events and thromboembolic events was 1.1% per patient-year and 1.0% per patient-year, respectively. Freedom from reoperation for the aortic prosthesis was 98.0% and 94.8% at 10 and 20 years, respectively.

Conclusions: The SJM mechanical valve provided excellent long-term freedom from valve-related death and reoperation in patients undergoing AVR. Therefore, this valve should be recommended to younger patients who wish to avoid reoperation. (Circ J 2015; 79: 2380–2388)

In 2014, the American College of Cardiology (ACC) and the American Heart Association (AHA) revised the guidelines regarding the selection of prosthesis in patients with valvular heart disease.¹ The revised guidelines emphasized that the choice of prosthesis should reflect the patient’s values and preferences based on full disclosure and understanding of the indications for anticoagulant therapy and potential need for and risk of reoperation. In terms of age criteria, the new guidelines stipulate that a mechanical valve is a reasonable choice for aortic valve replacement (AVR) in patients <60 years of age who do not have contraindication to anticoagulation, whereas bioprosthesis is a reasonable choice in patients >70 years of age. Furthermore, bioprosthesis or mechanical valve is a reasonable choice in patients between 60 and 70 years of age. There have been several papers reporting the excellent durability of current bioprostheses,^2–5 but it is still a standard practice to recommend mechanical valves in younger patients who want to avoid reoperation despite the need for long-term anticoagulation.⁶ In Japan, the St. Jude Medical (SJM) bi-leaflet mechanical valve (St. Jude Medical, Minneapolis, MN, USA) became available in 1978, and it has been widely used in patients of all ages.^7,8 The SJM mechanical valve provides excellent hemodynamics and promising durability,^9–12 but there are very few reports on very long-term outcome in Japanese patients who underwent AVR with SJM mechanical valves.¹³ The aim of this study was to assess very long-term outcome in the Japanese patients who underwent AVR with SJM mechanical valves after 1991.

Editorial p 2320

Methods

Patients

Between January 1991 and December 2001, 816 adult patients underwent AVR using SJM mechanical valves in 5 Japanese cardiac centers. Of those, 15 patients were excluded from this study because of a lack of informed consent. Therefore, 801 patients formed the present cohort. In addition to isolated AVR, those who underwent aortic root replacement with composite grafts, concomitant procedures such as coronary artery bypass grafting (CABG), mitral or tricuspid valve repair or replacement, and aortic aneurysm repair were also included. Although the level of anticoagulation was left to physician preferences in each institution, international normalized ration (INR) was maintained between 2.0 and 2.5 in patients with isolated AVR in all participating hospitals in this study. Also, the target INR was kept slightly higher in patients undergoing double valve replacement and/or associated with atrial fibrillation (AF). Patient selection and the follow-up process are shown in Figure 1. Patient characteristics and operative data were obtained from medical records at each study center by independent clinical research coordinators according to pre-specified criteria. In addition, all of the patients who survived surgery underwent follow-up surveys. Late outcome was determined from medical records when available, or from written correspondence with referring physicians, direct patient contact via mailed questionnaire or telephone interview where necessary. Clinical data at the latest follow-up were collected by contacting referring physicians. This study was approved by the Institutional Review Board of the Ethics Committee of the Kyoto University Graduate School and Faculty of Medicine, as well as those of all the participating hospitals. All patients or their family members gave informed consent.

Figure 1.

Flow chart of patient selection and follow-up. AVR, aortic valve replacement; SJM, St. Jude Medical.

Definitions of Events

Definitions of valve-related events were based on the Society of Thoracic Surgeons guidelines for reporting mortality and morbidity after cardiac valve interventions, published in 2008.¹⁴ In short, structural valve deterioration (SVD) refers to changes intrinsic to the valve, such as wear, fracture, poppet escape, calcification, leaflet tear, stent creep, and suture line disruption of the components of the prosthetic valve, all of which are very rare or even impossible in mechanical valves. Non-structural dysfunction refers to any abnormality not intrinsic to the valve itself that resulted in stenosis or regurgitation of the operated valve or hemolysis. Non-structural dysfunction includes entrapment by pannus, tissue, or sutures; paravalvular leakage; inappropriate sizing or positioning; residual leakage or obstruction after valve implantation or repair; and clinically important intravascular hemolytic anemia. Thromboembolism refers to any embolic event that occurs in the absence of infection after the immediate perioperative period. A thromboembolism may be manifested by a neurologic event or a non-cerebral embolic event. Neurologic event includes any new central neurologic deficit, whether temporary or permanent, whether focal or global, that occurs after the patient wakes from anesthesia. Central neurologic events that were clearly related to aortic disease, internal carotid artery disease, or vertebral artery disease, such as acute thrombotic occlusion, atheroembolism, or spontaneous arterial dissection, were not counted. When there was no detailed information about the event, however, any neurological event was counted as a thromboembolism in this study. We divided all bleeding events into major bleeding and minor bleeding, according to the following criteria: (1) clinically overt; (2) critical site (intracranial, retroperitoneal, intraocular, spinal, or pericardial); (3) blood transfusion ≥2 units required or a drop in hemoglobin ≥2.0 g/dl; and (4) need for surgical intervention. Major bleeding was defined as satisfying criterion 1 in combination with any of 2, 3 or 4, and minor bleeding as satisfying criterion 1 and none of criteria 2, 3 or 4. Valve-related death was defined as any death caused by structural and non-structural dysfunction, valve thrombosis, embolism, bleeding event, or prosthetic valve endocarditis (PVE); death related to reintervention on the operated valve; or sudden, unexplained death. Deaths caused by heart failure in patients with advanced myocardial disease and satisfactorily functioning cardiac valves were not counted. In-hospital mortality was defined as death occurring within 30 days of surgery or at any time during the index hospitalization.

Statistical Analysis

All clinical events were evaluated at the participating hospitals, and then assessed by the independent clinical events evaluation committee if necessary. Postoperative overall survival, freedom from valve-related death, thromboembolic events, major bleeding events, all bleeding events (combination of major and minor bleeding), reoperation for the aortic prosthesis, and major cardiac reoperation for non-aortic valves and aortic procedures, were estimated using the Kaplan-Meier method. The associations of potential risk factors for survival and events were assessed using log-rank test. All continuous variables are expressed as mean±SD. All P-values are 2-sided and P<0.05 was considered statistically significant. All data analysis was performed by an academic statistician (S.T.) using SAS version 9.2 (SAS Institute, Cary, NC, USA).

Results

Patient preoperative baseline characteristics are listed in Table 1. Mean patient age was 58.3±11.7 years (range, 20–86 years), and 34.6% of the patients were female. AF was relatively common with a prevalence of 21.0%. Chronic kidney disease (defined as estimated glomerular filtration ratio [eGFR] <60 ml/min/1.73 m², calculated using the Modification of Diet in Renal Disease Formula for Japanese Patients [eGFR ml/min/1.73 m²=194×serum creatinine^–1.094×age^–0.287; ×0.739 if female])¹⁵ was also common with a prevalence of 31.1%. A total of 34 patients (4.3%) were dependent on chronic hemodialysis. The majority of the patients were in New York Heart Association (NYHA) functional class I or II, and left ventricular ejection fraction (LVEF) <40% was found in only 7.0% of patients. A total of 30 patients had prior open-heart procedures, of which 12 were prior aortic valve surgeries. In terms of valve pathology, congenital bicuspid valve disease and rheumatic heart valve were identified in 17.1% and in 9.0% of patients, respectively. The causative aortic valve lesions that necessitated AVR were regurgitation (57.3%), mixed lesions (26.1%) and stenosis (15.5%). With regard to operative variables, the size of the prosthetic valve used is listed in Table 2. Isolated AVR was performed in 44.1% of patients, while concomitant procedures were performed in 55.9%. Mitral valve replacement was the most commonly performed concomitant procedure, followed by CABG, and aortic aneurysm repair including aortic root replacement with composite graft. Details of concomitant procedures are given in Table 2. Mean aortic cross-clamp time and cardiopulmonary bypass time were 112±45 min and 161±63 min, respectively.

Table 1. Baseline Characteristics

Characteristics
No. patients	801
Age (years)	58.3±11.7 (20–86)
Age <65 years	533 (66.5)
Female gender	277 (34.6)
Age distribution (years)
20–29	26 (3.2)
30–39	27 (3.4)
40–49	114 (14.2)
50–59	214 (26.7)
60–69	300 (37.5)
70–79	118 (14.7)
≥80	2 (0.2)
BSA (m2)	1.59±0.18
LVEF (%)	63.9±14.0
Comorbidity
Hypertension	341 (42.6)
Dyslipidemia	81 (10.1)
Diabetes mellitus/on insulin	70/10 (8.7/1.2)
Atrial fibrillation	163 (21.0)
COPD	3 (0.4)
Peripheral artery disease	15 (1.9)
Chronic kidney disease (eGFR <60)	236 (31.1)
Hemodialysis	34 (4.3)
Malignancy	15 (1.9)
Coronary artery disease	128 (16.0)
Old myocardial infarction	17 (2.1)
LVEF ≤40%	47 (7.0)
Prior cerebral infarction	70 (8.7)
Prior intracranial hemorrhage	16 (2.0)
Marfan syndrome	15 (1.9)
NYHA functional class
I/II	111/325 (71.2)
III/IV	153/23 (28.8)
Redo sternotomy	30 (3.7)
Aortic valve pathology
Redo/aortic valve redo	30/12 (3.7/1.5)
Bicuspid	137 (17.1)
Rheumatic	72 (9.0)
Active infective endocarditis	37 (4.6)
Healed infective endocarditis	10 (1.2)
Prosthetic valve dysfunction	10 (1.2)
Aortic valve lesion
Aortic stenosis	124 (15.5)
Aortic regurgitation	459 (57.3)
Mixed lesion	209 (26.1)

Data given as mean±SD (range) or n (%). BSA, body surface area; COPD, chronic obstructive pulmonary disease; eGFR, estimated glomerular filtration rate; LVEF, left ventricular ejection fraction; NYHA, New York Heart Association.

Table 2. Operative Variables

Variables
No. patients	801
Valve size (mm)
17	6 (0.8)
19	90 (11.4)
21	210 (26.7)
23	262 (33.3)
25	169 (21.5)
27	43 (5.5)
29	6 (0.8)
31	1 (0.1)
Missing	14
Isolated AVR	353 (44.1)
Concomitant procedure	448 (55.9)
Mitral valve replacement	148 (33.0)
Coronary artery bypass grafting	115 (25.6)
Tricuspid valve repair	76 (16.9)
Mitral valve repair	55 (12.2)
Aortic annular enlargement	13 (2.9)
Aortic aneurysm repair (root/composite)	110 (24.5)
Aortic aneurysm repair (ascending aorta)	37 (8.2)
Aortic aneurysm repair (aortic arch)	28 (6.2)
Mean aortic cross-clamp time (min)	112±45
Mean cardiopulmonary bypass time (min)	161±63

Data given as mean±SD or n (%). AVR, aortic valve replacement.

Early Outcome

There were 24 in-hospital deaths (3.0% of the total cohort). In-hospital mortalities in isolated AVR and complex AVR (concomitant with other procedures) were 1.1% and 4.5%, respectively. Redo patients had a higher mortality rate than first-time AVR patients (6.7% vs. 2.9%). The causes of in-hospital death were predominantly cardiac-related (Table 3).

Table 3. Postoperative and Follow-up Data

Variables
No. patients	801
In-hospital death/mortality	24 (3.0)
Isolated AVR	4 (1.1)
Complex AVR	20 (4.5)
First-time AVR	22 (2.9)
Redo AVR	2 (6.7)
Cause of in-hospital death (n=24)
Cardiac	16 (66.7)
Infection	3 (12.5)
Multi-organ	2 (8.3)
Gastrointestinal	1 (4.2)
Renal	1 (4.2)
Hemorrhage	0 (0)
Respiratory	0 (0)
Others	1 (4.2)
Late death	257 (32.1)
Cause of late death
Malignancy	42 (16.3)
Cerebrovascular	38 (14.8)
Respiratory	34 (13.2)
Cardiac	28 (10.9)
Infection	18 (7.0)
Aneurysm-related	6 (2.3)
Gastro-intestinal	4 (1.6)
Hemorrhage	3 (1.2)
Renal	3 (1.2)
Liver	3 (1.2)
Multiple organ	3 (1.2)
Sudden	21 (8.2)
Unknown	40 (15.6)
Others	14 (5.4)
Valve-related	69 (26.8)
Late complications
Congestive heart failure	77 (9.6)
Prosthetic valve endocarditis	8 (1.0)
Thromboembolism	92 (11.5)
Cerebral infarction	85 (10.6)
Other thromboembolic event	7 (0.9)
All bleeding	163 (20.4 )
Major	91 (11.4)
Intracranial	39
Gastrointestinal	35
Minor	72 (9.0)
Aortic valve reoperation	26 (24 patients: 3.0%)
Indication of reoperation
Non-structural obstruction	12
Paravalvular leak/hemolysis	6/2
Prosthetic valve endocarditis	4
Others (root replacement)	4
SVD or thrombosis	0
Other cardiovascular operation	53 (46 patients: 5.7%)
Procedures
Aneurysm repair	39
Mitral valve repair or replacement	7
Coronary artery bypass grafting	5
Tricuspid valve repair	2
Linearized rates of valve-related complications
Thromboembolic event	1.1%/patient-year
Major bleeding event	1.0%/patient-year
All bleeding (major+minor) event	2.2%/patient-year
Aortic valve reoperation	0.26%/patient-year
All reoperation	0.64%/patient-year

Data given as n (%). AVR, aortic valve replacement; SVD, structural valve deterioration.

Late Outcome

The mean follow-up duration was 11.6±6.7 years (maximum follow-up, 23.3 years). The 10-year follow-up rate was 84.1%. There were 257 late deaths. The causes of late deaths are listed in Table 3. The leading causes of late death were malignancy (16.3%), followed by cerebrovascular (14.8%), respiratory (13.2%), and cardiac (10.9%). Of note, according to the aforementioned criteria, valve-related death was the most common cause of late death (26.8%). In terms of late cardiac complications, 77 patients (9.6%) required hospital re-admission due to congestive heart failure. PVE was very rare, identified in only 8 patients. Thromboembolic events occurred in 92 patients; of those, 85 patients had cerebral infarction. Some patients had ≥2 episodes of cerebral infarction, therefore there were 103 cerebral infarction events in total. Of note, the mortality rate for cerebral infarction was very high at 19.4%. In contrast, major bleeding occurred in 91 patients. The most common major bleeding incidents were intracranial hemorrhage in 39, followed by gastrointestinal bleeding in 35. Similarly, some patients had ≥2 episodes of major bleeding, and there were 129 major bleeding events, with a high mortality rate of 16.3%. In addition, 72 patients had minor bleeding (115 events). The most common bleeding sites were the nose, followed by the urinary tract and gastrointestinal sites.

During the follow-up period, there were 26 reoperations (24 patients) for aortic valve prosthesis. The most common indication of reoperation was non-structural valve dysfunction (prosthetic valve obstruction due to obvious pannus formation, n=6; other non-specific causes, n=6). Other indications included paravalvular leak in 6, and PVE in 4. Two out of 6 paravalvular leaks were accompanied by significant hemolysis. In addition, 4 prosthetic valves had been explanted at the time of aortic root replacement for aortic aneurysm repair with no evidence of prosthetic valve dysfunction. No patients required reoperation due to the development of SVD or valve thrombosis in this study. Among 24 patients who required reoperation for aortic valve prosthesis, mean age at initial operation was 50.0±12.1 years. Mean interval between the initial operation and reoperation was 7.7±5.8 years. Among these 24 patients, there were 2 in-hospital deaths (both related to PVE; mortality, 8.3%). In addition to reoperation related to the aortic prosthesis, 46 patients required other cardiac and aortic aneurysm operations (53 procedures) during the follow-up period. The most common procedure was aortic aneurysm repair (n=39), followed by mitral valve repair or replacement in 7, CABG in 5, and tricuspid valve repair in 2. In particular, thoracic aneurysm repair was relatively common (n=29). Mean age at AVR was 52.0±14.6 years, and mean interval between AVR and other cardiac or aortic aneurysm repair operation was 6.9±4.7 years. In-hospital mortality was 9.4%.

Kaplan-Meier survival curves are shown in Figure 2. Freedom from all-cause death was 88.7%, 77.4%, 64.3%, and 52.5% at 5, 10, 15, and 20 years, respectively. Also, freedom from valve-related death was 96.2%, 92.7%, 88.8%, and 86.6% at 5, 10, 15, and 20 years, respectively. Risk factors for all-cause death on log-rank test included older age (P<0.01), depressed LVEF (defined as <40%, P<0.01), complex AVR (combined with other procedures, P=0.03), redo (P=0.04), coronary artery disease (P<0.001), hypertension (P<0.001), diabetes mellitus (P<0.001), chronic kidney disease (P<0.001), and advanced NYHA functional class (P=0.01).

Figure 2.

Freedom from (Left) all-cause death and (Right) valve-related death. AVR, aortic valve replacement.

Freedom from valve-related events is shown in Figures 3–5. Freedom from thromboembolic events at 10 and 20 years was 90.7% and 78.5%, respectively. The linearized rate of thromboembolic events was 1.1% per patient-year. Also, freedom from major bleeding events at 10 and 20 years was 92.4% and 80.2%, respectively. The linearized rate of major bleeding events was 1.0% per patient-year. In addition, freedom from all bleeding events at 10 and 20 years was 85.8% and 65.9%, respectively. The linearized rate of all bleeding events was 2.2% per patient-year. Although preoperative AF was not identified as a risk factor for major bleeding events (log-rank P=0.18), it was found to be a significant risk factor for thromboembolic events (log-rank P<0.01). In addition, age (≥65 years, log-rank P=0.82), concomitant MVR (log-rank P=0.23), LVEF (<40%, log-rank P=0.31) were not found to be significant risk factors for thromboembolic events.

Figure 3.

Freedom from (Left) thromboembolic event and (Right) major bleeding event. AVR, aortic valve replacement.

Figure 4.

Freedom from (Left) all bleeding event and (Right) aortic valve reoperation. AVR, aortic valve replacement.

Figure 5.

Freedom from (Left) aortic valve reoperation vs. age and (Right) all reoperation. AVR, aortic valve replacement.

Freedom from reoperation for the aortic prosthesis was 98.0% and 94.8% at 10 and 20 years, respectively (Figure 4). There was no significant difference between the younger group (age <65 years) and older group (age ≥65 years, P=0.23). Freedom from all reoperation including aortic prosthesis reoperation, and other cardiac/aortic procedures was 93.2% and 87.3% at 10 and 20 years, respectively, with no significant difference between age groups (P=0.18).

Discussion

More and more patients undergoing AVR in recent years have received a bioprosthesis because of the excellent long-term durability and lack of need for anticoagulation as long as the patient remains in sinus rhythm.¹⁶ It is also true, however, that all bioprosthetic valves will eventually wear out and cause valve dysfunction. Although recent advances in the catheter-based technology have made possible a valve-in-valve strategy in patients who develop bioprosthetic SVD,¹⁷ there are no clear data on the long-term outcome of such new technology. We recently reported that approximately half of the patients who undergo AVR with a pericardial valve at age <65 years required reoperation due to SVD within 15 years of the surgery.^18,19 Therefore, a mechanical valve is still the standard recommendation, especially in younger patients who have no contraindication to anticoagulation and who wish to avoid reoperation. To the best of our knowledge, this is the largest study with the longest follow-up to demonstrate the excellent long-term outcomes of the SJM mechanical prosthesis in the aortic position in Japanese patients.

One of the best features of mechanical valves is their long-term durability. Mechanical heart valves are known to be almost indestructible despite the innumerable leaflet movements of opening and closing. We have not discovered a single case of malfunction due to the intrinsic mechanism of the SJM valve in the relevant literature.^7–12 This virtually guarantees a lifetime of normal functioning of the valve in most patients, and this definitely plays a significant role in preserving myocardial function. Needless to say, reoperation for mechanical aortic valves is very rare. It should be noted that pannus formation is the most common reason for prosthetic valve obstruction. Out of 26 reoperations for replacement valve in the present cohort, we identified 6 definite and another 6 possible cases of obstruction caused by pannus formation. The mechanism of pannus formation is not fully understood. Pannus formation may be associated with a tissue healing process related to transforming growth factor causing excess intimal hyperplasia at annulus.²⁰ Also, it may be related to inadequate anticoagulation.²¹

Despite the excellent durability of the mechanical valves, patients may require another cardiac and aortic surgery late after surgery. Although very few underwent mitral valve procedure or CABG as redo operation in the present cohort, a significant number of patients required aortic aneurysm repair. Among 33 aortic procedures, there were 23 thoracic aortic aneurysm repairs, 3 thoracoabdominal aortic aneurysm repairs, and 7 abdominal aortic aneurysm repairs. The present cohort included 137 patients who had bicuspid aortic valve pathology and 15 patients who had Marfan syndrome, both of which are known risk factors for aneurysm formation. One should keep in mind that aortic aneurysm formation is not uncommon in such patients.²²

The incidence of thromboembolic events after AVR with mechanical valves ranges from 0.5% to 3.5% per patient-year according to the previous reports.²³ The present result (1.1% per patient-year) is consistent with or even lower than these other studies. For the last 2 decades, it has been standard practice in Japan to maintain INR slightly lower than that in the Western countries.^7,8 In the most recent Japanese guidelines, the target INR in patients receiving bi-leaflet or modern single-tilting-disc mechanical valves in the aortic position is 2.0–2.5,²⁴ while the ACC/AHA guidelines define the target INR at 2.5 (range, 2.0–3.0).¹ Given an acceptable range of INR control of 0.5 on both sides, it is true that Japanese patients have relatively lower INR, but there are no differences in the thromboembolic event rate between Japan and the Western countries. Another important finding of this study regarding late thromboembolic events is that the mortality rate of cerebral infarction was very high at approximately 20%, which indicates that embolic stroke often causes extended damage, which is likely accompanied by intracranial hemorrhage.

In terms of bleeding events, the incidence of the major bleeding was 1.0% per patient-year in this study, which is slightly higher than those of 2 previous Japanese SJM studies reported 20 years ago (0.1–0.4% per patient-year).^7,8 This seems, however, to be an acceptable rate compared with several recent reports on other bi-leaflet mechanical prostheses.^25–27 Similar to the findings for thromboembolic events, the mortality rate of major bleeding events was also very high at 16.3% in the present cohort. Two of the most common bleeding sites were intracranial and gastrointestinal, both of which can lead critical conditions. Prompt diagnosis and optimal treatment are essential in both serious thromboembolic events and bleeding events.

Another important aspect of the risk of intracranial hemorrhage is racial/ethnic differences.²⁸ Compared with white patients, the adjusted hazard ratio for intracranial hemorrhage in Asian patients receiving warfarin therapy was 4.06 (95% CI: 2.48–6.66, P<0.0001) although there were no differences in terms of the intensity of anticoagulation between white and Asian patients. These findings would also strengthen the validity of the policy to maintain INR slightly lower in Japanese patients than Western patients to minimize the risk of intracranial hemorrhage. As an adjunctive tool to better maintain target INR, home INR monitoring systems may play an important role in addition to regular clinical visits,²⁹ although this system has not yet been approved for reimbursement by the Japanese Government.

Although there have been numerous retrospective cohort studies comparing the outcomes of tissue vs. mechanical valves,³⁰ there have been only a few prospective randomized control clinical trials comparing tissue and mechanical prostheses. In the Veterans Administration Cooperative Study on Valvular Heart Disease, Hammermeister et al concluded that patients who underwent AVR with mechanical valves had better survival at 15 years than those who received tissue valves.³¹ In contrast, in the Edinburgh trial, Oxenham et al found that there were no differences in the 20-year survival rate between mechanical and tissue valves.³² Of note, the mechanical and tissue prostheses used in those 2 prospective randomized trials were first-generation prostheses, which are no longer used in current practice. Therefore, the findings of those 2 studies may have limited relevance in the present day. Another prospective randomized trial, which was conducted more recently in Italy, found that there were no significant differences in survival, freedom from thromboembolic events, and bleeding events between patients with mechanical valves (SJM or CarboMedics bi-leaflet) and tissue valves (CEP or CE Porcine).³³ Although there does not seem to be much difference in terms of long-term survival between mechanical valves and bioprosthetic valves, mechanical valves have been the standard recommendation for younger patients. As such, the present findings will surely be valuable in helping patients choose the most suitable prosthesis.

Study Limitations

There were several limitations in this study. First, this was a retrospective, non-randomized study. Also, many of the patients died several years prior to the study, and events occurred years before the study was performed, making it difficult to obtain accurate information, especially for valve-related events. Likewise, the 10-year follow-up completeness was 84.1%. These factors may have influenced the results significantly.

Conclusions

The SJM mechanical valve provided excellent long-term freedom from valve-related death and reoperation in AVR patients. Therefore, this valve should be recommended to younger patients who wish to avoid reoperation.

Acknowledgments

This work was supported by an educational grant from the Research Institute for Production Development (Kyoto, Japan). We are indebted to the participating hospitals, investigators, and clinical research coordinators for their great contributions to data collection. The participating hospitals were as follows: Cardiovascular Center Hokkaido Ohno Hospital (Sapporo), Gunma Cardiovascular Center (Maebashi), Nagoya University Hospital (Nagoya), Kyoto University Hospital (Kyoto), and Kumamoto Central Hospital (Kumamoto). Clinical research coordinators: Ms Yui Kinoshita, Ms Asuka Takahashi, and Ms Miya Hanazawa.

Conflicts of Interest

None declared.

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