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Biomedical subjects

R Yozu

Publications and source records attributed to R Yozu.

At least 55 records · Page 3Linked to original sources
PubMed1996

[A successful surgical case of a dissecting aortic aneurysm with right-sided aortic arch and right-sided descending aorta].

The patient was a 70-year-old female whose aortogram and chest computer tomogram revealed DeBakey type IIIb dissecting aortic aneurysm in association with right-sided aortic arch, right-sided descending aorta and aberrant left subclavian artery arising from the Kommerell's diverticulum. Because she had cachexy with hoarseness and difficulty in swallowing caused by an aneurysm she received hypotensive therapy until recovery of her general condition before elective operation. The aneurysm was 7 cm in diameter and was replaced with vascular graft. Reconstruction of the aberrant left subclavian artery and closure of the false lumen via right thoracotomy were also performed under partial bypass installed between the right common femoral vein and artery using modified PCPS. Postoperative computer tomogram and aortogram showed properly replaced vascular graft and closure of false lumen. Dissecting aortic aneurysm complicated with a right-sided arch is quite rare. Including our case, 12 cases have been reported in the world and 9 cases were in Japan. This is one of the most successful surgical case for DeBakey type IIIb dissecting aortic aneurysm in association with right-sided aortic arch, right-sided descending aorta and aberrant left subclavian artery arising from the Kommerell's diverticulum.

Aged↗
PubMed1996

[Surgical repair of a dissecting aortic aneurysm with entry at proximal descending aorta through left thoracotomy--a case report].

A 45-year-old man underwent a distal arch and descending aortic replacement through a left thoracotomy. His chronic type A dissecting aortic aneurysm had the entry at the proximal descending aorta. After 9 years of his first dissection, he suffered from a second dissection. In computerized tomogram (CT), the ascending and descending aorta enlarged to 6.0 cm and 7.0 cm in diameter, respectively and descending aorta showed a three channeled dissection. The open proximal anastomosis technique was used under the deep hypothermic circulatory arrest (HCA) followed by selective cerebral perfusion (SCP). Surgical repair included the obliteration of the proximal false lumen at the level between the left carotid and subclavian artery. A thrombosed retrograde dissection in the ascending aorta was revealed in postoperative evaluation, and decreased in size at follow up CT.

Aortic Dissection↗
PubMed1994

The effect of stimulating voltage on time characteristics of contraction in cardiomyoplasty.

In cardiomyoplasty (CMP), the strength of a skeletal muscle increases as the stimulating voltage increases. On the other hand, timing of stimulation in CMP is a problem not yet solved. This experiment assessed the relationship between stimulating voltage and time characteristics in the contraction of skeletal muscles. In acute experiments using rabbits, the time required to reach maximal muscle contraction did not change significantly with voltage. In conclusion, stimulation voltage does not affect time characteristics. Thus, the best timing of stimulation in CMP can be assessed independently of voltage.

Animals↗
PubMed1994

Do we really need pulse? Chronic nonpulsatile and pulsatile blood flow: from the exercise response viewpoints.

The response of the body and the blood pump was evaluated in animals with a pulsatile artificial heart (total artificial heart [TAH]) and those with a nonpulsatile artificial heart (nonpulsatile biventricular bypass [NPBVB]) subjected to the same exercise load. The animals used in this study were 5 calves implanted with a pusher-plate type TAH (45-206 days) and 5 calves implanted with a nonpulsatile centrifugal pump (34-99 days). The pre-exercise pump flow rate was 92.1 +/- 8.1 ml/kg/min for the TAH group and 94.8 +/- 9.1 ml/kg/min for the NPBVB group, with no significant difference between the two groups. The workload was administered at a rate of 1.5 mph for 15 min. The artificial heart driving conditions were kept constant throughout the test period. Sequential changes in hemodynamic response and metabolism were determined before, during, and for 30 min after exercise. Both TAH and NPBVB calves showed excellent tolerance of the workload (1.5 mph exercise); in NPBVB calves, oxygen demand was compensated for by an increase in the arteriovenous oxygen difference during exercise; and norepinephrine showed a greater response in the NPBVB group. Based on the results presented, the nonpulsatile pump seems to lend itself to a mechanically driven artificial heart of the complete implantation type because of its small size, high efficiency, and the lack of need for a compliance chamber.

Animals↗
PubMed1994

A miniaturized centrifugal pump for assist circulation.

The newly developed Nikkiso HMS-15 is a miniaturized centrifugal pump. It has an impeller diameter of only 50 mm and a priming volume of only 25 ml. A totally new approach was applied to develop this very small pump. The new pump showed comparable hemolysis with pumps twice as big (e.g., the most widely used cone-shaped centrifugal pump [index of hemolysis, 0.005]). This finding refutes the belief that the pump diameter must be sufficiently large in size. Clinical application for cardiac assist was performed for 48 h without any thrombus formation despite low heparin dosage. Also, the pump showed quite favorable blood trauma when applied as a pump for cardiopulmonary bypass during open heart surgery. The compactness, the high controllability, and the system versatility proved to be very effective for clinical application. This pump is considered very reliable for its highly optimized design.

Aged↗
PubMed1994

[Preliminary clinical results of surgery for type A acute aortic dissections using gelatin-resorcin-formaldehyde glue].

We used gelatin-resorcin-form-aldehyde (GRF) glue to fuse the false lumen of type A acute aortic dissection in four patients. All were operated on within 3-24 hours after onset, and gluing of the two cylinders of the dissecting aorta could be done safely in a short time. Initial intimal tears were located in the transverse aorta in three patients and in the proximal descending aorta in one. Simple transection and end-to-end anastomosis of the ascending aorta was done for the first two cases. But in the last two patients, we resected the intimal tear in the transverse aorta and applied GRF glue to the stump of the aortic arch and to that of the aortic root, followed by graft replacement of the ascending aorta. There were no hospital deaths. But we had to reoperate on one patient five months after the first operation due to potentially residual dissection in the aortic root. GRF glue is a very useful adhesive for acute aortic dissection operations, but further refinement of the operative technique using it is necessary.

Acute Disease↗
PubMed1994

[A case of partial atrioventricular canal with discrete subvalvular aortic stenosis worsened 3 years after the replacement of the mitral valve].

The extension of the left ventricular outflow tract is provoked by a partial atrioventricular canal, and is easy to cause stenosis after a radical operation and/or a replacement of the left atrioventricular valve because of its anatomical structure. This report shows a case of a partial atrioventricular canal with a discrete subvalvular aortic stenosis which was worsened three years after the replacement of mitral valve. In this case the left ventricular outflow tract obstruction (LVOTO) had been found before the replacement of mitral valve but it was kept observing without surgical treatment because the degree was judged slight. Subvalvular aortic stenosis was worsened three years after the replacement. It was suspected that the stenosis developed because of the proliferation of heterologous tissue by a turbulent flow of a site of stenosis. For this diagnosis, the transesophageal echocardiography was very effective, and in this case the cause of LVOTO is uncertain, so a careful observation is necessary for it.

Adult↗
PubMed1994

[Removal of infected total pacemaker system under extracorporeal circulation--a case report and review of the Japanese literature].

A 35-year-old male with sick sinus syndrome was complicated with recurrent local infection at the site of the generator pocket associate with a retained pacemaker lead, followed by septicemia presenting with Staphylococcus aureus. Several attempts to remove the lead via the implantation vein by direct traction were performed unsuccessfully because the leads were strongly adhered to the trabecula of the right ventricle. Repeated debridement employing antibiotic therapy was ineffective. As a last resort, we finally operated under extracorporeal circulation (ECC) 24 months after the first implantation and 22 months after initiation of the local infectious episode. As we found it difficult to remove the leads by traction even under direct vision, we used the vinyl chloride tube, which is a part of the ECC circuit, as a sheath for applying countertraction around the lead tip to prevent the myocardial wall from being torn and extracted together with the lead tip. The lead was removed successfully and a new epicardial lead was implanted. The postoperative course uneventful and no recurrence has occurred after 1 year. In reviewing the Japanese literature, 10 case, operated on under ECC to remove the infected retained leads, were described in detail. Among them, eight cases had undergone previous debridement including removal of the generator and the subcutaneous portion of the lead. It is clear that removal of all of the pacemaker system is necessary for eradication of infection. Adhesion of the lead to the wall is firm. Only one case besides ours succeeded in having its lead removed without requiring incision of the tissue around the lead tip.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Redo operations for dissecting aortic aneurysm].

We reoperated twenty-four times upon twenty cases of dissecting aortic aneurysm since 1983. Nine of them (45%) were Marfan patients. Reoperations on the same part of the aorta as the prior procedure was done 15 times upon 13 cases with six hospital deaths (40%). Reoperations on the different part of the aorta from the prior operation was done 9 times on 9 cases with one hospital death (11%). Over all hospital mortality rate was 29%. The hospital mortality rate for Marfan patients (8%) was significantly better than that for non-Marfan patients (50%).

Adult↗
PubMed1993

Assisted circulation using cardiomyoplasty together with aortomyoplasty.

Both dynamic cardiomyoplasty and counterpulsation by the synchronous paced contraction of skeletal muscles in aortomyoplasty can improve ventricular function. The goal of this study was to clarify the effect of cardiomyoplasty combined with aortomyoplasty on cardiac dysfunction in dogs. The percentage of increase in various hemodynamic parameters was calculated during assisted and unassisted cardiac cycles and was compared for three groups: cardiomyoplasty only (Group A), aortomyoplasty only (Group B), and both methods combined (Group C). In Group A, the left ventricular pressure (LVP), systolic aortic pressure (systolic AoP), and dp/dt of LVP (LV dp/dt) increased significantly; the diastolic aortic pressure (diastolic AoP) did not change; and the endocardial viability ration (EVR) decreased during assisted cardiac cycles. In Group B, the diastolic AoP and EVR were improved significantly, but the LVP, LV dp/dt, and systolic AoP were unchanged during assisted cardiac cycles. In contrast to Groups A and B, all parameters were improved in Group C during assisted cardiac cycles. Cardiac assistance using cardiomyoplasty together with aortomyoplasty was more effective than either procedure used alone.

Animals↗
PubMed1992

The valvo-pump, an axial blood pump implanted at the heart valve position: concept and initial results.

The valvo-pump, an axial nonpulsatile blood pump implanted at the heart valve position, has been developed. The valvo-pump consists of an impeller and a motor, which are encased in a housing. An impeller with 5 vanes (22.0 mm in diameter) is used. The impeller is connected to a samarium-cobalt-rare earth magnet direct current (DC) brushless motor measuring 21.3 mm in diameter and 18.5 mm in length. Sealing is achieved by means of a ferrofluidic seal. A pump flow of 10.5 L/min was obtained at a pump differential pressure of 3.3 kPa (25 mm Hg), and a flow of 4.9 L/min was obtained at 7.0 kPa (53 mm Hg). Sealing was kept perfect against a pressure of 29.3 kPa (220 mm Hg) at 9,000 rpm.

Equipment Design↗
PubMed1992

[Extended aortic reconstruction for dissecting aneurysm of the aorta].

While lifesaving palliative surgery may be selected for dissecting aneurysm of the aorta, extended reconstructive surgery has been advocated as a more curative procedure. We performed a variety of extended reconstructive surgeries, for example, replacement of the ascending aorta and the aortic arch, subtotal replacement of the thoracic aorta, replacement of the entire descending thoracic aorta and replacement of the entire descending aorta in 20 cases of dissecting aneurysm of the aorta. However, the operative mortality remained high as 35%, and the operative procedures have not yet to be standardized. We believe that it is extremely important to strive for much greater improvement in the operative results by correct selection of the operative indications, and by improving the operative techniques and patient management during surgery.

Adult↗
PubMed1991

A new technique for bridging to heart transplantation: feasibility of monoventricularization of bilateral ventricles with LVAD.

Because the prognosis of ventricular septal perforation (VSP) and mitral regurgitation (MR) after acute myocardial infarction (MI) is remarkably poor, heart transplantation would be necessary for many of those patients. A new bridging technique was examined in canine models. The bilateral ventricles communicating through VSP were monoventricularized with mitral valve closure and maintained the pulmonary circulation, which had low vascular resistance. The systemic circulation was maintained by a left ventricular assist device (LVAD) placed between the left atrium and the aorta. VSP and MR were made in eight mongrel dogs (pulmonary to systemic flow ratio = 2.24 +/- 0.90). They were then monoventricularized and equipped with LVADs. The hemodynamic state was evaluated (a) in intact hearts, (b) after VSP and MR were made, and (c) after monoventricularization and assisted circulation by LVAD. Cardiac output was (a) 90.60 +/- 23.16, (b) 42.23 +/- 15.76, and (c) 73.43 +/- 15.14 ml/min/kg (a vs. c: not significant; a vs. b and b vs. c: p less than 0.001); mean aortic pressure was (a) 96.75 +/- 24.69, (b) 30.25 +/- 11.08, and (c) 66.50 +/- 18.40 mm Hg (a vs. b: p less than 0.01, a vs. c and b vs. c: p less than 0.05); central venous pressure was (a) 4.76 +/- 1.68, (b) 8.94 +/- 2.17, and (c) 10.68 +/- 2.43 mm Hg (a vs. c: p less than 0.01, a vs. b: p less than 0.05, and b vs. c: not significant). Mean pulmonary arterial pressure and mean left atrial pressure did not show any significant difference among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Early and late operative results of simultaneous aortic valve and ascending aorta replacement].

Thirty-four patients of ascending aortic aneurysm associated with aortic regurgitation were treated with simultaneous aortic valve and ascending aorta replacement utilizing composite graft, until December 1990. Twenty-four patients of the group were diagnosed as Marfan's syndrome and 17 had aortic dissection. For the operative procedure, Bentall's technique were employed in 25 patients and other modifications in nine. Operative death was observed in three cases (8.8%) due to low output syndrome, caused by coronary ostium abnormality, all in Marfan's syndrome. Late death was observed in six including 2 hospital deaths of cerebro-vascular disturbance and sepsis. Other causes of death were rupture of residual aneurysm (in 3) and LOS at reoperation (in 1). Hospital survivors remarkably improved in NYHA class and in cardiac size. Actuarial survival in 3, 5, 7, and 10 years were 78%, 72%, 72%, and 62% respectively. Therefore, surgical result of composite graft technique in our institution proved to be reasonable as others. However, long term result of the procedure should be carefully evaluated, because of the anatomical and histopathological peculiarity of the disease.

Adult↗
PubMed1990

Surgical treatment of arch-type dissecting aortic aneurysms.

We have proposed calling dissecting aortic aneurysm with entry of the dissection in the aortic arch "arch-type". We described the procedures and results of surgery for 12 cases of this disorder. The dissection was localized (type a) in six cases, and extended (type b) in the other six. Seven cases were treated by patch or direct closure of the entry, with one operative death and two later deaths. Five cases were treated by reconstruction of the ascending aorta and the aortic arch with a prosthetic graft, with two operative deaths and one later death. Efforts must be directed towards improving the outcome of the latter operation.

Adult↗
PubMed1990

[Intrathoracic pacemaker implantation in children].

In order to minimize the complications, we introduced the intrathoracic implantation method since 1976. Until 1988, 12 children underwent this method. A pacemaker generator was exchanged in 8 patients, 12 times, because of battery exhaust. Compared with the conventional method (abdominal wall implantation), the complications such as electrode fracture, which was related to the implantation sites, were reduced. Furthermore it was very useful from the cosmetic viewpoint. Although an exchange of generator was very easily done at the first time, it was very difficult at the second time, due to rib fusion accompanying with children's growth.

Adolescent↗