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Hiroshi Okuyama

Publications and source records attributed to Hiroshi Okuyama.

12 recordsLinked to original sources
PubMed2006

Midterm results of mitral valve repair with the Carpentier-Edwards rigid ring.

OBJECTIVE: Prosthetic annuloplasty rings play an important role in mitral valve repair. This clinical study was undertaken to evaluate the midterm results obtained with the Carpentier-Edwards rigid ring. METHODS: Between October 1991 and March 2005, 112 patients (mean age 53.0 years) underwent mitral valve repair with a Carpentier-Edwards rigid ring at our institution. Degenerative disease was the most frequent cause and a small number had other conditions such as endocarditis and rheumatic disease. Ten patients were in Carpentier's functional class Type I, 101 patients in Type II and 1 patient in Type III, based on valve pathology. Ischemic mitral regurgitation was excluded. The mean follow-up time was 5.3+/-3.6 years (range: 8 days to 12.3 years). All patients were completely followed by echocardiography. RESULTS: The rigid ring ranged from 26 to 36 mm in diameter and the most common size was 30 mm. Although the mitral orifice area was decreased after mitral valve repair in all patients, none of them required reoperation because of mitral stenosis or left ventricular outflow tract obstruction (systolic anterior motion). Reduction of both systolic and diastolic left ventricular volumes was observed postoperatively. Ejection fractions were preserved in all cases. The actuarial survival rate was 92.0+/-3.0% at 10 years and the reoperation-free rate at 10 years was 96.0+/-2.0%. CONCLUSION: The rigid ring has produced promising midterm results in terms of reoperation-free and survival rates.

Adolescent↗
PubMed2006

Prevalence of pannus formation after aortic valve replacement: clinical aspects and surgical management.

Pannus formation after aortic valve replacement is not common, but obstruction due to chronic pannus is one of the most serious complications of valve replacement. The causes of pannus formation are still unknown and effective preventive methods have not been fully elucidated. We reviewed our clinical experience of all patients who underwent reoperation for prosthetic aortic valve obstruction due to pannus formation between 1973 and 2004. We compared the initial 18-year period of surgery, when the Björk-Shiley tilting-disk valve was used, and the subsequent 13-year period of surgery, when the St. Jude Medical valve was used. Seven of a total of 390 patients (1.8%) required reoperation for prosthetic aortic valve obstruction due to pannus formation. All seven patients were women; four patients underwent resection of the pannus and three patients needed replacement of the valve. The frequency of pannus formation in the early group was 2.4% (6/253), whereas it was 0.73% (1/137) in the late group (P < 0.05). Pannus was localized at the minor orifice of the Björk-Shiley valve in the early group and turbulent transvalvular blood flow was considered to be one of the important factors triggering its growth. We also consider that small bileaflet valves have the possibility of promoting pannus formation and that the implantation of a larger prosthesis can contribute to reducing the occurrence of pannus.

Adult↗
PubMed2006

Prevalence and avoidance of patient-prosthesis mismatch in aortic valve replacement in small adults.

BACKGROUND: It is still controversial as to whether a small prosthesis should be inserted or a small aortic annulus should be enlarged to minimize patient-prosthesis mismatch (PPM). This retrospective study reviewed our strategy for avoiding PPM. METHODS: Isolated or combined aortic valve replacement was performed in 181 patients, including 24 patients (13.3%) aged less than 65 years with a small aortic annulus (< or = 21 mm) who underwent enlargement of the annulus by the Manouguian (n = 18) or Nicks (n = 6) procedure. In patients aged 65 years or more, a Carpentier-Edwards Perimount pericardial (CEP) valve was implanted with few exceptions. We assessed our strategy for avoiding PPM by comparison with published normal reference values for the indexed effective orifice area. RESULTS: A CEP valve was implanted in 53 patients, and St. Jude Medical (SJM) mechanical valves were used in 128 patients. A standard 21-mm SJM valve was only used in 4 patients and no 19-mm valves were employed. However, 19-mm CEP valves were used in 12 older patients with a small body surface area (1.43 +/- 0.14 m2). No patient receiving an SJM valve had an indexed effective orifice area of 0.85 cm2/m2 or less, and PPM developed in only 2 (3.8%) of 53 patients receiving CEP valves. Consequently, the prevalence of PPM was 1.1%. The 10-year survival rates of patients receiving CEP or SJM valves with or without annular enlargement were similar. CONCLUSIONS: The prevalence of PPM was low in patients more than 65 years old with a relatively small body size who received bioprosthetic valves. In patients less than 65 years old with a small annulus, the method of first choice for avoiding PPM is aortic annular enlargement.

Adolescent↗
PubMed2006

Long-term results of triple-valve procedure.

Triple-valve procedures are associated with high early and late mortality. We reviewed our experience in 25 patients who underwent combined mitral and aortic valve replacement with tricuspid valve repair or replacement between 1979 and 2004. The mean follow-up was 7.8 years (range, 10 days to 24.5 years). The mean age at operation was 52 years (range, 31 to 72 years). Four patients underwent triple-valve replacement and 21 had double-valve replacement and tricuspid annuloplasty. Perioperative mortality was 20% and late mortality was 24%. Cumulative survival, calculated taking perioperative mortality into account, was 71% +/- 10% at 10 years and 36% +/- 15% at 15 years after surgery. Only 1 of 20 perioperative survivors required re-operation for prosthetic valve dysfunction. Double-valve replacement with tricuspid annuloplasty offers satisfactory long-term survival with freedom from thromboembolism and re-operation.

Adult↗
PubMed2005

Carpentier-Edwards pericardial aortic valve in middle-aged patients: comparison with the St. Jude Medical valve.

OBJECTIVE: The objective of the present study was to compare long-term results of single aortic valve replacement (AVR) with mechanical (St. Jude Medical valves: standard) and biologic (the Carpentier-Edwards pericardial) prostheses. METHOD: Between 1995 and 2002, 95 patients who underwent single AVR with mechanical (n= 46) or biologic (n= 49) prostheses were enrolled in this study. The mean age at the operation was 54.0 +/- 9.6 years (range: 20 to 69 years) with the mechanical and 68.8 +/- 7.1 years (range: 44 to 85 years) with the biologic prosthesis. RESULTS: The 9-year actuarial survival rate, which was calculated by taking perioperative mortality into account, was 90.3 +/- 4.6% for patients with mechanical valves and 87.6 +/- 4.8% for patients with bioprostheses, with no difference between the two groups (p=0.342). The 9-year freedom rate from thromboembolism, reoperation, endocarditis was 94.8 +/- 3.6%, 100% and 97.8 +/- 2.2% for patients with mechanical valves and 98.0 +/- 2.0%, 97.5 +/- 3.4% and 95.0 +/- 3.4% for those with bioprostheses, respectively. After 9 years, freedom from cardiac death averaged 97.8% in the group with mechanical valves compared with 95.3% in those with bioprostheses (p=0.541). CONCLUSION: We conclude that the mid-term durability of the Carpentier-Edwards pericardial valve in the aortic position for the elderly is excellent. Nevertheless, the risk of tissue valve reoperation progressively increases with time, and a longer follow-up may be necessary to provide its value compared with the mechanical valves in a country like Japan with a high life expectancy.

Adult↗
PubMed2005

Long-term assessment of mitral valve reconstruction with resection of the leaflets: triangular and quadrangular resection.

BACKGROUND: The procedure of quadrangular resection and suture for prolapsed posterior leaflet of the mitral valve is a reliable and reproducible method that achieves excellent long-term results. However, triangular resection and suture of a prolapsed anterior leaflet is not widely supported and different techniques have been advocated. The aim of this study was to review our experience of mitral valve repair in which resection of the anterior and/or posterior leaflets was performed. METHODS: Between October 1991 and September 2003, 105 patients with mitral regurgitation underwent mitral valve reconstruction with leaflet resection, including 55 patients with quadrangular resection of the posterior leaflet (P), 32 patients with triangular resection of the anterior leaflet (A), and 18 patients with resection of both leaflets (A+P). RESULTS: The mean follow-up period was 63.6 (1 to 139) months. Reoperation was required in 2 patients, each after resection of the anterior or posterior leaflet. The freedom from reoperation rates at 10 years in 93% +/- 5% of patients after triangular resection of the anterior leaflet, 96% +/- 3% after quadrangular resection of the posterior leaflet, and 100% after resection of both leaflets. There were no significant differences of survival or risk of reoperation among these three groups. The postoperative mitral valve area was significantly smaller than the preoperative area in all three groups, but remained large enough (A: 2.84 +/- 1.07; P: 2.6 +/- 0.87; A+P: 3.09 +/- 1.20 cm2) for adequate valve function. CONCLUSIONS: Triangular resection of a prolapsed anterior mitral leaflet is a reliable, reproducible, and durable procedure, like quadrangular resection of a prolapsed posterior leaflet.

Actuarial Analysis↗
PubMed2005

Midterm results of Manouguian double valve replacement: comparison with standard double valve replacement.

OBJECTIVE: Surgical strategies for patients who have a small aortic annulus associated with a small mitral annulus remain controversial. The objective of this study was to assess the validity of the Manouguian procedure for double valve replacement with patch enlargement of the annuli. METHODS: We reviewed 57 consecutive patients who underwent double valve replacement for combined aortic and mitral disease between September 1991 and October 2000. Thirty patients underwent the Manouguian procedure with patch enlargement of the aortic and mitral annuli, and the other 27 patients had standard double valve replacement. The Manouguian procedure was selected for a small aortic annulus of less than 21 mm in diameter. The patients were followed for a median of 7.5 years. Results of echocardiography and the dobutamine stress test were compared postoperatively. RESULTS: Double valve replacement with the Manouguian procedure did not increase the early or midterm mortality because the survival (including operative death) at 8 years was 83% in the Manouguian group and 84% in the double valve replacement group (P = .82). The event-free rate at 8 years was 79% in the Manouguian group and 84% in the double valve replacement group (P = .6). The prostheses implanted at the aortic and mitral positions were smaller in the Manouguian group, even after annular enlargement. However, the transprosthetic gradient across the aortic valve evaluated by means of dobutamine stress echocardiography did not differ between the 2 groups, possibly because of a smaller body surface area in the Manouguian group. CONCLUSIONS: The Manouguian patch enlargement procedure is useful during double valve replacement when associated with the problem of small-valve annuli.

Adult↗
PubMed2004

Sarcomere-length dependence of lattice volume and radial mass transfer of myosin cross-bridges in rat papillary muscle.

We examined the sarcomere length-dependence of the spacing of the hexagonal lattice of the myofilaments and the mass transfer of myosin cross-bridges during contraction of right ventricular papillary muscle of the rat. The lattice spacing and mass transfer were measured by using X-ray diffraction, and the sarcomere length was monitored by laser diffraction at the same time. Although the lattice spacing and the sarcomere length were inversely related, their relationship was not exactly isovolumic. The cell volume decreased by about 15% when the sarcomere length was shortened from 2.3 micro m to 1.8 micro m. Twitch tension increased with sarcomere length (the Frank-Starling law). At the peak tension, the ratio of the intensity of the (1,0) equatorial reflection to that of the (1,1) reflection was smaller when the tension was greater, showing that the larger tension at a longer sarcomere length accompanies a larger amount of mass transfer of cross-bridges from the thick to the thin filament. The result suggests that the Frank-Starling law is due to an increase in the number of myosin heads attached to actin, not in the average force produced by each head.

Animals↗
PubMed2004

X-ray diffraction from a left ventricular wall of rat heart.

We studied x-ray diffraction from the left ventricular wall of an excised, perfused whole heart of a rat using x rays from the third-generation synchrotron radiation facility, SPring-8. With the beam at right angles to the long axis of the left ventricle, well-oriented, strong equatorial reflections were observed from the epicardium surface. The reflections became vertically split arcs when the beam passed through myocardium deeper in the wall, and rings were observed when the beam passed into the inner myocardium of the wall. These diffraction patterns were explained by employing a layered-spiral model of the arrangement of muscle fibers in the heart. In a quiescent heart with an expanded left ventricle, the muscle fibers at the epicardium surface were found to have a (1,0) lattice spacing smaller than in the rest of the wall. The intensity ratio of the (1,0) and (1,1) equatorial reflections decreased on contraction with a similar time course in all parts of the wall. The results show that it is possible to assign the origin of reflections in a diffraction diagram from a whole heart. This study offers a basis for interpretation of x-ray diffraction from a beating heart under physiologically and pathologically different conditions.

Animals↗
PubMed2002

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Journal Article↗