The science reports of the research institutes, Tohoku University. Ser. C, Medicine. Tohoku Daigaku最新文献

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.

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.

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.

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.

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.

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.

Alzheimer disease and multi-infarct dementia are two entirely different diseases producing almost the same abnormalities as dementia syndrome. The statistical studies with MRI to locate the focus of dementia syndrome in the neocortex was an absolute failure. With MRI there is drastic atrophy and destruction of the amygdala and hippocampus suggesting the limbic system as the focus of dementia syndrome. Destruction of the limbic system in particular amygdala and hippampus produced the functional obstruction brought about by the marked reduction in the glucose utilization with PET in the bilateral temporal, parietal and occipital association cortices. Although this type constitutes only about 1/5 of all dementia patients. It is considered the fundamental type of dementia syndrome. Aside from this, there is a type wherein simultaneous and symmetrical reductions in glucose uterization of the frontal association cortex and the motor association cortex in the anterior part of the neocortex. This is referred to as type II. It constitutes about 4/5 of all dementia patients which is far more than type I. Based on these results, it is thought that limbic system is the main forcus of dementia syndrome.

Alzheimer's disease and multi-infarct dementia are the two main diseases entirely different from each other producing almost the same abnormalities as dementia syndrome. With magnetic resonance imaging, severe atrophy of amygdala and hippocampus in both Alzheimer's disease and multi-infarct dementia was observed. There was no essential difference on the atrophic findings between Alzheimer's disease and multi-infarct dementia. This result therefore suggest that the quantitative measurement of amygdaloid and hippocampal atrophy predicts dementia.

To make clear the characteristics of cerebral glucose uterization in dementia, PET studies with 18F-FDG were carried out. Taking the pattern of 18F-FDG uterization, dementia can be subdivided into two types. One type shows a simultaneous and symmetrical reduction glucose uterization in the posterior part of neocortex covering the temporal, parietal and occipital association cortices. This is referred to as type I. Although this type constitutes only about 1/5 of all dementia patients, it is considered the fundamental type of dementia. Aside from this, there is type wherein a simultaneous and symmetrical reduction in glucose uterization of the neocortex. This is type II. It constitutes about 4/5 of all dementia patients which is far more type I. There are no essential difference in the characteristics of cerebral glucose uterization in AD and MID. However, with regards the mean, AD is lower than MID. Various organic defect in neocortex do not correlate with the global reduction in glucose uterization in dementia patients. These results suggest that the reduction in glucose uterization in dementia may be functional disorder.