Accelerated junctional rhythm, isorhythmic atrioventricular dissociation, and hidden P waves.
Subject: Arrhythmia (Risk factors)
Arrhythmia (Diagnosis)
Arrhythmia (Care and treatment)
Circadian rhythms (Health aspects)
Electrocardiogram (Usage)
Electrocardiogram (Health aspects)
Electrocardiography (Usage)
Electrocardiography (Health aspects)
Authors: Glancy, D. Luke
Subramaniam, Pramilla N.
Parker, James M.
Devarapalli, Sai K.
Pub Date: 10/01/2009
Publication: Name: Baylor University Medical Center Proceedings Publisher: The Baylor University Medical Center Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 The Baylor University Medical Center ISSN: 0899-8280
Issue: Date: Oct, 2009 Source Volume: 22 Source Issue: 4
Geographic: Geographic Scope: United States Geographic Code: 1USA United States
Accession Number: 209406709
Full Text: [FIGURE OMITTED]

A 62-year-old diabetic, hypertensive woman with prior stenting of her dominant right coronary artery underwent coronary arteriography because of an abnormal stress test. A 90% narrowing of the left circumflex coronary artery beyond the second obtuse marginal branch was stented with a 3 x 18-mm drug-eluting stmt. She went to the recovery room in good condition, and an electrocardiogram was recorded (Figure).

The QRS complexes are narrow and occur regularly at a rate of 98 beats/min. 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. Each of those QRSs has a notch at the beginning of the upslope of the R wave that corresponds to a small upward deflection at the beginning of the QRS in the simultaneously recorded lead V1, whereas all other V1 QRSs are pure QS complexes. 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 responsible 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.e., Ps and QRSs are less synchronized, than is seen here.

Atrioventricular dissociation simply signifies that the atria and the ventricles have independent rhythms, either all of the time, i.e., complete dissociation, or intermittently, i.e., dissociation is incomplete due to atrial and/or ventricular captures. The electrocardiographer must state what rhythms are dissociated and why (1, 2). 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 sinus-initiated 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 one also showed isorhythmic atrioventricular dissociation, but it was incomplete with occasional capture of the ventricles by the sinus-initiated impulses. 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.

(1.) Surawicz B, Knilans TK. Chows Electrocardiography in Clinical Practice: Adult and Pediatric, 5th ed. Philadelphia: WB Saunders, 2001:367-388.

(2.) Bar FW, den Dulk K, Wellens HJJ. Atrioventricular dissociation. In Macfarlane PW, Lawrie TDU, eds. Comprehensive Electrocardiology: Theory and Practice in Health and Disease. New York: Pergamon, 1989:933-959.

D. Luke Glancy, MD, Pramilla N. Subramaniam, MD, James M. Parker, MD, and Sai K. Devarapalli, MD

From the Sections of Cardiology, Departments of Medicine, Louisiana State University Health Sciences Center and the Medical Center of Louisiana, New Orleans. Corresponding author: D. Luke Glancy, MD, 7300 Lakeshore Drive, #30, New Orleans, Louisiana 70124 (e-mail: dglano@lsuhso.edu). sit
Table. Some causes of complete
atrioventricular dissociation *

* Sinus or atrial rhythm with complete antegrade and retrograde
  atrioventricular block and a junctional or ventricular escape rhythm.

* Sinus or atrial bradycardia with a junctional or ventricular escape
  rhythm.
  Some degree of antegrade and retrograde atrioventricular block often
  is necessary to prevent ventricular or atrial captures.

* Junctional or ventricular accelerated rhythm or tachycardia. 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.

* Synchronization of the sinus or atrial pacemaker with the junctional
  or ventricular pacemaker so that each discharges in the absolute
  refractory period of the other and thus cannot capture it.

* Modified from reference 2.
Gale Copyright: Copyright 2009 Gale, Cengage Learning. All rights reserved.