AVNRT differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Supraventricular tachycardias must be differentiated from each other because the management strategies may vary:

Atrial Fibrillation

• Rate: 110 to 180 bpm
• Rhythm: Irregularly irregular
• P waves: Absent, fibrillatory waves
• PR interval: Absent
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology in the absence of abberant conduction
• Response to Maneuvers: Does not break with adenosine or vagal maneuvers
• Epidemiology and Demographics: More common in the elderly, following bypass surgery, in mitral valve disease, hyperthyroidism

Atrial Flutter

• Rate: 75 (4:1 block), 100 (3:1 block) and 150 (2:1 block) bpm, but 150 is most common
• Rhythm: Regular
• P waves: Sawtooth pattern of P waves at 250 to 350 beats per minute
• PR interval: Varies depending upon the magnitude of the block, but is short
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
• Response to Maneuvers: Conduction may vary in response to drugs and maneuvers dropping the rate from 150 to 100 or to 75 bpm
• Epidemiology and Demographics: More common in the elderly, after alcohol

AV Nodal Reentry Tachycardia

• Rate: In adults the range is 140-250 bpm, but in children the rate can exceed 250 bpm.
• Rhythm: Regular
• P waves: The p wave is usually superimposed on or buried within the QRS complex
• PR interval: The PR interval cannot be calculated as the p wave is generally obscured by the QRS complex. In uncommon AVNRT, the p wave can appear after the QRS complex and before the T wave, and in atypical AVNRT, the p wave can appear just before the QRS complex.
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology in the absence of abberant conduction, QRS alternans may be present
• Response to Maneuvers: May break with adenosine or vagal maneuvers
• Epidemiology and Demographics: Accounts for 60%-70% of all SVTs. 80% to 90% of cases are due to antegrade conduction down a slow pathway and retrograde up a fast pathway.

AV Reciprocating Tachycardia

• Rate: More rapid than AVNRT
• Rhythm:
• P waves:
• PR interval:
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
• Response to Maneuvers: May break with adenosine or vagal maneuvers
• Epidemiology and Demographics: More common in males, whereas AVNRT is more common in females, Occurs at a younger age

Junctional Tachycardia

• Rate: > 60 beats per minute
• Rhythm: Regular
• P waves: Usually inverted, may be burried in the QRS complex
• PR interval: The p wave is usually buried in the QRS complex
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
• Response to Maneuvers: Does not break with adenosine or vagal maneuvers
• Epidemiology and Demographics: Common after heart surgery, digoxin toxicity, as an escape rhythm in AV block

Multifocal Atrial Tachycardia

• Rate: Atrial rate is > 100 beats per minute (bpm)
• Rhythm:
• P waves: P waves of varying morphology from at least three different foci, absence of one dominant atrial pacemaker, can be mistaken for atrial fibrillation if the P waves are of low amplitude
• PR interval: Variable PR intervals, RR intervals, and PP intervals
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
• Response to Maneuvers: Does not terminate with adenosine or vagal maneuvers
• Epidemiology and Demographics: * High incidence in the elderly and in those with COPD

Sinus Node Reentry Tachycardia

• Rate:
• Rhythm:
• P waves: Upright P waves precede each regular, narrow QRS complex
• PR interval:
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
• Response to Maneuvers: Although it cannot be distinguished on the surface 12 lead EKG from sinus tachycardia, SA node reentry tachycardia does often terminate with vagal maneuvers unlike sinus tachycardia.
• Epidemiology and Demographics:

Sinus tachycardia

• Rate: Greater than 100.
• Rhythm: Regular.
• P waves: Upright, consistent, and normal in morphology (if no atrial disease)
• PR interval: Between 0.12–0.20 seconds and shortens with increasing heart rate
• QRS complex: Less than 0.12 seconds, consistent, and normal in morphology
• Response to Maneuvers:
• Epidemiology and Demographics:

Ventricular Tachycardia

• Rate:
• Rhythm: Generally regular
• P waves: Normal morphology, upright, but dissociated from the QRS complex (i.e. "march through" the QRS complex)
• PR interval:
• QRS complex: Wide and greater than 0.12 seconds
• Response to Maneuvers: Does not terminate in response to adenosine or vagal maneuvers
• Epidemiology and Demographics:
• Risk Factors:: Occurs in the context of myocardial ischemia, myocardial infarction, congestive heart failure, drug toxicity, and inhereted channelopathies

Wolff-Parkinson-White syndrome

• Pathophysiology: Anatomically and functionally, the fast and slow pathways of AVNRT should not be confused with the accessory pathways that give rise to Wolff-Parkinson-White syndrome (WPW) syndrome or atrioventricular re-entrant tachycardia (AVRT). In AVNRT, the fast and slow pathways are located within the right atrium in close proximity to or within the AV node and exhibit electrophysiologic properties similar to AV nodal tissue. Accessory pathways that give rise to WPW syndrome and AVRT are located in the atrioventricular valvular rings, they provide a direct connection between the atria and ventricles, and have electrophysiologic properties similar to ventricular myocardium.
• Rate:
• Rhythm:
• P waves: In WPW with orthodromic conduction due to a bypass tract, the p wave generally follows the QRS complex, whereas in AVNRT, the p wave is generally buried in the QRS complex.
• PR interval:
• QRS complex: In WPW there is a delta wave and evidence of ventricular preexcitation if there is conduction to the ventrilce via antegrade conduction down an accessory pathway. It should be noted, however, that in some patients with WPW, a delta wave and pre-excitation may not be present because bypass tracts do not conduct antegrade.
• Response to Maneuvers: May break in response to procainamide, adenosine, vagal maneuvers
• Epidemiology and Demographics:
• Risk Factors: None, an inhereted disorder

References

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