Biomedical subjects

K Tabayashi

Publications and source records attributed to K Tabayashi.

At least 91 records · Page 5Linked to original sources

PubMed1998

Tricuspid valve closure for neonatal Ebstein's anomaly.

A respirator-dependent 11-day-old boy with Ebstein's anomaly is presented. His cardiac anomaly with progressive cardiomegaly was first noticed at 24 weeks' gestation on fetal echocardiography. After birth, he required mechanical ventilation because of massive tricuspid regurgitation and restricted pulmonary blood flow. The operation of tricuspid valve patch closure, resection of right atrial wall, and central shunt successfully weaned him from the respirator on postoperative day 13. Cavopulmonary anastomosis was performed without problem when the patient was 8 months of age.

Ebstein Anomaly↗

PubMed1998

Brain damage after aortic arch repair using selective cerebral perfusion.

BACKGROUND: Selective cerebral perfusion is one of the most popular methods for cerebral protection during aortic arch repair. However, causes of postoperative brain damage are not fully understood. We analyzed brain damage after aortic arch repair using selective cerebral perfusion for true aortic arch aneurysm in regard to preoperative cerebral infarction and intracranial and extracranial occlusive arterial disease. METHODS: Over a 9-year period, 60 patients with true aortic arch aneurysm underwent aortic arch repair using selective cerebral perfusion. Postoperative brain damage was evaluated in regard to preoperative cerebral infarction detected by computed tomography, magnetic resonance imaging, or both in 50 patients and intracranial and extracranial occlusive arterial disease detected by digital subtraction angiography, magnetic resonance angiography, or both in 35 patients. RESULTS: Seven (12%) of the 60 patients died within 30 days of operation. Postoperative brain damage occurred in 6 (10.5%) (3, coma, and 3, hemiplegia) of 57 patients; 3 patients who died without awakening were excluded. Preoperatively, old cerebral infarction was detected in 9 patients (18%), and silent cerebral infarction (lacunar infarction and leukoaraiosis) was diagnosed in 26 patients (52%). Postoperative brain damage occurred in 3 (33%) of the 9 patients with preoperative cerebral infarction and in 3 (23%) of 13 patients with negative preoperative brain findings; this excludes 2 patients who died without awakening. No patient with silent cerebral infarction had postoperative brain damage. Occlusive arterial disease was detected in 7 patients (20%). The incidence of brain damage in these patients was 71% (5/7), which was significantly greater than that of 4% (1/28) in patients without occlusive arterial disease (p < 0.001). CONCLUSIONS: Silent cerebral infarction may not be a risk factor for postoperative brain damage. Preoperative evaluation of intracranial and extracranial occlusive arterial disease provides important information as to whether a patient might sustain brain damage after aortic arch repair using selective cerebral perfusion.

Aged↗

PubMed1998

Surgical indication for congenital heart disease with extremely thickened media of small pulmonary arteries.

BACKGROUND: Nineteen patients (mean age, 7.6 months) with a percent wall thickness of more than 33% in the small pulmonary arteries were found to have extremely thickened media. Based on our findings, a criterion of operative indication is proposed. METHODS: The percentage of extremely thickened media of small pulmonary arteries for all pulmonary arteries was determined on microscopic lung sections and was introduced as an index for operative indication. RESULTS: Operative repair was performed in 16 patients: 9 died intraoperatively and 7 survived more than 12 months. In 4 of 5 patients that had pulmonary artery banding, medial hypertrophy remained despite pulmonary artery banding. Operative repair also had no positive effect. In operative and late deaths and in survivors without a decrease of pulmonary arterial pressure, the percentage of extremely thickened media of small pulmonary arteries was shown to be more than 10%, whereas in 5 survivors and 1 operative death with a significant postoperative decrease of pulmonary arterial pressure, the value was less than 7%. CONCLUSIONS: If a patient has less than 7% of small pulmonary arteries with extremely thickened media, operative repair is likely to be effective. When the value is higher than 10%, not only operative repair but also pulmonary artery banding cannot be recommended because of ineffectiveness and hazard.

Blood Pressure↗

PubMed1998

Inoperable pulmonary vascular disease in infants with congenital heart disease.

BACKGROUND: Among 120 infants less than 12 months of age who had lung biopsy and autopsy, 20 were inoperable because of severe irreversible pulmonary vascular disease. METHODS: The infants were classified into three groups. Group 1 comprised 6 patients who showed complete obstruction of the small pulmonary arterial lumen and atrophy of the peripheral arterial media and who were considered to have absolute operative contraindications. Group 2 comprised 6 patients who had no pathologic findings of absolute operative contraindication and had an index of pulmonary vascular disease of more than 2.2. They were isolated as having advanced plexogenic pulmonary arteriopathy. Group 3 comprised 8 patients who had extremely thickened media of small pulmonary arteries, with abnormally thickened media extending into the small peripheral arteries characterized by extremely narrow lumina and medial thickness exceeding luminal diameter. RESULTS: Six of the 9 patients in whom operative repair was abandoned on the basis of preoperative or intraoperative lung biopsy are still alive. Of the 11 patients who underwent operation without biopsy, none survived. CONCLUSIONS: Preoperative or intraoperative lung biopsy and assessment of arteriopathy based on the above criteria are recommended in all patients in whom fatal pulmonary vascular disease is suspected.

Atrophy↗

PubMed1998

Delayed and selective motor neuron death after transient spinal cord ischemia: a role of apoptosis?

OBJECTIVE: The mechanism of spinal cord injury has been thought to be related to tissue ischemia, and spinal motor neuron cells are suggested to be vulnerable to ischemia. We hypothesized that delayed and selective motor neuron death is apoptosis. METHODS: Thirty-seven Japanese domesticated white rabbits weighing 2 to 3 kg were used in this study and were divided into two subgroups: a 15-minute ischemia group and a sham control group. Animals were allowed to recover at ambient temperature and were killed at 8 hours, and 1, 2, 4, and 7 days after reperfusion (n = 3 at each time point). By means of this model, cell damage was histologically analyzed. Detection of ladders of oligonucleosomal DNA fragment was investigated with gel electrophoresis up to 7 days of the reperfusion. Immunocytochemistry, in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling staining was also performed. RESULTS: After 15 minutes of ischemia, most of the motor neurons showed selective cell death at 7 days of reperfusion. Typical ladders of oligonucleosomal DNA fragments were detected at 2 days of reperfusion. Immunocytochemistry showed in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end staining was detected at 2 days of reperfusion selectively in the nuclei of motor neurons. CONCLUSION: These results suggest that delayed and selective death of the motor neuron cells after transient ischemia may not be necrotic but rather predominantly apoptotic.

Animals↗

PubMed1998

Enhancement of heat shock protein expression after transient ischemia in the preconditioned spinal cord of rabbits.

PURPOSE: This investigation was designed to evaluate the mechanism used to acquire a tolerance to spinal ischemia. We investigated inductions of the heat shock protein (HSP) 70 gene and protein in rabbit spinal cord with or without preconditioning. METHODS: Neurologic function, morphologic changes, and inductions of HSP70 messenger RNA (mRNA) and protein were compared in the cases of a 15-minute ischemia 2 days after sham treatment and a 15-minute ischemia 2 days after 10-minute preconditioning. RESULT: HSP70 mRNA was induced at 8 hours of reperfusion after a 15-minute ischemia 2 days after sham treatment. HSP70 protein was induced slightly in selective motor neuron cells at 8 hours of reperfusion, and about 70% of motor neuron cells showed selective cell death after 7 days of reperfusion (p < 0.01). On the other hand, large populations of the motor neuron cells survived at 7 days after the 15-minute ischemia that was applied at 2 days after preconditioning (p < 0.01). HSP70 mRNA was induced persistently as compared with the case of a 15-minute ischemia 2 days after sham treatment. The motor neuron cells strongly produced immunoreactive HSP70 from 8 hours to 2 days. CONCLUSION: Preconditioning with 10-minute ischemia enhanced and prolonged the HSP70 gene expression at both mRNA and protein levels and saved the motor neuron cells from subsequent lethal ischemia. These changes of HSP70 gene expression may play an important role in the acquisition of ischemic tolerance of motor neuron cells in rabbit spinal cord.

Animals↗

PubMed1998

Virtual percutaneous transluminal coronary angioplasty system for an educational support system.

With the increase of ischemic diseases of the circulatory system in Japan, the necessity for cardiovascular intervention continues to increase. However, because intervention operations have been developed only recently, the education system for the corresponding specialists in our country has not been established yet. In this study, an intervention educational support system using a virtual reality (VR) technique was developed. Of course, intervention includes percutaneous transluminal coronary angioplasty (PTCA). PTCA is an operation enlarging the stenosis of the coronary artery with a balloon through a guide catheter. The technique that lets the guide wire for the PTCA balloon cross the stenosis is one of the most difficult. A simulation system for the manipulation of a torque device for the PTCA guide wire was developed with this technology for VR. In virtual space, reconstitution of the 3-dimensional coronary artery with atherosclerosis was performed, and the virtual PTCA system was produced experimentally. An interesting system was produced experimentally as a system for the training of doctors studying to become interventional specialists. After the system was combined with an Expert system for treating ischemic heart diseases, its usefulness was steadily increased. With the development of more sophisticated VR methodology in the future, a PTCA training system without using a patient will be embodied.

Angioplasty, Balloon, Coronary↗

PubMed1998

Left heart bypass using the oscillated blood flow with totally implantable vibrating flow pump.

Aiming at a totally implantable ventricular assist device (VAD), a vibrating flow pump (VFP) was developed in Tohoku University. A transcutaneous energy transmission system (TETS) using an amorphous fiber was developed for the totally implantable VAD system. The VFP works with a higher frequency than the natural heart of a biological system, a frequency of 10-50 Hz. In this research, animal experiments on left heart bypass were performed with healthy goats. Blood from the apex of the left ventricle was received and was sent to the aorta so that an adequate supporting effect of the left heart was provided. In particular, the depression effect of the left ventricle was obvious. As a result, sufficient artificial heart flow was provided. For a totally implantable type VAD, left heart bypass of almost 100% may become necessary in some situations. Therefore, apex approaches of left heart bypass may be desirable. From an anatomical consideration, an apex of the heart is suitable for the VFP of this totally implantable type. In the left heart bypass for which the apex of the heart was used, an almost 100% bypass was possible. This is a requirement that is important when waiting for recovery of sufficient cardiac function. It is also important that left heart circulation is maintained fully by an artificial heart of the complete implantation type. The VFP was considered to be useful as a totally implantable type artificial heart from the results.

Animals↗

PubMed1998

Control of the pulmonary arterial resistance by the use of the oscillated assist flow.

In the clinical application of supporting circulation, the treatment of a patient with pulmonary hypertension is very important. We developed the electromagnetically driven vibrating flow pump (VFP) as a totally implantable type ventricular assist system. The artificial heart driven by electromagnetic forces creates high speed oscillation flow around 10-50 Hz. Assistance by high-speed oscillation flow has an interesting influence on the cardiovascular system. In this study, we carried out research on the influence such oscillation flow had on the pulmonary arterial vessels, and the supporting flow wave-form that controlled pulmonary vascular resistance was considered. Six healthy adult goats of both sexes were used in the experiments. We carried out inhalation anesthesia and performed intubation. The thorax was opened through left fourth rib resection. Right heart bypass was performed from the right atrium to the pulmonary artery. The flow of right heart assistance was maintained within 20-25% of total flow. Our purpose was to add flow of a specific high frequency to the right heart circulation. The hemodynamic parameters were recorded on a magnetic tape data recorder and input into a computer through an A-D converter. A result identified was that the pulmonary vascular resistance changed according to the alteration of the driving frequency of the VFP even during the same flow assistance. The resistance of the pulmonary arterial vessels became smaller when the driving of the VFP of 30 Hz was added to the right heart circulation. This was significant even when compared with continuous flow right heart assist. The characteristics of impedance appeared to have interesting alterations as well. Control of pulmonary vascular resistance by right heart assistance becomes possible if these results are applied. Accordingly, it may become one of the choices for treatment of a patient with pulmonary hypertension.

Animals↗

PubMed1998

Inductions of 3-L-nitrotyrosine in motor neurons after transient spinal cord ischemia in rabbits.

The induction and distribution of 3-L-nitrotyrosine (NO2-Tyr) were examined with HPLC and immunohistochemistry in rabbit spinal cords after 15 minutes of transient ischemia until 7 days of the reperfusion. After the 15-minute ischemia, there was a significant decrease of neurologic scores in the ischemic group compared with the sham-operated control group at 7 days of reperfusion (P = 0.0017), and the majority of motor neurons was selectively lost at 7 days of reperfusion (P = 0.0039). NO2-Tyr was transiently induced at 8 hours of reperfusion in the ventral part of the spinal cord (0.47%+/-0.86%, NO2-Tyr/total tyrosine; P = 0.0021), but was not induced at any time point of reperfusion in the dorsal part of the spinal cord. Strong immunoreactivity for NO2-Tyr was selectively induced in large pyramidal motor neurons at 8 hours of reperfusion and was still weakly present until 7 days of reperfusion. (There may be a difference in sensitivity between the two techniques.) These results suggested that protein tyrosine nitration by nitric oxide plays a role in the selective motor neuron cell damage after transient spinal cord ischemia.

Animals↗

PubMed1998

Apoptosis of motor neurons with induction of caspases in the spinal cord after ischemia.

BACKGROUND AND PURPOSE: Some neuronal subpopulations are especially vulnerable to ischemic injury. In the spinal cord, large motor neurons are vulnerable to ischemia and are selectively lost after transient ischemia. However, the mechanisms of the neuronal loss have been uncertain. We hypothesized that spinal motor neurons might be lost by apoptosis and investigated a possible mechanism of neuronal death by detection of double-strand breaks in genomic DNA and immunohistochemical analysis for caspases, ie, interleukin-1beta converting enzyme (ICE), Nedd-2, and CPP32. METHODS: We used a rabbit spinal cord ischemia model created with a balloon catheter. The spinal cord was removed at 8 hours, 1, 2, or 7 days after 15 minutes of transient ischemia, and histological changes were studied with hematoxylin-eosin staining. To detect double-strand breaks in DNA, a staining with terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL) was performed. Furthermore, expression of ICE, Nedd-2, and CPP32 was investigated by Western blotting and immunohistochemical analysis. RESULTS: Motor neurons were selectively lost at 7 days after transient ischemia. TUNEL study demonstrated that no cells were positively labeled until 1 day after ischemia, but nuclei of some motor neurons were positively labeled at 2 days. Western blot analysis revealed no immunoreactivity for ICE and slight immunoreactivities for Nedd-2 and CPP32 in the sham-operated spinal cords. However, immunoreactivity became apparent at 8 hours after transient ischemia, decreased at 1 day, and returned to baseline level at 2 days. Immunohistochemical analysis demonstrated that motor neurons were responsible for induction of those caspases. CONCLUSIONS: Double-strand breaks in genomic DNA and induction of three caspases were demonstrated. These results indicate that motor neuron death in the spinal cord after transient ischemia is profoundly associated with activation of apoptotic processes.

Animals↗

PubMed1998

Outcome of medically treated Stanford type B aortic dissection.

Optimal treatment for patients with uncomplicated type B dissection remains a matter of debate. From January, 1987, through June, 1996, 43 patients with acute type B dissection were treated exclusively by medical therapy according to our management guidelines. After discharge, aortography and enhanced computed tomography were performed every 6 months to evaluate the diameter of the dissected aorta. All 43 patients survived the acute phase and were discharged alive from the hospital. There was no death related to aortic dissection. Three patients underwent surgical treatment in the chronic phase because of aortic enlargement. Aortic enlargement in 3 additional patients was managed medically. The values for freedom from aortic enlargement for 43 patients at 1, 3, and 5 years were 100%, 91%, and 86%, respectively. The long-term survival rates of patients treated medically and discharged from the hospital are acceptable.

Aged↗

PubMed1998

Assessment of the Björk-Shiley prosthetic valve orifice area in the aortic position.

The actual orifice area of a valve is still considered to be a valuable index for assessing prosthetic valve function. Valve orifice area as calculated by Gorlin's formula is, however, not constant but changes in proportion to the transvalvular flow rate. The purpose of the present study was to examine the relationship between orifice area and flow rate across the Björk-Shiley prosthetic valve as calculated by Gorlin's formula, and to modify the formula in a series of patients with the Björk-Shiley prosthetic valve in the aortic position. Fifty-six patients who had received aortic valve replacement with a Björk-Shiley prosthetic valve underwent cardiac catheterization. Prosthetic valve orifice area was calculated by Gorlin's formula and then plotted against flow rate across the valve with respect to valve size. The relationship between orifice area and flow was linear. The discharge coefficient of Gorlin's formula was plotted against flow rate, and a linear correlation was obtained. By substituting Gorlin's formula for an empiric coefficient into the function for transvalvular flow rate, a modified formula that can predict the actual orifice area of the prosthetic valve is obtained.

Aortic Valve↗

PubMed1998

Replacement of the ascending aorta and aortic valve with a composite graft: operative and long-term results.

The purpose of this study is to analyze our treatment experience on patients with ascending aortic aneurysms, with aortic regurgitation. From January 1974 to December 1995, 49 patients underwent replacement of the aortic valve and ascending aorta with a composite graft, in which primary operation cases were 44 and reoperation ones were 5. The Bentall technique was used in 20 patients, the button technique in 11, the interposition graft technique in 11, and a combination of the interposition graft and button technique in 7. All but one reoperation cases underwent the interposition graft technique. Hospital mortality was 30% for the Bentall technique, and 9.1% for the button technique and 9.1% for the interposition graft technique; there was no hospital mortality in the combination of the interposition graft and button technique. Hospital mortality of interposition graft technique in primary operation cases was 9.1%, and that in reoperation cases was 0%. Hospital mortality in patients underwent from 1974 to 1985 was 30.8%, 27.8% from 1986 to 1991, and 0% from 1992 to 1995. Five late deaths occurred in the Bentall group (35.7%) and one late death in the button technique (9.1%). Not late deaths in the other groups have occurred. In summary, operative mortality in Bentall technique group was higher than that of the other groups. Operative results were improved by the change of operative methods. The interposition graft technique is preferable for patients undergoing reoperation or when tension on the ostial anastomoses may occur. The button technique is best for patients with aortic dissection or inflammation involving the coronary ostia.

Adult↗

PubMed1998

[Brain damage following aortic arch repair with regard to techniques of selective cerebral perfusion and preoperative cerebral lesions].

One hundred and twenty-nine aortic aneurysm patients (true 68 and dissection 61) underwent aortic arch repair from January 1987 to December 1995. Postoperative brain damage was evaluated regarding both preoperative brain lesions and techniques of selective cerebral perfusion (SCP) in that one pump for SCP until April 1992, then two pumps were employed, one for right and the other for left hemisphere of the brain. Overall hospital mortalities were 21% in true and 13% in dissecting aneurysms. Ten patients were complicated with postoperative brain damages (coma 8 and hemiplegia 2), registering 7.8% of total patients. Both history of stroke and silent cerebral infarction (SCI) detected by CT and/or MRI were considered to be positive in the mean of having preoperative brain lesions. Although there was no significant difference between incidences of postoperative brain damage in true and dissecting aneurysms, registering 11% and 4% respectively, preoperative brain lesions in true aneurysm (68%) was significantly greater than dissecting aneurysm (32%). Furthermore, the incidence of postoperative brain damage was 22% in one-pump SCP which was significantly greater than 3% in two-pumps SCP in the patients with a true aneurysm. But there was no postoperative brain complication in patients with SCI even using either one two pumps for SCP. The present data suggest two-pumps SCP is better technique for cerebral protection compared to one-pump SCP for aortic arch repair.

Adult↗

PubMed1998

Sutureless ringed graft replacement of descending thoracic aorta with extensive calcification.

A 79-year-old hypertensive woman, with fusiform shaped atherosclerotic aneurysm in the descending thoracic aorta whose medial layer was maintained by an extensive solid calcium plate (porcelain aorta), was successfully treated using a sutureless intraluminal ringed graft. Spools of the ring were fixed by circumferential ligatures at both proximal and distal sites of anastomosis and a dilated segment of the aorta was replaced with the tube graft.

Aged↗

PubMed1998

Development of total artificial heart with economical and durability advantages.

To develop a total artificial heart (TAH) pump system, we created a design paying particular attention to durability and cost. We adopted a pneumatically driven sac type artificial heart, where the configuration of the sac was decided according to the methodology of flow visualization. Its configuration is almost round to achieve as little stagnation as possible and a low turbulent flow. The main body of the sac was made using polyvinyl chloride (PVC) paste. The paste was poured into an external mold, and heated in a hot air drying oven. Coating was performed using polyurethane. The basic performance of this pump system was tested using a model circulation circuit, and a fitting study through acute animal experiment, using a healthy adult goat, was carried out. As for the TAH produced experimentally, a pump output exceeding 5.0 l/min in the model circulation circuit was provided. Implantation in the internal pleural cavity of a healthy adult goat, 55 kg in weight, proved possible and quite easy in comparison. It is thought that a more refined design in the connector part is desirable. Furthermore, a chronic experiment with the TAH will be carried out, and examination will need to be repeated in the future.

Animals↗

PubMed1998

Monitoring system for the totally implantable ventricular assist system by use of sensors for virtual reality.

For the development of the totally implantable artificial organs, it is an important problem to monitor the conditions of the implantable devices, especially when used in clinical cases. In this study we used position sensors for the 3-dimensional (3-D) virtual reality (VR) system monitor an implantable artificial heart. The sensors used in the experiments were 3-space Fastrak (Polhemus, USA). The position sensors using electro-magnetic forces were attached to the inner actuating zone. Sensitivity of the position sensors was in the order of around 0.8 mm. By use of these VR position sensors, we could easily detect the six degrees of freedom as x,y,z, and pitch, yaw, roll of these sensors. Experimental evaluation using a model circulation loop and healthy adult goats was performed. Experimental results suggest that our newly developed implantable sensors for monitoring the implantable artificial heart system were useful for sensing driving condition, thus possibly useful for the implantable devices for clinical usage.

Animals↗