Biomedical subjects

Tomoaki Jikuya

Publications and source records attributed to Tomoaki Jikuya.

16 recordsLinked to original sources

PubMed2006

Excision after chemoradiotherapy of invasive thymoma extending into the right atrium: report of a case.

We report a case of invasive thymoma with intracardiac extension, resulting from the progression of intracaval growth, in a 56-year-old woman. Initially, the patient received two courses of chemotherapy, but the tumor showed only a modest response; however, subsequent radiotherapy reduced the tumor size further and the intracardiac lesion disappeared, making it possible to excise the tumor without cardiopulmonary bypass. Thus, when a thymoma does not respond well, we recommend radiotherapy as another treatment option, because its effects may allow for less invasive and more complete tumor excision.

Combined Modality Therapy↗

PubMed2006

Comparison of hydroxyl radical generation in patients undergoing coronary artery bypass grafting with and without cardiopulmonary bypass.

We measured the hydroxyl radical (.OH) generation in fourteen patients undergoing coronary artery bypass grafting (CABG), of whom seven patients underwent on-pump CABG with cardiopulmonary bypass (CPB) and seven patients underwent off-pump CABG without CPB. To detect .OH generation, we measured the urinary excretion of .OH products of creatinine (Cr), creatol (CTL; 5-hydroxycreatinine) and methylguanidine (MG) with HPLC using the one point sampling and collected urine during and after the operation. The urinary CTL value corrected urinary Cr value of on-pump CABG significantly increased about 3-5 times from the beginning of CPB to 4 h after operation compared to the baseline value before CPB in both the collected urine and the one point sampling urine. The urinary MG/Cr value in both groups did not change significantly. Significantly increased .OH generation was found during and soon after on-pump CABG.

Aged↗

PubMed2005

The hemolytic characteristics of monopivot magnetic suspension blood pumps with washout holes.

The hemolytic characteristics of monopivot magnetic suspension blood pumps as a function of impeller washout hole configuration and female pivot shape are observed. The pump impellers are designed with three washout hole configurations for blood circulation, and four female pivot shapes to reduce blood stagnation and to enhance antithrombogenicity. The hemolytic characteristics of the monopivot pumps were observed to be better than those of a currently available commercial centrifugal blood pump, BP-80, and changed to be nearly equal when the female pivot shape was changed. This indicates that hemolysis in monopivot pumps is mainly caused by shear stress between the male and female pivots.

Animals↗

PubMed2004

Severely calcified intravenous leiomyomatosis with cardiac extension.

Intravenous leiomyomatosis is a rare benign tumor. In this report we described a case of 72-year-old female who presented with a tumor of this type. Thirty years earlier she had received hysterectomy for uterine myoma. Echocardiography, computed tomography, and inferior vena cavography revealed an intracardiac tumor with calcification arising from the left internal iliac vein. A simultaneous operation was performed successfully with a median sternotomy and left retroperitoneal approach under cardiopulmonary bypass support. Histopathological examination revealed that the resected tumor was a calcified intravenous leiomyoma with cardiac extension. This case showed the three interesting features compared with other reports. Among all reported cases of intravenous leiomyomatosis, this patient and another were the oldest at 72 years old, severe calcification of intravenous leiomyomatosis was infrequent, and the delay (30 years) from hysterectomy to removal of the intracardiac tumor was the longest.

Aged↗

PubMed2004

High-frequency QRS potentials as a marker of myocardial dysfunction after cardiac surgery.

BACKGROUND: High-frequency QRS potentials are sensitive to myocardial ischemia. The aim of this study was to evaluate the usefulness of high-frequency QRS potentials as a marker of myocardial dysfunction after cardiac surgery. METHODS: Seventy patients undergoing coronary artery bypass grafting or heart valve surgery were involved. High-frequency QRS potentials were measured by signal-averaged electrocardiogram, and calculated as the root-mean-square voltage of the total QRS duration (RMST). The postoperative RMST was expressed as a percentage of the preoperative RMST. The mean RMST at 1 to 2 hours after removing the aortic cross-clamp was compared with the cardiac index, inotropic agents, and aortic cross-clamping time. The occurrence of ventricular tachycardia within 24 hours and the RMST at 2 postoperative days were also evaluated. Patients were divided into quartile groups from highest to lowest at postoperative RMST (groups 1, 2, 3, and 4, respectively, from maximum to minimum). RESULTS: In postoperative states, cardiac index significantly decreased in accordance with the RMST decrease in a stepwise manner, although there were no differences in cardiac index among the four groups preoperatively. Inotropic agents and aortic cross-clamping time increased as RMST decreased. A high rate of ventricular tachycardia within 24 hours and delayed RMST recovery at 2 postoperative days were seen in group 4. The curve of sensitivity and specificity showed that severe reduction (threshold, 35%) of RMST indicated low-output syndrome. CONCLUSIONS: The severe reduction of filtered high-frequency QRS potentials was related to myocardial dysfunction. Measurement of filtered high-frequency QRS potentials could become a useful, noninvasive, real-time monitor of myocardial dysfunction after surgery.

Cardiac Output, Low↗

PubMed2004

Cerebral metastasis from angiosarcoma of the aortic wall: case report.

BACKGROUND: Primary or metastatic cerebral angiosarcoma is extremely rare, and only limited cases have been reported. The authors here describe a case of angiosarcoma, which was initially identified and diagnosed by the cerebral metastatic lesion; later examinations suggested that the primary site was the abdominal aorta. CASE DESCRIPTION: A 53-year-old man, who had suffered an abdominal aortic aneurysm 2 months earlier, experienced a sudden onset of left-sided hemifacial convulsion and dysarthric speech. Computed tomography (CT) showed a hemorrhagic mass lesion with perifocal edema in the right frontal lobe. Magnetic resonance imaging (MRI) showed a regionally marked hypointensity in the mass lesion on both T1- and T2-weighted images, which might suggest hemosiderin deposition. The tumor was removed in its entirety. Pathologic examination revealed an old hematoma with a hemosiderin deposit containing markedly atypical tumor cells, and angiosarcoma was diagnosed. Resection of the abdominal aortic aneurysm and iliac bone biopsy were performed and angiosarcoma was recognized in each surgical specimen. Based on clinical and pathologic findings, the primary site was considered to be the abdominal aorta. CONCLUSIONS: Clinicians should be aware of this rare histologic type of tumor. Unique MRI findings such as those obtained in our case might be useful for differentiating this condition from other intracranial neoplasms.

Aorta, Abdominal↗

PubMed2004

Resonant frequency control for artificial heart using online parameter identification.

To develop effective medical care and therapeutic control using an artificial heart, a new control method has been developed. This new method can control the artificial heart effectively and can adapt to internal physiological behavior using measured physiological data; aortic pressure, aortic flow, and pump flow. This method consists of first, a second-order physiological model, which represents the internal physiological behavior by a mathematical equation; and second, an estimation method, which can identify the physiological parameters; aortic inertia, aortic resistance, aortic compliance, and peripheral resistance by a parameter identification method. It can then calculate the resonant frequency as the control signal for the artificial heart from the identified physiological model. To confirm the effectiveness, the proposed method was evaluated in a computer simulation study. This evaluation showed that the new method could estimate the physiological parameters and the resonant frequency within a 10% error. The impedance of the systemic circulation could also be reduced by this method.

Algorithms↗

PubMed2004

The most profitable use of flow visualization in the elimination of thrombus from a monopivot magnetic suspension blood pump.

The purpose of this study was to eliminate fluid dynamic causes of thrombus formation for the monopivot magnetic suspension centrifugal pump under development with the aid of flow visualization as an indirect measurement tool for animal experiments. The formation of thrombus observed in early animal experiments was successfully overcome by combining the multiple washout holes at the center into a single hole, optimizing the hole diameter, and eliminating the pivot gap. Flow visualization was used to optimize the washout hole diameter influencing the flow around the pivot. In animal experiments flow visualization showed that the contours of thrombus corresponded to shear rates of 300 s(-1) or 1300-1700 s(-1). It was found that flow visualization is a useful technique to predict locations where low shear thrombi form and to optimize the pump design in the development stage.

Animals↗

PubMed2003

Complex intimal flaps in acute aortic dissection.

A 43-year-old man was emergently admitted and diagnosed as acute aortic dissection (Stanford type A). While being prepared for emergent operation he fell into hemodynamic hazard with repeated ventricular fibrillation and loss of consciousness. Massive aortic regurgitation and coronary disturbance due to a back-and-forth movement of an intimal flap through the aortic valve were the causes of the cardiogenic catastrophy. In addition, a completely torn intimal flap was intussuscepted into the origin of the brachiocephalic artery. This was thought to disturb the cerebral perfusion. Acute aortic dissection with such complex intimal flaps is very rare. In such cases cardiopulmonary bypass should be established to maintain the patient's cardiac function as soon as possible after diagnosis and the operation should be performed with sufficient brain protection.

Acute Disease↗

PubMed2003

ONO-6818, a novel, potent neutrophil elastase inhibitor, reduces inflammatory mediators during simulated extracorporeal circulation.

BACKGROUND: Among the serine proteases, neutrophil elastase is a powerful cytotoxic enzyme and plays a pivotal role in the inflammatory response associated with cardiopulmonary bypass. This study assesses the effects of the specific inhibition of neutrophil elastase by a novel, potent, low-molecular-weight neutrophil elastase inhibitor, ONO-6818. We hypothesized that ONO-6818 reduces inflammatory mediators and modulates adhesion molecules and the deformability of neutrophils during simulated extracorporeal circulation. METHODS: Simulated extracorporeal circulation was established by recirculating fresh heparinized (3.75 U/mL) human blood for 120 minutes in a membrane oxygenator and a roller pump with and without 1.0 micromol/L of ONO-6818 (n = 9 for control group, n = 7 for ONO-6818 group). The neutrophil adhesion molecules, CD11b and L-selectin, and the cytoplasmic F-actin of neutrophils were measured by flow cytometry. Neutrophil deformability was evaluated using simulated silicon microcapillaries. Neutrophil elastase, interleukin 8, and C5b-9 were measured using enzyme immunoassay. RESULTS: Neutrophil elastase levels were significantly lower in the ONO-6818 group. ONO-6818 significantly reduced interleukin 8 and C5b-9 production. ONO-6818 did not modulate changes of CD11b and L-selectin during recirculation. Cytoplasmic F-actin content and changes of neutrophil deformability did not significantly differ between the groups. CONCLUSIONS: Inhibition of neutrophil elastase activity with ONO-6818 reduces further interleukin 8 production and the formation of the complement membrane attack complex, and this results in a reduction of neutrophil elastase levels during simulated extracorporeal circulation. This study suggests that specific neutrophil elastase inhibition with ONO-6818 is a feasible therapeutic option to attenuate the exaggerated inflammatory response associated with cardiopulmonary bypass.

Actins↗

PubMed2003

Tsukuba remote monitoring system for continuous-flow artificial heart.

In order to make long-term medical treatment with the use of an artificial heart effective, we developed the Tsukuba remote monitoring system, which enables medical staff to manage the physiological condition of patients and the driving condition of the artificial heart at anytime from a remote place. This remote monitoring system has three functions: first, a remote monitoring function, which enables medical staff to monitor measured data from a remote place anytime by using not only a personal computer but also a cellular phone; second, an analyzing function, which estimates the unmeasured physiological behavior in the body based on a mathematical physiological model; and third, a warning function, which detects physiological problems and malfunction of the artificial heart by applying the if-then rule and sends a warning message to the medical staff. As a result of applying this system to animal experiments, we have confirmed the effectiveness of the proposed system.

Animals↗

PubMed2002

Cystic tumor of the atrioventricular nodal region.

We report a case of a 66-year-old female who presented exertional dyspnea and palpitation. Echocardiography, transesophageal echocardiography and computed tomography showed a right atrial cystic mass attached to the interatrial septum. The patient underwent successful excision of the mass. The histopathological findings confirmed the lesion as a cystic tumor of the atrioventricular nodal region. This is the third known case of this condition diagnosed antemortem and treated successfully with surgical excision.

Aged↗

PubMed2002

On-line parameter identification of systemic circulation using the delta operator.

To develop effective medical care with the artificial heart, we propose a new method, on-line parameter identification of the systemic circulation using the delta operator which can calculate the time-varying and unmeasured hemodynamics of the internal human body from some measured data: aortic pressure and total flow in real time. This method consists of first, a dynamic physiological model which is configured with the physiological parameters Ca (aortic compliance) and Rp (total peripheral resistance); and second, a system identification method using the delta operator. In the computer simulation study, we could confirm the effectiveness to identify the physiological parameters. In animal experiments with a left ventricular assist system, the physiological parameters, Ca = 1.8 (ml/mm Hg) and Rp = 0.8 (mm Hg s/ml), could be identified on-line.

Adaptation, Physiological↗

PubMed2002

Online parameter identification of second-order systemic circulation model using the delta operator.

To develop effective medical care with the artificial heart, we proposed a new method that can calculate the time varying and unmeasured hemodynamics of the human body from measured physiological data: aortic pressure, aortic flow, and pump flow in real time. This method comprises first, the second order of systemic circulation model, which consists of aortic compliance (Ca), aortic resistance (Ra), aortic inertia (L), and total peripheral resistance (Rp); and second, system identification using the delta operator. In the computer simulation, we confirmed the effectiveness of this method. During the animal experiment with the left ventricular assist system, the physiological parameters could be identified online: mean Ra = 0.04 mm Hg s/ml, mean Ca = 0.65 mm Hg/ml, mean L = 0.004 mm Hg s(2)/ml, and mean Rp = 0.3 mm Hg s/ml. This new method efficiently identified the physiological parameters, which are important not only to support the medical care but also to develop the control method adapted to the physiological behavior.

Animals↗

PubMedDate not supplied

Fractural characteristic evaluation of a microcapsule suspension using a rotational shear stressor.

We are developing microcapsule suspensions to evaluate the absolute hemolytic properties of centrifugal blood pumps. Four types of microcapsule suspensions, with maximum diameters of 100 microm or 10 microm, and membranes of polyurethane or melamine resin, were exposed to fluid dynamic shear up to 15,000 s(-1) with a rotating shear stressor developed in our laboratory. As a result, destruction was observed of only the 100 microm microcapsules. The microcapsules with polyurethane membranes broke at a high shear velocity range over 11,250 s(-1), a tendency similar to that observed using bovine blood. The microcapsules with melamine resin ruptured at approximately 7,500 s(-1). These observations could lead to determination of absolute hemolysis from shear stress occurring in centrifugal blood pumps.

Biomechanical Phenomena↗

PubMedDate not supplied

Development of built-in type and noninvasive sensor systems for smart artificial heart.

It is very important to grasp the artificial heart condition and the physiologic conditions for the implantable artificial heart. In our laboratory, a smart artificial heart (SAH) has been proposed and developed. An SAH is an artificial heart with a noninvasive sensor; it is a sensorized and intelligent artificial heart for safe and effective treatment. In this study, the following sensor systems for SAH are described: noninvasive blood temperature sensor system, noninvasive blood pressure sensor system, and noninvasive small blood flow sensor system. These noninvasive sensor systems are integrated and included around the artificial heart to evaluate these sensor systems for SAH by the mockup experiments and the animal experiments. The blood temperature could be measured stably by the temperature sensor system. Aortic pressure was estimated, and sucking condition was detected by the pressure sensor system. The blood flow was measured by the flow meter system within 10% error. As a result of these experiments, we confirmed the effectiveness of the sensor systems for SAH.

Animals↗