Search PubMed⌕ Search

Biomedical subjects

T Musha

Publications and source records attributed to T Musha.

At least 73 records · Page 4Linked to original sources
PubMed1986

3-dimensional computer simulation of depolarization and repolarization processes in the myocardium.

A computer algorithm for 3-dimensional computer simulation of electric phenomena in the human heart has been completed, in which the heart model consists of 50,000 functional cells arranged in the cubic close-packed structure and various waveforms of the action potential have been allotted to these functional cells. The present model allows one to estimate time courses of ECG, VCG, and body surface potential distribution from the P-wave up to the T-wave. It also can simulate electric phenomena in the heart with anomalies in the conduction system and the myocardium.

Action Potentials↗
PubMed1985

Dipolarity and dipole location during QRS and T waves in normal men estimated from body surface potential distribution.

The dipolarity of the body surface potential distribution and the locus of the main dipole were estimated mathematically at 2 msec intervals in 27 normal men. The nondipolar content showed time-dependent fluctuation during the QRS. It increased sharply at early and later phases of the QRS. The main dipole moved smoothly within the actual cardiac region and was inscribed in a clockwise direction in most cases. The nondipolar content during the ST-T period was smaller and with less fluctuation than that during the QRS. The main dipole during the T wave moved less than 2 cm near the center of the heart. These results indicated that although a fairly large percentage of the body surface potential could be represented by a single moving dipole, the nondipolar content was larger during initial and late phases of the QRS. It was also suggested that the ventricular repolarization process can be better approximated by a single fixed dipole in normal men.

Adult↗
PubMed1984

Estimation of the rising phase of EPSP analyzed by computer simulation of the coding process.

Based on data obtained from intracellular recordings of cat alpha-motoneurons in the stretch reflex, the firing process of these motoneurons was computer-simulated. The impulse response EPSP (IR-EPSP) was simulated to correspond to a monosynaptic mass EPSP elicited by a spindle afferent volley, while the returning potential was simulated to correspond to a potential gradient rising toward an augmenting depolarization of the membrane (augmentative EPSP) after motoneuronal spike generation. The IR-EPSPs were generated by input at random intervals and added to each other, linearly, on the returning potential. As soon as the resultant potential attained the critical threshold level, Vth, motoneuron firing occurred. Then IR-EPSPs were again added to the returning potential until another motoneuron firing occurred. This process was repeated continuously, and the time relation between input and output, lag-time distribution (PT(T], was determined Distribution of the bias potential, PV(V), from which the motoneuron spike triggering EPSP started to rise, was also calculated. The relations between PT(T), PV(V) and a waveform of the IR-EPSP were obtained analytically. The relation indicated that the shape of PT(T) corresponds to a time derivative of the rising phase of the IR-EPSP if the PV(V) distribution is uniform. In this study, we investigated the possibility of making the PV(V) distribution uniform.

Animals↗
PubMed1982

Moving multiple dipole model for cardiac activity.

A single-dipole model and a two-dipole model have been examined to approximate the electrical activity of heart; positions as well as vector components of these dipoles were estimated from the body surface potential distribution that was measured with 64 electrodes arranged on the chest. The "residue" has been defined as a measure for how much potential component is left that cannot be attributed to the equivalent dipoles. A locus of the vector end of an equivalent dipole in the single-dipole model is very much like ordinary vectorcardiogram (VCG). The residue has a peak in the last half of QRS; this means that the single-dipole approximation is not valid there. Then another dipole is introduced, which is the two-dipole approximation. The residue has been greatly reduced and the peak disappears; the resultant two dipoles move around in the right and left parts of the heart with nearly opposite directions. The moving-two-dipole model for normal subjects describes the cardiac activity in QRS much better than with the moving-single-dipole model.

Electrocardiography↗