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Biomedical subjects

S Nitta

Publications and source records attributed to S Nitta.

At least 145 records · Page 8Linked to original sources
PubMed1991

Postganglionic sympathetic nerve activity with correlation to heart rhythm during left ventricular assistance.

In order to evaluate the effect of ventricular assist device (VAD) driving on the autonomic nervous system, sympathetic neurograms during left ventricular (LV) assistance were analyzed by power spectrum and coherence function. Our TH-7B pneumatically-driven sac-type VAD was used in seven adult mongrel dogs. VADs were inserted between the left atrium and the descending aorta. Renal sympathetic nerve activity (RSNA) was detected by use of bipolar electrodes attached to the left renal sympathetic nerve via a retroperitoneal approach. Values of squared coherence between the arterial pulse wave and RSNA were measured at the same frequency of cardiac and VAD pumping rhythms. During LV assistance, coherence at the cardiac rhythm frequency was decreased, and coherence at the VAD pumping rhythm frequency was increased. These results indicate that the arterial pulse wave, which was produced by the VAD assistance, contributed to postganglionic sympathetic nerve activity.

Animals↗
PubMed1991

Silent obstruction of the coronary stenosis between diagnostic angiography and later percutaneous transluminal coronary angioplasty without myocardial infarction.

Among 204 patients with severe coronary artery stenosis amenable to percutaneous transluminal coronary angioplasty (PTCA), 5 (2.5%) developed new silent total coronary occlusion of the vessel to be dilated without any chest symptom during the period between diagnostic coronary angiography and repeat coronary angiography at the time of the operation. We evaluated the clinical and angiographical characteristics of the patients with silent obstruction of the coronary artery in a short time, compared with the patients with unstable angina pectoris, who is considered to be suffering from acute myocardial infarction with severe chest symptom. None of the clinical variables studied showed a significant difference between the two groups. Among the angiographic variables, the degree of collateral was higher and impaired coronary perfusion distal to the lesion was more frequently found in unstable angina group. These results suggest that unstable angina is in a later stage of the ischemic heart disease compared with the time of the diagnostic angiography in patients with silent obstruction. Silent obstruction of high degree coronary stenosis is presumably due to the development of collateral circulation.

Aged↗
PubMed1991

Spectral analysis of the renal sympathetic neurogram during left ventricular assistance.

To assess the effect of left ventricular assistance on cardiac-related sympathetic nerve activity, renal sympathetic nerve activity was analysed using power spectrum and coherence function. Our TH-7B pneumatically driven sac type Ventricular Assist Device (VAD) was used in the acute experiment of 7 adult mongrel dogs. VAD were inserted between the left atrium and the descending aorta as left heart bypass. RSNA was detected by use of the bipolar electrodes attached to the left renal sympathetic nerve. Values of squared coherence between the arterial pulse wave and RSNA were measured at the cardiac rhythm and VAD pumping rhythm. Before the left ventricular assistance, coherence at the cardiac rhythm and the pumping rhythm were 0.62 +/- 0.15, 0.23 +/- 0.18 (mean +/- SD), respectively. With the VAD pumping, these values became 0.09 +/- 0.05, 0.53 +/- 0.20, respectively. These results indicate that arterial pressure wave which was created by the VAD assistance contributed to the post ganglionic sympathetic activity.

Animals↗
PubMed1991

Development and evaluation of the vibrating electromagnetically-driven artificial heart.

An vibrating electromagnetically driven univalved artificial heart was newly developed in our team. The fluid mechanical, hematological, and hemodynamical properties of this pump was evaluated in the moc circulation and animal experiments using adult goats. This vibrating electromagnetic (VEM) pump could generate more than 101/min with 10 Hz vibration, and could obtain the 2 kinds of flow and pressure patterns, such as constant peak and periodical peak patterns. The values of free Hb showed within acceptable values. We concluded that this pump is useful for totally implantable artificial heart.

Animals↗
PubMed1991

TH-7B pneumatically driven sac-type ventricular assist device and drive system.

TH-7B pneumatically driven sac-type ventricular assist device and drive system including automatic control system were developed and evaluated in the chronic animal experiments. The blood-contacting surfaces of the blood pump are coated with either Cardiothane or Cardiomat. In the chronic experiments using adult goats, only one of fifteen goats showed sudden thrombus formation after 34 pumping days. No gross findings of thrombus formation were observed in any of the cases, except for a thin circular thrombus at the junction of the connectors and the sac of the blood pump. These results suggest that antithrombogenicity of this system was satisfactory for clinical use.

Animals↗
PubMed1991

Development of the total artificial heart control system.

Sympathetic neurogram is potentially useful for the real time total artificial heart (TAH) control system. In this study, we used sympathetic tone and hemodynamic derivatives to prospect the following cardiac output in acute animal experiments using adult mongrel dogs. Moving averages of the mean left atrial pressure and mean aortic pressure were used as the parameters of the preload and afterload, respectively. Renal sympathetic nerve activity (RSNA) was also utilized as the parameter of the sympathetic tone. Equation which prospect the following cardiac output was calculated using the multiple linear regression analysis of the time series data in adult mongrel dogs. A significant correlation was observed between the prospective and following measured cardiac output. These results suggest the potential usefulness of the sympathetic neurogram for the real time TAH automatic control system.

Animals↗
PubMed1991

Coherence function between sympathetic neurogram and arterial pulse wave in animal with total artificial heart.

To assess the influence of the total artificial heart replacement on autonomic nervous system, sympathetic neurogram was analyzed by power spectrum and coherence function. Two pneumatically driven sac-type ventricular assist devices were implanted as biventricular bypass (BVB) in adult mongrel dogs. After the BVB pumping, natural heart was electrically fibrillated to constitute the BVB type TAH model. Renal sympathetic nerve activity (RSNA) was recorded using the bipolar electrode attached to the left renal sympathetic nerve. RSNA was amplified and integrated by the use of R-C integrator. Power spectra of the RSNA and the values of squared coherence between the arterial pressure waveform and the RSNA were calculated by the computer system. In animal with TAH, coherence at the cardiac rhythm frequency was decreased, and coherence at the TAH pumping rhythm frequency was increased. These results indicate that the arterial pulse wave which was observed in TAH animal contributed to sympathetic neurogram.

Animals↗
PubMed1991

Clinical application of the ventricular assist devices in Japan.

From 1980 to March in 1989, there were 177 clinical application of ventricular assist device in Japan. Original diseases were 50% ischemic heart disease and 37% valvular disease. Duration of assistance ranged from one hour to 70 days. Thirty-one cases weaned from ventricular assistance and 11 cases became long-time survivors.

Cause of Death↗
PubMed1991

[Perioperative cardiac complications of pulmonary operations in patients with/without coronary stenosis].

It has been suggested that the presence of ischemic heart disease correlates with an increased risk of cardiac infarction and fatal arrhythmia following noncardiac operations. To prevent these complications, coronary arteriographies were performed on 55 patients before pulmonary surgery for the assessment of the risk of perioperative cardiac complications. A coronary artery obstruction, with a 50% or greater reduction in the internal diameter was recognized on 21 patients (Group 1) and the other 34 patients showed no significant coronary stenotic lesions (Group 2). Discriminant analysis revealed that cardiac index (p less than 0.025), blood sugar level (p less than 0.05), hyperlipidemia (p less than 0.05) and postoperative cardiac failure (p less than 0.005) correlated independently with coronary artery stenosis. Postoperative cardiac complications were observed in the form of atrial arrhythmias (11%), ventricular arrhythmias (16%) and ischemic ECG findings (17%) in all cases. The rate of occurrence of these complications were not different between the two groups. However, the need for therapeutic procedures for perioperative circulatory failure (18%) was much greater in group 1 (p less than 0.005). This study supports the merits of preoperative coronary arterial angiography and the estimation of the left ventricular function in reducing pulmonary perioperative risk.

Aged↗
PubMed1991

[A case of bronchial anastomotic stenosis after right upper sleeve lobectomy treated with silicone stent].

A case treated with silicone stent for bronchial granulomatous stenosis caused by anastomosis after right upper sleeve lobectomy was reported. A 68-year-old man complained of atelectasis of right upper lobe due to squamous cell carcinoma was admitted to our department. We performed right upper sleeve lobectomy. Four weeks after the operation, hemoptysis and dyspnea appeared with developing local empyema. We performed closure of pleural fistula and thoracoplasty, however, did not improve the symptoms. We performed tracheotomy for deteriorating dyspnea. In addition, granulomatous stenosis of bronchial anastomotic site was observed endoscopically. We tried to insert silicone stent into stenotic site. Although, first trial was in failure, we modified the design of the stent and succeeded in fixation of the stent. The airway was completely re-opened and good patency had been maintained for 7 months until his death due to pneumonia.

Aged↗
PubMed1991

Sympathetic nerve activity during maintaining circulation with only left ventricular assist device.

Maintaining circulation with an left ventricular assist device (LVAD) alone during cardiac arrest until heart transplantation, was evaluated by the use of the sympathetic neurogram. To evaluate the influences of this method on autonomic nervous system, sympathetic neurogram was analyzed by power spectrum and coherence function. In acute animal experiments using mongrel dogs, LVAD were implanted. After the LVAD implantation, ventricular fibrillation was induced electrically. Renal sympathetic nerve activity (RSNA) was detected by the use of bipolar electrodes attached to the left renal sympathetic nerve. Values of squared coherence between the arterial pulse wave and RSNA were calculated. Under the condition of circulatory maintenance with LVAD, coherence at the cardiac rhythm frequency was decreased, and coherence at the LVAD pumping rhythm frequency was increased. These results suggest that the arterial pressure which was observed during maintaining the circulation with only LVAD contributed to sympathetic neurogram.

Animals↗
PubMed1991

Hydrodynamic endurance test of the prosthetic valve used in the various types of the ventricular assist device.

To evaluate the various basic designs of the pump chambers used in the ventricular assist devices (VADs), hydrodynamic endurance test was performed from the viewpoint of the durability of the prosthetic valves used in the VAD. For the hydrodynamic analysis, we designed three basic types of pump (sac type, diaphragm type, and pusher plate type) using the same material and having the same capacity and shape. Prosthetic valves in these VADs were tested from the standpoint of the water hammer effect, which affects the valve durability, to determine which pump design would be most durable as a prosthetic valve in the VAD. The water-hammer phenomenon was evaluated using the maximum pressure gradient (MPG) across the prosthetic valve in the moc circulatory loop. Maximum pump output was recorded when we used the diaphragm type model, and minimum MPG in the commonly used driving condition of the VAD were recorded when we used the sac type model. The results suggest that the sac type VAD model is the most durable design for the prosthetic value.

Adult↗
PubMed1991

Development and clinical evaluation of the long time digital Holter ECG system using non-tracking technology.

Newly developed long time digital Holter ECG system utilizing a stamp-size non-tracking (NT) tape which can be used for 192 hours as 2ch recording, was evaluated in the clinical cases. The system has employed newly developed VLSIs and NT technology which enables to obtain reliable long time recording with smaller and lighter Holter system of ECG and variety of biological signals. The results indicated that good data reproduction was shown in this system.

Adult↗
PubMed1991

Systemic circulation with high frequency blood flow--analysis from neurophysiological point of view.

The vibrating electromagnetically driven univalved artificial heart, which provided more than 10 1/min at 10 Hz/sec. vibration, was developed in our team. This vibrating electromagnetic pump (VEMP) produced the original flow pattern compared with the flow pattern of the natural heart, so that circulatory regulatory system during maintain the circulation with VEMP must be investigated before the clinical application. In order to assess the effect of high frequency blood flow produced by the VEMP from the neurophysiological point of view, power spectral analysis of the hemodynamics was performed. VEMP was implanted as the total left heart bypass in adult goats and right heart circulation was maintained by natural hearts. In arterial blood pressure during maintain circulation by the high frequency blood flow, Mayer waves (0.01-0.15 Hz) were significantly decreased, though respiratory waves (0.25-0.40 Hz) were not significantly changed. These results suggest that circulatory regulatory system was influenced by the high frequency blood flow produced by the VEMP.

Animals↗
PubMed1991

Long-time inflation of the PTCA balloon.

For patients for whom the conventional percutaneous transluminal coronary angioplasty (PTCA) did not adequately improve stenosis, or sufficient angioplasty was impossible because of occurrence of dissection, we attempted using a long-time balloon inflation for more than 10 minutes. In order to allow the use of this balloon, we instituted an active rehabilitation program using a bicycle ergometer to promote the development of the collateral circulation up to the time of performing diagnostic angiography and PTCA, while attempting to use a perfusion balloon catheter for those patients not developing sufficient collateral circulation. Of the 134 patients undergoing PTCA, unsatisfactory angiographic results were obtained in 13 patients. Of these patients, long-time balloon inflation was performed in seven and primary success was achieved in six. From this study, we believe that the long-time balloon inflation in PTCA can improve the primary success rate and reduce postoperative complications.

Angina Pectoris↗
PubMed1991

[A case of pulmonary coccidioidomycosis].

A 55-year-old Japanese woman was admitted to our hospital, complaining of flu-like symptoms and left-sided chest pain. Her chest X-ray films revealed a solitary coin lesion in the left middle lung field. She had traveled to California and Arizona 3 months before being taken ill. Because of negative result in sputum cytology and trans-bronchial lung biopsy examination, open lung biopsy and wedge resection was performed. Histological examination revealed endosporulating spherules in a caseous lesion of the epithelioid granulomas, and fungal cultures demonstrated barrel-shaped arthropores. Pulmonary coccidioidomycosis was diagnosed. Coccidioidomycosis is a rare fungal disease found in certain endemic areas in the southwestern region of the United States. She had been infected during her travels in America, and this is the second case in Japan who had taken surgical intervention for pulmonary coccidioidomycosis.

Coccidioidomycosis↗
PubMed1991

[ECMO treatment for ARDS].

Between February 1988 and March 1990, ECMO was performed (veno-arterial perfusion; 3 cases, venovenous; one case) is 4 ARDS patients. However no patient could be weaned from ECMO (32-80 hours) and all died. The causes of deaths were attributed to the complications of ARDS itself that existed before ECMO therapy and ECMO was highly effective in providing temporally life support. We consider that entry criteria of ECMO should not be based on gas exchange alone and that lung compliance and circulatory insufficiency should be taken into account.

Adult↗