A fundamental study on monitoring cardiac functions of human beings in aerospace environment: computer diagnosis of electrocardiogram.
Explore the source record for details and available documents.
Computers↗
Biomedical subjects
J Toyama
Publications and source records attributed to J Toyama.
Serial MRI findings of benign poliomyelitis.
A 14-year-old boy presented with incomplete transverse myelopathic symptoms associated with mild encephalitis. Magnetic resonance imaging (MRI) revealed involvement of the central portion of spinal cord extending from the C1 to T5 level on T2-weighted images with expansion of the cervical spinal cord. The boy made a full clinical recovery in a few weeks. Cultures of the pharyngeal exudate were positive for ECHO virus type 11. The lesion on MRI disappeared completely in a few months.
Adolescent↗
Effects of cilazapril on ventricular arrhythmia in patients with congestive heart failure.
Angiotensin-converting enzyme (ACE) inhibitors reduce mortality and morbidity in patients with congestive heart failure. These effects may be mediated, at least in part, by suppression of lethal ventricular tachycardia (VT). The aims of this study were to examine whether the ACE inhibitor cilazapril reduces ventricular arrhythmia in patients with congestive heart failure and, if cilazapril does reduce ventricular arrhythmia, to determine whether this reduction is associated with suppression of sympathetic nerve activity in these patients. Thirty-two congestive heart failure patients (left ventricular ejection fraction, 35 +/- 6%; New York Heart Association class II or III) with VTs (Lown grade IVa or IVb) were randomly assigned to receive either conventional therapy, consisting of diuretics and digitalis (control group), or conventional therapy plus cilazapril (cilazapril group). Twenty-four-hour ambulatory electrocardiographic monitoring was performed at baseline and after 2 months of therapy. Plasma norepinephrine levels and heart rate variability (standard deviation about the mean RR interval) were compared at baseline and after 2 months of treatment. The control group demonstrated no significant change in arrhythmia frequency after 2 months of treatment. In the cilazapril group, however, the number of ventricular couplets and VT runs was significantly decreased. In association with this reduction, plasma norepinephrine levels were decreased, and heart rate variability was increased. These results suggest that cilazapril has antiarrhythmic effects, which may be produced by suppressing high sympathetic activity, in patients with congestive heart failure. It should be noted that the study group was small and that, although ventricular dysrhythmia was reduced with therapy, it remained substantial. Further study is needed to verify these results and to determine the exact causes of the reduction.
Aged↗
Electrical and mechanical effects of anthopleurin-A, a polypeptide from a sea anemone, on isolated rabbit ventricular muscle under conditions of hypoxia and glucose-free medium.
The effects of anthopleurin-A (AP-A, 1 x 10(-8) M) on the membrane action potential and contraction of isolated rabbit ventricular muscle were compared with those of ouabain (5 x 10(-7) M). Under control conditions, AP-A and ouabain showed submaximal (about 80% of maximal) positive inotropic effects without any toxic manifestations. AP-A caused a marked prolongation of action potential duration (APD) without affecting any other parameters of the action potential, whereas ouabain caused a shortening of APD and a slight decrease in maximum diastolic potential (MDP), overshoot (OS), and upstroke velocity (dV/dtmax) of the action potential. The positive inotropic effect of AP-A was relatively well maintained even under hypoxia or in glucose-free medium. Under these abnormal experimental conditions, AP-A caused a prolongation of APD only at the late stage of repolarization (APD80), whereas APD at the early stage of repolarization (APD30) was further shortened. Other parameters of action potential and resting tension (RT) were not influenced by AP-A. In contrast, under similar experimental conditions, ouabain caused no apparent positive inotropic action, but resulted in a marked increase in RT (contracture). In addition, after exposure to ouabain, a progressive shortening of APD and marked decreases in MDP, OS, and dV/dtmax were observed. These results indicate the AP-A has pharmacological properties quite different from those of ouabain and suggest possible advantages of this newly developed cardiotonic agent over cardiac glycosides when acting on the energy-depleted myocardium.
Animals↗
A protective effect of coenzyme Q10 on isolated rabbit ventricular muscle under hypoxic condition.
Effects of coenzyme Q10 (CoQ10) on transmembrane action potential, isometric tension, and tissue ATP contents of isolated rabbit ventricular muscles were examined under the hypoxic condition and subsequent reoxygenation. CoQ10 (10 mg/kg/day) was administered intravenously to 15 rabbits for 3 days (CoQ10 group), and 15 other rabbits were treated only with a vehicle for CoQ10 (control group). Membrane action potentials, mechanical contraction, and ATP contents of the preparations under aerobic condition were not affected by the CoQ10 or vehicle pretreatment. Hypoxia for 60 min caused a shortening of action potential duration (APD), a decrease in peak developed tension (DT), and an elevation of resting tension (RT), as well as a decrease in ATP contents of the preparations in both groups. However, these changes were significantly less in the CoQ10 group than those in the control group. A better recovery of APD, DT, and RT of the preparations during reoxygenation period was also observed in the CoQ10 group. These results indicate that the prior and repetitive administration of CoQ10 may protect cardiac muscles from functional deterioration induced by hypoxia, suggesting a beneficial effect of this substance on the metabolism of the energy-depleted myocardium.
Action Potentials↗
Electrophysiological effects of nipradilol (K-351) on isolated rabbit hearts and guinea pig ventricular muscles.
Effects of nipradilol (K-351), a newly developed antihypertensive agent, on electrophysiological properties of the heart were examined in Langendorff-perfused rabbit hearts and in superfused guinea pig ventricular muscles. In rabbit hearts, nipradilol at concentrations greater than 10(-5) M caused a significant prolongation of atrio-His bundle conduction time (AH) as well as His bundle-ventricular conduction time (HV), whereas heart rate (HR), functional refractory period of atrioventricular node (FRPVM) were unaffected. The intensity of the negative dromotropic effect of nipradilol was less than half that of propranolol. Isoproterenol-induced increase in HR and a shortening of AH, FRPAV, ERPVM were inhibited competitively by pretreatment with nipradilol at greater than 10(-8) M. Nipradilol was about two to three times more potent than propranolol in antagonizing isoproterenol-induced effects. In guinea pig ventricular muscles, nipradilol at a concentration greater than 10(-5) M caused a decrease of the maximum upstroke velocity (VMAX) of the action potential without affecting resting potential and action potential duration. In the presence of nipradilol, trains of stimuli at rates higher than 0.2 Hz led to an exponential decline in VMAX to achieve a new plateau. The time constant for the recovery from use-dependent block was 4.3 s. These findings suggest that nipradilol may have a potent cardiac beta-adrenoceptor blocking action and, at extremely high concentrations, quinidine-like inhibitory effects on the cardiac excitability and conductivity.
Action Potentials↗
Atrioventricular conduction in atrial fibrillation.
Explore the source record for details and available documents.
Acetylcholine↗
Electrophysiological effects of 711389-S, a new antiarrhythmic agent, on guinea-pig isolated cardiac muscle.
The effects of 711389-S, a newly developed antiarrhythmic agent, on transmembrane action potentials were examined in isolated papillary muscles of guinea pigs. 711389-S above 10(-6) M caused a dose-dependent decrease in the maximum upstroke velocity (Vmax) and a slight prolongation of the action potential duration (APD) at a late repolarization phase. The resting potential, the amplitude, and APD at an early repolarization phase were not affected even at 10(-5) M. In the presence of 711389-S, trains of stimuli higher than 0.1 Hz led to an exponential decline in Vmax to a new plateau level. This use-dependent block was augmented at the higher stimulation frequency. The time constant for the recovery from the use-dependent block was 47 s at 3 X 10(-6) M. At 1.0 Hz, 711389-S caused an appreciable shift (6.8 mV) of the curve relating the membrane potential and Vmax along the voltage axis in the hyperpolarizing direction, but no shift at 0.1 Hz. The antagonistic effect of 711389-S against acetylcholine in guinea-pig isolated atria was much less than that of disopyramide. These findings suggest that 711389-S has similar electrophysiological effects to those of other Class Ia antiarrhythmic drugs but has much less anticholinergic activity.
Acetylcholine↗