- Author: Chirag M Sandesara, MD; Chief Editor: Jeffrey N Rottman, MD more...
Atrioventricular (AV) dissociation is a condition in which the atria and ventricles do not activate in a synchronous fashion but beat independently of each other. AV dissociation usually refers to the situation in which the ventricular rate is the same or faster than the atrial rate.[1, 2] When the atrial rate is faster and the atria and ventricles are beating independently, complete heart block is present; this is distinct from AV dissociation. While complete heart block can be properly considered a form of AV dissociation, it is discussed in detail in Atrioventricular Block and is not considered further in this article. Also, in AV dissociation, no retrograde ventriculoatrial conduction occurs.
When the atrial rate is the same as the ventricular rate but the P wave is not conducting, the rhythm disturbance is known as isorhythmic AV dissociation. When the rates are similar but occasionally the atria conduct to the ventricles, the rhythm is known as interference AV dissociation.
AV dissociation can be a benign phenomenon and can be complete or incomplete. When incomplete, some of the P waves conduct and capture the ventricles (ie, interference AV dissociation), but if they do not, it is complete AV dissociation. Complete AV dissociation can mimic AV block, but the fact that none of the P waves conduct has more to do with timing of the P waves in relation to the QRS complex rather than the presence of AV block.
A normal cardiac impulse arises from the sinus node and is conducted through the AV junction, the bundle of His, and the bundle branches to the ventricles. The sinus node is the dominant pacemaker because its intrinsic rate is faster than subsidiary pacemakers in the AV junction or in the ventricle. AV dissociation can result from (1) slowing of the dominant pacemaker (sinus node), which allows an escape junctional or ventricular rhythm, or (2) acceleration of a normally slower (subsidiary) pacemaker, such as a junctional site or a ventricular site that activates the ventricles without retrograde atrial capture.
Conditions that can initiate AV dissociation include surgical and anesthesia interventions (including intubation), conditions that increase catecholamine levels (including infusions of inotropes) and drugs that block catecholamines, sinus node disease, digoxin toxicity, myocardial infarction and other structural heart disease, hyperkalemia, vagal activation (eg, neurocardiogenic syncope, vomiting), ventricular tachycardia, or ventricular pacing. AV dissociation can be seen after radiofrequency ablation of the slow pathway responsible for AV nodal reentry if some of the vagal fibers are damaged. After exertion, if AV dissociation is present from an escape pacer, it can be a normal phenomenon. Whatever the cause, AV dissociation usually is secondary to some other cause.
Little epidemiologic information is available regarding the frequency of AV dissociation.
The prognosis of AV dissociation depends on the underlying cardiac condition and effects of drug toxicities.
AV dissociation by itself can be benign. Any adverse effects are related to ensuing bradycardia, AV dyssynchrony, or underlying conditions.
Braunwald E. Atrioventricular dissociation. Braunwald E, Zipes DP, Libby P, eds. Heart Diseases: A Textbook Of Cardiovascular Medicine. 6th ed. WB Saunders Co: Philadelphia, Pa; 2001.
Wagner GS. Atrioventricular dissociation. Wagner GSS, Marriott HJ, eds. Marriott's Practical Electrocardiography. Baltimore, Md: Williams & Wilkins; 1994. 9th ed:
Oreto G, Smeets JL, Rodriguez LM, et al. Wide complex tachycardia with atrioventricular dissociation and QRS morphology identical to that of sinus rhythm: a manifestation of bundle branch reentry. Heart. 1996 Dec. 76(6):541-7. [Medline].
Ho RT, Pietrasik G, Greenspon AJ. A narrow complex tachycardia with intermittent atrioventricular dissociation: What is the mechanism?. Heart Rhythm. 2014 Nov. 11(11):2116-9. [Medline].
Duffield JS, Jacob AJ, Miller HC. Recurrent, life-threatening atrioventricular dissociation associated with toxoplasma myocarditis. Heart. 1996 Nov. 76(5):453-4. [Medline].
Luzza F, Oreto G. Pseudo-atrioventricular dissociation caused by interpolated ventricular extrasystoles in the presence of dual atrioventricular nodal pathway. Chest. 1994 May. 105(5):1587-9. [Medline].
Ogunlade O, Akintomide AO, Ajayi OE, Eluwole OA. Marked first degree atrioventricular block: an extremely prolonged PR interval associated with atrioventricular dissociation in a young Nigerian man with pseudo-pacemaker syndrome: a case report. BMC Res Notes. 2014 Nov 4. 7:781. [Medline]. [Full Text].
Pick A. A-V dissociation. A proposal for a comprehensive classification and consistent terminology. Am Heart J. 1963 Aug. 66:147-50. [Medline].