Change of Cardiac Rhythm in the Rabbit after an Atrial Premature Beat

Bonke, F. I. M.; Bouman, L. N.; Rijn, Henny E. Van

doi:10.1161/01.res.24.4.533

Cited by 85 publications

(22 citation statements)

References 14 publications

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“…12). This suggests that there is considerable slowing of conduction in this region, confirming previous reports (Sano and Yamagishi, 1965;Bonke et al, 1969). It is important to note that earlier premature beats undergo much greater slowing of conduction (Figs.…”

Section: Discussionsupporting

confidence: 90%

Characterization of refractoriness in the sinus node of the rabbit.

Kerr¹,

Prystowsky²,

Browning³

et al. 1980

Circulation Research

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SUMMARY Recovery cycles following premature atrial stimulation introduced during atrial pacing may fall into four categories: reset, incomplete interpolation, complete interpolation, and echo responses. It has been postulated that the transition from reset to incomplete interpolation may represent the point at which premature beats can no longer enter the sinus node and reset it and thus reflect the refractory period of the sinus node. The purpose of this study was to explore the electrophysiological basis underlying the transition from reset to incomplete interpolation and. to assess the spatial orientation of refractoriness in the sinus node. In 15 rabbit sinus node preparations, premature atrial stimuli were introduced at varying degrees of prematurity while intracellular potentials were recorded with a microelectrode in the sinus node. In 12 of 15 experiments, transition from reset to incomplete interpolation immediately followed a sudden reduction in action potential amplitude, rendering the action potential incapable of resetting the node. This point was interpreted as the effective refractory period of the sinus node. During the zone of incomplete interpolation, low voltage depolarizations were seen in the node, interfering with diastolic depolarization and delaying the recovery beat. These small depolarizations were absent during the zone of complete interpolation. In six experiments, the microelectrode was moved toward the crista terminalis in steps of 50 to 100 /im, and the stimulation sequence at each site was repeated. By examining relative action potential amplitude at various sites at the same premature interval, it was possible for us to construct curves showing the pattern of block of premature impulses. We found that progressively earlier premature beats are blocked at progressively greater distances from the node. Therefore, tissue between the crista terminalis and the sinus node provides a progressive gradation of refractoriness, rather than a discrete barrier. Circ Res 47: 742-756, 1980

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Section: Discussionsupporting

confidence: 90%

Characterization of refractoriness in the sinus node of the rabbit.

Kerr¹,

Prystowsky²,

Browning³

et al. 1980

Circulation Research

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“…When the premature beat is elicited at the end of the cycle, causing a curtailed cycle (CC, the interval between the last spontaneous discharge and the premature beat) that is only 10% or less shorter than the normal interval (NP), the postextrasystolic pause is compensatory, i.e., so much longer than the normal interval as the curtailed cycle is shorter (CC + PEP = 2 NP). When the premature beat is elicited earlier in the cycle, the postextrasystolic pause is longer than the normal interval but not long enough to be compensatory (12 Upon shortening the curtailed cycle, the duration of the postextrasystolic pause increases. When a premature beat is elicited very early in the atrial cycle, the postextrasystolic pause has a shorter duration than the normal interval.…”

Section: Effect Of An Atrial Premature Beatmentioning

confidence: 97%

“…If the premature discharge of fiber C was a driven one, then the impulse had to come at last from the vicinity of fiber A with a latency more than five times longer than during spontaneous action. Even the fact that premature beats are conducted more slowly than normal beats, cannot account for such a tremendous change in latency (12). Therefore, it is more likely that a group of fibers including fiber C was discharging spontaneously, thereby taking over the function of pacemaker.…”

Section: Effect Of An Atrial Premature Beat Elicited By a Stimulus 79mentioning

confidence: 99%

Effect of an Early Atrial Premature Beat on Activity of the Sinoatrial Node and Atrial Rhythm in the Rabbit

Bonke

Bouman

Schopman

1971

Circulation Research

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In the spontaneously beating isolated right atrium of the rabbit, premature beats were elicited by electrical stimulation. When the premature beat was elicited early in the atrial cycle, the postextrasystolic pause had a short duration and the sum of the pre-and postextrasystolic pause was about the same as the duration of a normal spontaneous interval. We have tried to demonstrate, using simultaneous multiple microelectrode impalements of SA node fibers, that by such an early atrial premature beat the atrium could be activated by a reentrant mechanism. The results of our experiments led us to the conclusion that the impulse of the premature beat, elicited early in the atrial cycle, discharges the SA node only fractionally and that the fibers in the neighborhood of the activated area are influenced electrotonically. This causes a change of both the site and the moment of the spontaneous impulse formation. The SA node discharges spontaneously after such an early premature beat. Reentry activation is likely to occur when a series of atrial premature beats is observed. A supraventricular tachycardia might be caused by repeated atrial discharges following a stimulus very shortly after the atrial refractory period. KEY WORDSpostextrasystolic arrhythmia reentry activation atrial tachycardia intranodal conduction electrotonus in heart muscle SA node entrance block pacemaker shift interaction of nodal fibers• During their detailed investigations into disturbances of rhythm produced by atrial premature beats, Eccles and Hoff (1,2) found that a premature beat elicited early in the atrial cycle was followed by a subsequent beat which occurred earlier than expected. The premature beat cycle and the subsequent cycle together had about the same duration as one normal spontaneous cycle. However, they and others who had observed this phenomenon (3, 4) were not able to offer a satisfactory explanation. In recent literature (5-7), an atrial activation shortly after an atrial premature beat is called an echo, or reentrant, activation. These studies, however, are con-

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“…We interpret our findings as indirect expression of a sinoatrial pacemaker shift which hitherto has been validated in animal experiments only.9 10 Furthermore, such observations serve to contribute to the present debate about measuring sinoatrial conduction time in man.…”

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confidence: 51%

Sinoatrial pacemaker shift following atrial stimulation in man.

Steinbeck¹,

Lüderitz²

1977

Circulation

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Indirect evidence of a sinoatrial pacemaker shift after programmed atrial stimulation in man is presented. Following electrically induced beats, time intervals and postextrasystolic morphology of atrial electrogram and P waves were scrutinized in 30 catheterization studies. Applying premature atrial stimulation, a decrease of the interval between the last basic atrial depolarization and the stimulus-produced atrial excitation (curtailed cycle) below a critical interval was followed by a sinoatrial pacemaker shift in three cases. This electrophysiologic event consisted of a concomitant change in shape of high right atrial electrogram and an increase of atrial cycle length. Simultaneous alteration of P waves could be detected in 2/3 patients. Assuming that the pacemaker shift indicates the arrival of ectopic activation in the sinus node, capture of the sinus node by the premature beat could be distinguished from failure to capture. Thus, pacemaker shift can be used for estimating sinoatrial conduction time in addition to present methods using measurement of postextrasystolic atrial intervals. The changes described could be seen both before and after atropine administration. Tracings of a pacemaker shift after cessation of rapid atrial pacing are also presented. In summary, we found a sinoatrial pacemaker shift underlying sinus node response to ectopic atrial activation in man, a phenomenon which contributes to our understanding of indirect assessment of sinoatrial conduction time by the premature stimulation technique.

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Change of Cardiac Rhythm in the Rabbit after an Atrial Premature Beat

Cited by 85 publications

References 14 publications

Characterization of refractoriness in the sinus node of the rabbit.

Characterization of refractoriness in the sinus node of the rabbit.

Effect of an Early Atrial Premature Beat on Activity of the Sinoatrial Node and Atrial Rhythm in the Rabbit

Sinoatrial pacemaker shift following atrial stimulation in man.

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