What is the difference in diagnosis and treatment between atrioventricular reentrant tachycardia (AVRT) and atrioventricular nodal reentrant tachycardia (AVNRT)?

AVRT vs AVNRT: Diagnosis and Treatment

Key Diagnostic Distinction

The critical ECG difference is P-wave timing: AVNRT shows P waves buried within or immediately at the end of the QRS complex (creating pseudo-R' in V1 or pseudo-S waves in inferior leads), while AVRT displays clearly visible retrograde P waves in the ST segment, separated from the QRS by >70 ms. 1, 2

Anatomic and Mechanistic Differences

AVNRT (Atrioventricular Nodal Reentrant Tachycardia)

• Circuit location: Confined entirely within the AV node and small amount of perinodal atrial tissue, using dual pathways ("fast" and "slow") within the node itself 2, 3
• Typical form: Anterograde conduction down the slow pathway, retrograde up the fast pathway 2
• Atrial activation: Nearly simultaneous with ventricular activation, causing P waves to be hidden 1, 2

AVRT (Atrioventricular Reentrant Tachycardia)

• Circuit location: Requires an accessory pathway (extranodal connection) connecting atrium to ventricle across the AV groove, plus the AV node, atrium, and ventricle 2, 4
• Orthodromic form: Impulse travels down the AV node (anterograde) and up the accessory pathway (retrograde) 2
• Atrial activation: Sequential after ventricular activation, producing visible P waves in early ST segment 1, 2

ECG Diagnostic Features

AVNRT Characteristics

• P waves: Absent or buried within QRS complex 1
• Pathognomonic signs: Pseudo-R' wave in V1 and/or pseudo-S waves in leads II, III, aVF 1, 2
• RP interval: Very short (P wave at end of QRS or invisible) 1
• Rate: Typically 180-200 bpm, range 110 to >250 bpm 1

AVRT Characteristics

• P waves: Clearly visible retrograde P waves in ST segment, separated from QRS by >70 ms 1
• P-wave morphology: Reflects accessory pathway location (e.g., deeply inverted in inferior leads with posteroseptal pathways) 2
• RP interval: Longer than AVNRT, with visible separation 1

Critical Pitfall

In atypical AVNRT variants with long RP intervals, the rhythm can mimic atrial tachycardia or AVRT—careful P-wave analysis is essential. 2

Clinical Presentation Patterns

AVNRT

• Demographics: More common in middle-aged/older patients with female predominance 1, 2
• Age of onset: Mean 32±18 years 2
• Characteristic symptom: "Neck pounding" or "shirt flapping" sensations due to atrial contraction against closed tricuspid valve 2

AVRT

• Demographics: More prevalent in adolescents and younger adults 2
• Age of onset: Mean 23±14 years 2
• Associated condition: May occur with Wolff-Parkinson-White syndrome (pre-excitation) 4

Acute Treatment

Both AVNRT and AVRT (Identical Initial Approach)

First-line therapy:

• Vagal maneuvers (Class I recommendation) 1, 2
• Adenosine IV (Class I recommendation) 1, 2, 3
  • Both respond by blocking AV nodal conduction 2

If vagal maneuvers and adenosine fail:

• IV beta-blockers, diltiazem, or verapamil (Class IIa) in hemodynamically stable patients 1

Hemodynamic instability:

• Synchronized cardioversion (Class I) 1

Critical Safety Warning for AVRT

Never administer verapamil or diltiazem to patients with AVRT and pre-excitation (Wolff-Parkinson-White) during atrial fibrillation—this can cause hemodynamic collapse or ventricular fibrillation. 2, 4 If diagnosis is uncertain and QRS is wide, treat as ventricular tachycardia 1.

Ongoing Management

AVNRT

Definitive treatment:

• Catheter ablation of slow pathway (Class I recommendation) 1
  • High success rate, low complications, becoming first-choice therapy 3

Medical management (for patients declining or not candidates for ablation):

• Oral verapamil or diltiazem (Class I) 1
• Oral beta-blockers (Class I) 1
• Flecainide or propafenone (Class IIa) in patients without structural/ischemic heart disease 1

AVRT

Definitive treatment:

• Catheter ablation of accessory pathway (Class I recommendation) 1, 2
  • Success rate 95-100% 2
  • Targets the accessory pathway itself, not the AV node 2

Medical management: Same options as AVNRT for patients declining ablation 1

Advanced Electrophysiologic Differentiation

When diagnosis remains uncertain during EP study:

• Differential ventricular entrainment: In AVNRT, corrected post-pacing interval minus tachycardia cycle length (cPPI-TCL) >30 ms or VA interval >20 ms when comparing RV base vs apex pacing (100% predictive) 5
• DeltaHA criterion: Positive values (HA during entrainment minus HA during SVT) indicate AVNRT; negative values indicate AVRT (100% sensitivity/specificity) 6
• Local VA index: >40 ms distinguishes AVNRT from AVRT with septal accessory pathways 7