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Biomedical subjects

R Ruffy

Publications and source records attributed to R Ruffy.

45 records · Page 3Linked to original sources
PubMed1979

Electrophysiological effects of ethmozin on canine myocardium.

The electrophysiological effects of ethmozin on canine myocardium were studied in anesthetised open-chest animals and in superfused Purkinje fibres. The drug did not change spontaneous sinus node cycle length and atrioventricular conduction time when selectively injected into the sinus nodal artery and into the posterior septal artery, respectively. Right and left ventricular diastolic excitability threshold and refractory period were increased following the intravenous administration of ethmozin, 4 mg/kg-1. Ethmozin (3 to 5 mg/kg-1 i.v.) markedly increased conduction delay in the ischaemic zone of the left ventricle during acute coronary artery occlusion. This change was associated with the development of ventricular fibrillation in 50% of the dogs. In vitro, ethmozin 1 X 10(-3) and 1 X 10(-2) g.litre-1 shortened Purkinje fibres' action potential duration. At 1 X 10(-2) g.litre-1, ethmozin decreased the rate of rise of phase 0, and slightly reduced action potential amplitude.

Action Potentials↗
PubMed1979

Relationship between changes in left ventricular bipolar electrograms and regional myocardial blood flow during acute coronary artery occlusion in the dog.

The purpose of this study was to determine whether a quantitative relationship existed between a reduction in regional myocardial blood flow, measured by radiolabeled microspheres, and the degree and type of changes in myocardial activation recorded in bipolar left ventricular subepicardial and subendocardial electrograms, in open-chest dogs following acute coronary artery occlusion. We found that the degree of regional myocardial ischemia was related quantitatively to the reduction in amplitude recorded with bipolar electrograms in the subepicardium and subendocardium, and to the increase in duration of subepicardial electrograms. Other characteristics measured in electrograms did not relate to the degree of ischemia. Despite a comparable reduction in regional myocardial blood flow, subepicardial conduction delay exceeded that recorded in the subendocardium, which often exhibited accelerated conduction.

Acute Disease↗
PubMed1979

[Electrophysiologic effect of ethmosine on the dog's myocardium].

The electrophysiologic effects of ethmozin on canine myocardium were studied in anesthetized open-chest animals and in superfused Purkinje fibers. On selective injection into the sinus node artery and the posterior septal artery the drug caused no changes in the sinus node length and atrioventricular conduction, respectively. Intravenous infusion of 4 mg/kg ethmozin led to an increase of right and left ventricular diastolic excitability threshold and refractory period. Intravenous administration of 3--5 mg/kg ethmozin caused marked increase in conduction delay in which the ischemic zone of the left ventricle during acute coronary artery occlusion, which was associated with ventricular fibrillation in 50% of the dogs. In vitro, 1 x 10(-6) g/ml ethmozin shortened the Purkinje fibers' action potential duration whereas a dose of 1 x 10(-5) g/ml reduced the rate of phase 0 rise and slightly reduced the action potential amplitude. Ethmozin in a dose of 1 x 10(-7) g/ml increased transiently the isometric developed tension of false-tendon preparations. Higher concentrations caused marked depression of contractility. These observations suggest depression of the fast current by ethmozin. However, further studies are needed to elucidate its effect on action potential duration and false-tendor contractility.

Action Potentials↗
PubMed1977

Exit block of artificial pacemaker induced by carotid sinus massage.

Failure of the pacemaker is a common complication of pacemaker therapy. Identification of the disorder responsible for the failure to pace is often difficult. An increase in myocardial threshold can result in nonconduction of the artificial impulse, particularly near the end of the life of the battery, when the output of current has started to decline. This report demonstrates such an increase in myocardial resistance which was apparent only upon massage of the carotid sinus.

Aged↗
PubMedDate not supplied

Influence of acute coronary artery occlusion on direct ventricular defibrillation in dogs.

Automatic defibrillators have been successfully tested in normal animals. However, human candidates for implantation of such devices are likely to have ischemic heart disease. This study examined the optimal site of defibrillation and the influence of acute myocardial ischemia upon the defibrillation threshold in anesthetized dogs. The defibrillation threshold was determined from a transvenous right ventricular intracavitary electrode and from right and left ventricular epicardial electrodes. Shocks were delivered before and after occlusion of the left anterior descending coronary artery. Before occlusion, the rate of successful shocks was low from the right ventricular epicardium, moderate from the right ventricular cavity, and high from the left ventricular epicardium. Furthermore, the defibrillation threshold was significantly lower at the left ventricular epicardium than at the right ventricular sites. During coronary artery occlusion, the rate of successful defibrillation remained high from the left ventricular epicardium, and there was no significant change in the defibrillation threshold. It was concluded that the left ventricular epicardium is the optimal site for defibrillation in the anesthetized dog. Acute coronary artery occlusion did not modify the success rate of defibrillation or the energy required for defibrillation.

Animals↗