Diagnostic Considerations
It is important to determine if atrioventricular (AV) conduction is intact, particularly in patients with an accelerated junctional rhythm following cardiac surgery—this may indicate significant AV conduction disease.
Proper review of the patient's medication list is essential in determining the cause as well. High digoxin levels can be associated with AV dissociation. It is equally as important to treat other medical causes that may have led to AV dissociation, such as correction of potassium levels (if too high or low) or urgent treatment of renal failure for the same reasons.
If isorhythmic AV dissociation is difficult to differentiate from sinus rhythm, increasing the sinus rate with a position change or walking may help make the diagnosis.
Important considerations in the differential diagnosis
It is important to differentiate AV dissociation from AV block and from blocked premature atrial complexes. Blocked premature atrial contractions may appear to resemble AV dissociation but in AV block and in AV dissociation the atrial rate is constant (except if AV dissociation is due to ventricular tachycardia and there is intermittent retrograde conduction).
Conditions to consider in the differential diagnosis of AV dissociation are ventricular tachycardia and any supraventricular tachycardia that includes nonparoxysmal or paroxysmal junctional tachycardia with complete or intermittent retrograde block. [15, 16, 17]
Bundle branch reentry ventricular tachycardia is associated with AV dissociation, as the reentrant circuit usually requires antegrade conduction via the right bundle branch and retrograde conduction via the left bundle branch. The atria are not part of the reentry circuit.
AV dissociation is rare in supraventricular tachycardias. AV nodal reentry tachycardia or even orthodromic tachycardia associated with a nodofasicular or nodoventricular bypass tract may demonstrate AV dissociation. If AV dissociation occurs, it is transient because the atria may not necessarily be part of the reentry circuit.
Differential Diagnoses
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Blocked Premature Atrial Complexes
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Bundle Branch Reentry Ventricular Tachycardia
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Nonparoxysmal or Paroxysmal Junctional Tachycardia with Complete or Intermittent Retrograde Block
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Orthodromic Tachycardia
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Atrioventricular Dissociation. Significant slowing of the sinus node allows for a subsidiary pacemaker (atrioventricular [AV] junction) to activate, causing AV dissociation.
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Atrioventricular Dissociation. This rhythm strip reveals interference atrioventricular dissociation, as there is a P wave conducting to the ventricle in the third and seventh beats, whereas the P wave fails to conduct to the ventricle in the other beats.
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Atrioventricular Dissociation. Isorhythmic AV dissociation. There is AV dissociation with independent atrial and ventricular conduction at similar rates.
