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Biomedical subjects

J Toyama

Publications and source records attributed to J Toyama.

At least 37 records · Page 2Linked to original sources
PubMed1978

Computational reconstruction of body surfact isopotential maps in myocardial infarction: comparison between nontransmural and transmural infarction.

The relationship between the lack of electromotive force in myocardial infarction and body surface potential distribution was investigated on maps reconstructed from a simulated heart model and transfer impedance vectors of human torso model. The heart model, a cluster of 3-mm cubic blocks, was stored in the memory of a computer. Transfer impedance vectors between 81 lead points on the human torso model and 392 positions covering ventricular areas in the torso were measure. Body surface potential values were calculated mathematically by summing up scalar products between the electromotive force of the heart model and the measured transfer impedance vectors. Thus, reconstructed maps changed in their patterns with the alternation in lacation and/or extent of infarcted region in the heart model. In particular, the appearance of the abnormal potential minimum, which projects the infarcted region in the heart model onto the torso surface, was characteristic in both transmural and subendocardial infarction. In addition, delayed activation in the intact layer of the epicardium overlying the infarcted region produced a potential maximum on the same place as the abnormal potential minimum appeared previously.

Action Potentials↗
PubMed1978

Body surface isopotential maps. Clinical application to the diagnosis of myocardial infarction.

This paper is a review of recent work relating body surface isopotential maps to the detection of the site and extent of myocardial infarction in cases which are either indetectable or difficult to diagnose through the use of standard 12 lead ECGs. According to the difference of the site and extent of myocardial infarction, the characteristic maps are obtained. Through the use of body surface isopotential maps, the significant clinical information may be obtained in a number of cases, and we can do better with mapping than without it in the evaluation of patients with myocardial infarction.

Adult↗
PubMed1978

Effects of beta-adrenergic blocking drug pindolol (LB46) on cardiac fibers in relation to its membrane effects.

Direct membrane effects and beta-adrenergic blocking action of pindolol were studied comparatively on isolated perfused cardiac fibers of dogs. In Purkinje fibers, the duration of transmembrane action potential decreased in concentrations higher than 0.5 mg/L. Maximum rate of depolarization also decreased in higher concentrations (5.0 mg/L or more). The functional refractory period decreased to a lesser degree compared with the decrease of the action potential duration. Nevertheless, slow-rising action potentials could not be abolished in premature responses, probably because of membrane depressant effects of this drug. In ventricular muscle fibers, these changes were minimum in the same range of concentrations. On the other hand, 0.05 mg/L of pindolol which was close to the therapeutic plasma concentrations and had no effect on action potentials of both Purkinje and ventricular muscle fibers, minimized the increase in automaticity of Purkinje fibers induced by 0.2 mg/L of isoproterenol. It is rationally speculated that the mechanism of antiarrhthmic action of pindolol is mainly due to its beta-adrenergic blocking action.

Action Potentials↗
PubMed1978

Effects of l-penbutolol (Hoe 893d) on the transmembrane potentials of canine purkinje fibers and ventricular muscle fibers.

Intrinsic membrane effects (non-specific effects) and beta-adrenergic blocking action (specific effects) of l-penbutolol were studied using intracellular microelectrode techniques. l-Penbutolol in concentrations above 0.1 mg/L reduced the maximum rate of depolarization at phase O of both Purkinje fibers and ventricular muscle fibers without affecting their maximum diastolic potential. The action potential duration of Purkinje fibers were also shortened. The shortening of action potential duration and enhancement of automaticity in Purkinje fibers, normally induced by isoproterenol (0.2 mg/L), were antagonized by l-penbutolol in much lower concentraions (0.1--1.0 microgram/L) than those at which nonspecific effects are observed. The difference between these two concentration ranges is sufficient to suggest that l-penbutolol might be a highly specific beta-adrenergic blocking agent.

Action Potentials↗
PubMed1977

Diagnosis of right ventricular infarction: experimental study through the use of body surface isopotential maps.

This investigation was designed to diagnose right ventricular infarction, which is difficult to diagnose by the standard twelve-lead ECG, through the use of body surface isopotential maps which have significant diagnostic information. Right ventricular infarction was experimentally caused by ligation of the canine right coronary artery. Each dog had a series of maps recorded before and a week after experimentally-induced myocardial infarction. The common features of maps in right ventricular infarction are: 1. In the early stage of the ventricular depolarization the negative area occupies a comparatively large part of the right anterior chest surface, and in the middle stage, the larger part of the right anterior surface is also occupied by the negative area. 2. A minimum appears on the right anterior chest surface in the early stage. The delayed excitation resulting from intraventricular conduction disturbance caused by infarction, as verified by the epicardial isochronic map, is also well represented by the body surface isopotential map. In conclusion, through the use of body surface isopotential maps, it is much easier to diagnose right ventricular infarction and intraventricular conduction disturbance caused by infarction even in cases in which the standard twelve-lead ECG does not show the abnormalities clearly.

Animals↗
PubMed1977

Experimental study of myocardial infarction through the use of body surface isopotential maps: ligation of the anterior descending branch of the left coronary artery.

This investigation was undertaken to diagnose the location and extent of myocardial infarction with the use of maps which give significant information about the ventricular activation process. Myocardial infarction was experimentally caused by ligation of the anterior descending branch of the left coronary artery. All classes were classified into three groups (A,B, and C) according to the location and extent of infarction. The map of each group had its own characteristics, as follows. In Group A no pisitive potentials appeared on the left anterior chest surface all through ventricular depolarization. In Group B, like Group A, the negative area occupied the whole left anterior chest surface in the early stage. But in the later stages there appeared a positive area on the left anterior surface. As to Group C, there was no abnormality in its early stage, but in its middle stage, the negative area was found on the left anterior chest surface. Thus the sequential maps can be helpful in diagnosing the location and extent of myocardial infarction, and will be applied to clinical use much more.

Animals↗
PubMed1977

Diagnosis of high posterior infarction: experimental study through the use of body surface isopotential maps.

This investigation was designed to diagnose high posterior infarction easily through the use of body surface isopotential maps. High posterior infarction was experimentally caused by ligation of the branch of the circumflex artery of the canine left coronary artery. Each dog had a series of maps recorded before and four weeks after experimentally induced myocardial infarction. The common features of maps in high posterior infarction are: 1) The positive area expanded into the dorsal surface so slowly that, in the middle stage of the ventricular depolarization, a large area of the dorsal surface was still covered by the negative area. 2) from the middle to the late stage, the absolute value of the minimum significantly decreased and absolute potential of the dorsal surface also significantly decreased. In conclusion, we propose that it is possibile to diagnose high posterior infarction through the use of maps.

Animals↗
PubMed1977

Gastric sarcoidosis in Japan.

Seventeen cases of gastric sarcoidosis have been reported in Japanese literature. Age distribution was from the 3rd decade (6 cases) to the 6th decade (3 cases) and the sex ratio was 2 females to 1 male. Preoperative diagnosis included 10 cases of gastric carcinoma and 6 cases of gastric ulcer. Sites of the granulomas were limited to the mucous membrane in 4 cases, from serosa to the mucous membrane in 9 cases and from the muscle layer to the mucous membrane in 1 case. As there are granulomas in the mucous membrane in all cases, it appears that granulomas may spread from the mucous membrane to outside and they can possibly be detected by biopsy. There were no BHL in any chest X-ray. Kveim test was positive in only 2 out of 11 cases. Prognosis is very good. There has been a question whether the gastric granuloma is a local or a generalized manifestation. From our findings, we will report in detail, it may not be a local reaction, but a gastric manifestation of generalized sarcoidosis.

Adult↗