Les Phénomènes de Synchronisation au Niveau du Cœur

Segers, M

doi:10.3109/13813454609144874

Cited by 39 publications

(18 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The more symmetrical relation in this experiment resulted in a stable 1:1 entrainment zone that extended from periods that were briefer to periods that were longer than the intrinsic pacemaker cycle length. Discussion Cardiac pacemakers can be entrained by external periodicities in their environment (Segers, 1946;Levy et al, 1969;Moe, 1979b, Jalife et al, 1980a). In the steady state, the period of the entrained pacemaker can become identical to that of the entraining periodicity.…”

Section: Prc Symmetry Determines the Lower Limit Of Entrainmentmentioning

confidence: 99%

Dynamic vagal control of pacemaker activity in the mammalian sinoatrial node.

Jalife¹,

Slenter²,

Salata³

et al. 1983

Circulation Research

View full text Add to dashboard Cite

SUMMARY. Dynamic heart rate control by parasympathetic nervous input involves feedback mechanisms and reflex bursting of efferent cardiac vagal fibers. Periodic vagal bursting induces phasic changes in sinoatrial cycle length and can entrain the pacemaker to beat at periods that may be identical to those of the vagal burst. We investigated the electrophysiological basis of these phenomena in isolated sinus node preparations (rabbit, cat, and sheep). In the presence of propranolol (3.9 X 10~6 M), relatively brief (50-150 msec) trains of stimuli, applied onto the endocardial surface of the preparation, activated postganglionic vagal terminals and induced a brief hyperpolarization of sinoatrial pacemaker cells. This vagally mediated hyperpolarization could alter the pacemaker rhythm by an amount that depended on its duration and its position in the cycle, as well as on the duration of the free-running pacemaker period. When the free-running period was sufficiently long and the hyperpolarization was induced sufficiently early in the spontaneous cycle, a "paradoxical" acceleration of the pacemaker rhythm ensued. Phasic changes were plotted on phase-response curves, constructed by scanning systematically the sinoatrial pacemaker period with single or repetitive vagal trains. These phase-response curves enabled us to predict the entrainment characteristics and the levels of synchronization of the pacemaker to the vagal periodicity. The overall data explain the cellular mechanisms involved in the phasic effects of brief vagal discharges on sinoatrial periodicity, and provide conclusive evidence for the prediction that repetitive vagal input is capable of forcing the cardiac pacemaker to beat at rates that can be faster or slower than the intrinsic pacemaker rate. These data should improve our knowledge of the dynamic control of heart rate by neural reflexes and aid in our understanding of rhythm disturbances generated by the interaction of the cardiac pacemaker with vagal activity. (Circ Res 52: 642-656, 1983)

show abstract

Section: Prc Symmetry Determines the Lower Limit Of Entrainmentmentioning

confidence: 99%

Dynamic vagal control of pacemaker activity in the mammalian sinoatrial node.

Jalife¹,

Slenter²,

Salata³

et al. 1983

Circulation Research

View full text Add to dashboard Cite

show abstract

“…The mechanism responsible for the synchronization of atria and ventricles has not been investigated extensively. The principal explanations advanced involve electrical or mechanical coupling between the atria and ventricles (1). An electrical interaction between the atrial and ventricular pacemakers This work was supported by U. S. Public Health Service Grant HE-10951-03 from the National Heart Institute.…”

mentioning

confidence: 99%

Mechanism of Synchronization in Isorhythmic Dissociation

Levy

Zieske²

1970

Circulation Research

View full text Add to dashboard Cite

Third degree heart block was produced in anesthetized dogs by injecting 95% ethanol into the region of the A-V node. When the ventricles were paced artificially at a constant rate near the spontaneous rate of the S-A node, then the atria and ventricles became synchronized. During synchronization, the P wave oscillated rhythmically around the QRS. When the P preceded the QRS, the arterial blood pressure increased, whereas when the P wave followed the QRS, the blood pressure fell. Synchronization depended on such rhythmical fluctuations in blood pressure because (1) when the blood pressure changes were severely attenuated, synchronization ceased, and (2) simulation of the blood pressure changes by means of a servo-controlled pump also produced synchronization. A biological control system operates in such a way that (1) the P-R interval affects blood pressure by virtue of changes in the atrial contribution to ventricular filling; (2) the blood pressure has an inverse effect on atrial frequency through the baroreceptor reflex, and perhaps other mechanisms; and (3) changes in atrial frequency alter the P-R interval, to complete the control loop.

show abstract

“…When the 2 rates are similar, within a few percent difference, accrochage is quite common; at rates varying by more than 25%, it does not happen at all, at least in fragments of a frog heart, where it was first observed. 2 The actual mechanism remains unknown, but a likely explanation is that as the PR interval shortens, the ventricular output decreases and there is a reflex, baroreceptor-mediated acceleration of the sinus rate. 3 This is in keeping with known effects of variable atrioventricular delay on the ventricular stroke volume.…”

mentioning

confidence: 99%

Accrochage

Nikolić

2003

Heart & Lung

View full text Add to dashboard Cite

The patient was a 78-year-old woman 30 minutes after a hypoxic/hypercarbic arrest on the ward. The event was attributed to timolol eye drops. Her gas exchange normalized with bronchodilators and mechanical ventilation. The blood pressure was 136 over 86 mm Hg and remained stable; routine laboratory investigations were non-contributory.The monitor showed periods of variable PR interval, without any other observable changes.The sinus P waves encroached on the succeeding QRS complex but never merged with it or emerged on the other side. The above sequence recurred several times over the next 2 hours.The middle strip starts with what looks like sinus rhythm, except that the PR intervals are clearly shorter than in the top strip. The rhythm is now an

show abstract

Les Phénomènes de Synchronisation au Niveau du Cœur

Cited by 39 publications

References 11 publications

Dynamic vagal control of pacemaker activity in the mammalian sinoatrial node.

Dynamic vagal control of pacemaker activity in the mammalian sinoatrial node.

Mechanism of Synchronization in Isorhythmic Dissociation

Accrochage

Contact Info

Product

Resources

About