The effect of hypoxia on experimental ventricular tachycardia

Jacobson, Eugene D.; Schiess, William A.; Moe, Gordon K.

doi:10.1016/0002-8703(62)90152-7

Cited by 11 publications

(4 citation statements)

References 13 publications

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“…The results described here indicate that in the dog with a ligated coronary artery glucagon is effective in attenuating ventricular ectopic activity, which is an arrhythmia aetiologically similar to that accompanying acute myocardial infarction in man (Clark & Cummings, 1956;Jacobson, et al, 1962). These findings, when considered together with the observations of other workers, widen the spectrum of potentially useful activity of glucagon in acute myocardial infarction.…”

Section: Discussionsupporting

confidence: 69%

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Effect of glucagon on ventricular arrhythmias after coronary artery occlusion and on ventricular automaticity in the dog

MADAN

1971

British J Pharmacology

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Summary In anaesthetized dogs, glucagon (100 μg/kg i.v.), caused a significant increase in heart rate and decrease in mean arterial blood pressure. Ventricular automaticity, as determined by the time to the onset of first vagal escape beat and the number of such indioventricular beats during the 30 s period of vagal stimulation, was not significantly altered. In unanaesthetized dogs with ventricular arrhythmias produced by two‐stage ligation of the anterior descending branch of the left coronary artery, glucagon (30 and 100 μg/kg i.v.), restored normal sinus rhythm in a few animals. In the remaining dogs, there was a significant reduction in the ventricular ectopic activity. The significant positive chronotropic response to glucagon elicited in anaesthetized animals was not observed in conscious dogs whose coronary arteries had been ligated. These findings enhance the potential usefulness of glucagon in the treatment of acute myocardial infarction, which may often be associated with disturbances of ventricular rhythm. In the light of observations made by other workers, it is suggested that the antiarrhythmic effect of glucagon may be due to movement of potassium ions into the cardiac cell.

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Section: Discussionsupporting

confidence: 69%

“…This indicates the relative stability of the arrhythmia in the dogs with ligated coronary arteries, which has also been observed previously (Harris. 1950;Jacobson, Schiess & Moe, 1962).…”

Section: Effects Of Ligationmentioning

confidence: 99%

Effect of glucagon on ventricular arrhythmias after coronary artery occlusion and on ventricular automaticity in the dog

MADAN

1971

British J Pharmacology

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“…The phase of delayed ventricular arrhvthmias has not occupied as much attention with respect to this particular issue. One study (26) showed that systemic hypoxia mitigated the ectopic ventricular activity of the later phase.…”

Section: Discussionmentioning

confidence: 99%

Electrophysiological Properties of Canine Purkinje Cells in One-Day-Old Myocardial Infarction

Lazzara

El‐Sherif

Scherlag

1973

Circulation Research

244

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Electrophysiological mechanisms which underlie the ectopic ventricular beats occurring 1 day after occlusion of the anterior descending coronary artery of dogs were explored. In intact dogs, bipolar electrograms were recorded in the infarcted and normal zones. Both Purkinje and ordinary myocardial potentials were recorded from the endocardial surface of the normal zone, but only Purkinje potentials were recorded from the infarcted zone. The Purkinje potentials in the infarcted zone were diminished in amplitude and rapidity. The threshold for endocardial pacing was higher in the infarcted zone than it was in the normal zone. The refractory periods of Purkinje cells were longer in the infarcted zone than they were in the normal zone. Excised specimens of endocardial surface containing the infarcted zone were superfused with Tyrode's solution. No ordinary myocardial cells were electrically active at the endocardial surface of the infarcted zone. Purkinje cells showed diminished resting and action potentials, reduced upstroke velocity, enhanced automaticity and phase 4 depolarization, and long action potentials with prolonged phase 3. Excitability was depressed within the infarcted zone. During superfusion, even with Tyrode's solution poor in oxygen and free of dextrose, Purkinje cells recovered toward normal with respect to amplitude of resting and action potentials, upstroke velocity, automaticity, and excitability. The prolonged action potentials persisted. Repetitive firing was easily elicited within the infarcted zone. Various types of pacemaker activity were detected within the infarcted zone. Thus Purkinje cells in the infarcted zone showed distinctive alterations in electrophysiological properties which were probably related to deleterious factors that accumulated in that zone. It is likely that the arrhythmia which occurred in the intact dogs at this time originated within the altered Purkinje cells of the infarcted zone. KEY WORDSprolonged action potentials enhanced automaticity recovery hypoxia working myocardium pacemaker reentry

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“…It also appears unlikely that hypoxia plays an important role as an arrhythmogenic factor in the 24-hour infarcted dog heart. Previous studies have shown that hypoxia reduces rather than enhances the automatic firing rate of infarcted tissue (35,36).…”

Section: Factors Responsible For Early and Late Ventricular Arrhythmiasmentioning

confidence: 93%

Characterization and Localization of Ventricular Arrhythmias Resulting from Myocardial Ischemia and Infarction

Scherlag

El‐Sherif

Hope

et al. 1974

Circulation Research

369

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Electrocardiograms and electrograms were recorded in 18 dogs anesthetized with sodium pentobarbital. Using endocardial and epicardial plunge wire electrodes in normal and ischemic or infarcted areas, activation of Purkinje and regular muscle tissue was studied within the first 20-30 minutes and 24 hours after anterior descending coronary artery ligation. The ventricular arrhythmias in the first 20 minutes were abolished during vagally induced atrial arrest, but ventricular automaticity was unchanged from that during the control period. These rate-related arrhythmias were uniformly associated with marked diminution and delay of epicardial activation in the ischemic zone. Slowing of the heart rate caused recovery of the timing, form, and duration of these epicardial potentials with the coincident disappearance of ventricular arrhythmias. The ventricular arrhythmias of the early phase spontaneously subsided with time 20-30 minutes after ligation; concurrently, epicardial activation in the ischemic zone improved. The ventricular arrhythmias noted 24 hours after coronary artery ligation were revealed by vagally induced atrial slowing and suppressed by rapid atrial pacing, indicating the existence of enhanced ventricular automaticity. There was a loss of endocardial muscle activation; Purkinje tissue was depressed but viable in the infarcted zone. The sequence of firing during many of the multifocal ventricular ectopic beats showed that the earliest activation arose from Purkinje tissue in the infarcted zone. However, other ectopic beats appeared to arise from infarcted epicardial muscle. KEY WORDS ventricular automaticity ventricular electrograms atrial pacing anesthetized dogs Purkinje fibers reentry vagal stimulation• Harris and Rojas in 1943 (1) described two distinct phases of ventricular arrhythmias after major coronary artery ligation in the dog. Sudden one-stage occlusion of the left anterior descending coronary artery close to its origin in the dog results in a high incidence of rapid paroxysmal ventricular tachycardia which usually degenerates into ventricular fibrillation within the first 20 minutes (1). If the dog survives the early arrhythmic episodes, a relatively quiescent period ensues followed by another prolonged interval of rapid ventricular ectopic activity. This later arrhythmic period starts MethodsEighteen adult mongrel dogs were anesthetized with sodium pentobarbital (30 mg/kg, iv). Under controlled ventilation, the thorax was opened at the fourth intercostal space, and the heart was exposed via a pericardiotomy. The left atrial appendage was reflected, and the left anterior descending coronary artery was exposed within 1 or 2 cm of its origin. Silk ligatures were then placed 3 7 2

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The effect of hypoxia on experimental ventricular tachycardia

Cited by 11 publications

References 13 publications

Effect of glucagon on ventricular arrhythmias after coronary artery occlusion and on ventricular automaticity in the dog

Effect of glucagon on ventricular arrhythmias after coronary artery occlusion and on ventricular automaticity in the dog

Electrophysiological Properties of Canine Purkinje Cells in One-Day-Old Myocardial Infarction

Characterization and Localization of Ventricular Arrhythmias Resulting from Myocardial Ischemia and Infarction

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