An atrioventricular dissociation characterized by independent and equally beating atrial and ventricular pacemakers, in the absence of a retrograde conduction. This case report describes new left bundle branch block and disappearance of the P wave in a patient undergoing transcatheter aortic valve. Junctional rhythms may show isorhythmic AV dissociation as the P waves and QRS complexes appear to have a close relationship to one.

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A year-old diabetic, hypertensive woman with prior stenting of her dominant right coronary artery underwent coronary arteriography because of an abnormal stress test. She went to the recovery room in good condition, and an electrocardiogram was recorded Figure. Electrocardiogram recorded after the coronary angioplasty.

See text for explication of the arrhythmia. In addition, nonspecific ST-T changes are present. At first glance no P waves are visible, but careful inspection of the lead II rhythm strip shows a notch on the downslope of all R waves except the fourth one from the beginning of the tracing and the fourth one from the end.

The perturbations of the QRS complexes are due to their occurring simultaneously with sinus P waves.

Thus, there is isorhythmic dissociation of an accelerated junctional rhythm from sinus rhythm. As is usually the case, the junctional rhythm is perfectly regular or nearly so, and slight sinus arrhythmia is dissociattion for the P waves being seen at the beginning or at the end of the QRSs.


In most cases, the P waves emerge more distinctly from the front or the back of the QRSs, i. Atrioventricular dissociation simply signifies that the atria dissociayion the ventricles have independent rhythms, either all of the time, i.

The electrocardiographer must state what rhythms are dissociated and why 1isornythmic. Although complete atrioventricular block is the quintessence of atrioventricular dissociation, it may occur with other arrhythmias Table 2. In many of these the sinus or atrial rhythm is too slow, and a junctional or ventricular escape rhythm has emerged.

Alternatively, an accelerated or frankly tachycardic junctional or ventricular rhythm has usurped control of the ventricles, but the atria maintain their own rhythm.

In this patient’s electrocardiogram the isorhhthmic P waves and the junction-initiated QRSs occur virtually simultaneously, and each occurs in the absolute refractory period of the other so that there are no atrial or ventricular captures. The mechanism of this coordination is unknown. If it is transient, it is termed accrochage; if it persists, it is called synchronization 1.

An electrocardiogram recorded 5 hours before this dissociahion also showed isorhythmic atrioventricular dissociation, but it was incomplete with occasional capture of the ventricles by the sinus-initiated impulses.

AV Dissociation Masquerading as an Accelerated Junctional Rhythm with Retrograde Atrial Activation

The following day there was sinus rhythm with marked sinus arrhythmia and P waves indicating left atrial enlargement. Otherwise the electrocardiogram resembled the one in the figure.


Accelerated junctional rhythm, the underlying mechanism of this patient’s atrioventricular dissociation, usually occurs in patients with structural heart disease, as was the case in our patient with diabetes mellitus, systemic arterial hypertension, and coronary arterial disease. The rhythm was present before the procedure as well as afterwards, so the cardiac catheterization and coronary angioplasty with stenting appear to have played no pathogenic role.

Isorhythmic atrioventricular dissociation in Labrador Retrievers.

National Center for Biotechnology InformationU. Proc Bayl Univ Med Cent. SubramaniamMD, James M. ParkerMD, and Sai K. Author information Copyright and License information Disclaimer. Open in a separate window. Some degree of antegrade and retrograde atrioventricular block often is necessary to prevent ventricular or atrial captures.

Accelerated junctional rhythm, isorhythmic atrioventricular dissociation, and hidden P waves

Some degree of retrograde atrioventricular block is necessary to prevent atrial captures, and at slower junctional or ventricular rates some degree of antegrade atrioventricular block is necessary to prevent ventricular captures and fusions. Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice: Theory and Practice in Health and Disease.

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