![]() (The second junctional impulse conducts to the atria because the atria have not been occupied by the sinus impulse and are available). ![]() Situations that may result in AV dissociation are listed in Table 1 and examples of some of these are shown in Figure 1.ĪV dissociation with: (A) Junctional premature beat. Interference dissociation may occur with a junctional escape beat, a ventricular extrasystole, or a series of beats as in accelerated junctional or ventricular rhythm or ventricular tachycardia. However, it is possible for the rate of subsidiary pacemakers to approach that of the sinus by either slowing of the sinus rate, a pause in the sinus rhythm, speeding of the subsidiary pacemaker, or a combination of these. Normally, the sinus rate is faster than the rate of subsidiary pacemakers consequently, their pacemaker capability is not given a chance to manifest. ![]() This situation is sometimes called “interference dissociation” because two pacemakers are interfering with the propagation of each other's impulse, whereas the AV dissociation from CHB has been called “block dissociation” (a rarely used term).ĭissociation in these circumstances is an obligatory or inevitable response in that, faced with either a physiologic refractory period or AV block, the P wave and the QRS from another source have no other way to behave but to dissociate. In this regard, the physiologic refractory period of cardiac tissues comprise both absolute as well as relative components, both of which impact transmission of the cardiac impulse, and may establish a basis for AV dissociation.ĭuring sinus rhythm (or, rarely, atrial rhythm) if a QRS complex triggered from another source (AV junction or ventricle) occurs close in time to the P wave, such that the P wave and the QRS fall during the physiologic refractory period of each other (or that of the AV node), the impulse from the atrium cannot conduct to the ventricle and the impulse from the ectopic source cannot conduct to the atrium AV dissociation results. The latter may happen in junctional or ventricular arrhythmias including escape or accelerated rhythm, tachycardia, or premature beats.Ĭonclusion: The crucial clinical point is not the AV dissociation itself, but that an underlying triggering primary disorder is present and should be identified.Īnn Noninvasive Electrocardiol 2011 16(3):227–231Ĭardiac tissue, after depolarization, must repolarize before it can respond to subsequent stimuli (i.e., the tissue is said to be refractory). Results: AV dissociation is often an obligatory, secondary phenomenon, and should not be construed as the primary disorder it may be due to either the AV conduction system being completely blocked (3° AV block) or the P wave and the QRS complex being generated from separate sources (usually, the AV junction or ventricle) but occurring close together during the physiologic refractory period of each other. Methods: This article examines the basis and clinical implications of AV dissociation. The clinical significance of AV dissociation is often misunderstood. Background: The independent activation of the atria and ventricles, AV dissociation, is a common phenomenon that occurs during a wide variety of electrophysiologic circumstances. ![]()
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