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VA-nishing act

-when fusion fails & confusion prevails-

Patient presentation

  • 22 year old male

  • recurrent palpitations

  • documented tachycardia on ECG
    -    narrow complex, regular tachycardia
    -long RP
    -sudden offset

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Differential diagnosis

  • AVNRT (atypical)

  • AVRT

  • Junctional tachycardia

  • Atrial tachycardia

Baseline ECG

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Retrograde paced extras

  • MIdline (CS 9,10) non-decremental VA conduction

  • No retrograde jumps

  • VA ERP 380

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Parahisian pacing

  • Same VA interval during RV only pacing and non-selective HIS capture

  • consistent with pathway conduction

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Incremental atrial pacing

  • AV wenckebach 525ms

  • no evidence of pre-excitation

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Paced atrial extras

  • No AH jump

  • AVN ERP 460ms

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Sensed atrial doubles (on Isuprel)

  • Repeatable single echoes-
    --Long VA (atypical echo)
    -midline activation

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Tachycardia induction

  • Induced with sensed atrial doubles on high dose Isuprel

  • Narrow complex tachycardia with midline atrial activation (CS 9,10)

  • TCL 318ms

  • VA interval 168ms

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Tachycardia termination

  • Terminates with a V

  • Unlikely JT

  • Nothing else ruled out

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HIS synchronous VPB

  • Shows atrial advancement 
    -active pathway (AVRT) or
    -bystander pathway

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HIS synchronous VPB

  • Shows tachycardia with VA block 
    -active pathway (AVRT)
     

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Ventricular entrainment - 320ms

  • Unable to entrain the atrium without terminating tachycardia

  • Entrains the atrium on the 1st fully captured beat
    -    consistent with AVRT

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Diagnosis

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Earliest activation

  • Postero-septal RA

  • Lack of VA fusion noted - quite separated VA

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Post ablation

  • VA dissociation

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Reasons for lack of fusion of VA at pathway insertion site

​Slow conducting pathways (PJRT)

  • PJRT is a rare SVT (<1% of SVTs)

  • Rates vary between 120-250 bpm

  • Inverted p waves in II, III, aVF

  • PR interval shorter than RP interval

  • Usually near the ostium of the CS
     

  • May also have slow conduction if the pathway has been damaged (previously ablated with some recovery)

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Oblique pathways

  • Oblique accessory pathways although rare, result in different location of the earliest atrial and ventricular activation sites.

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References

  • Wang et al. (2015). An unusual atrioventricular accessory pathway with an oblique course. Heart rhythm case reports, 1(6), 411-415
     

  • Otomo, et al. (2001). Reversing the Direction of Paced Ventricular and Atrial Wavefronts Reveals an Oblique Course in Accessory AV Pathways and Improves Localization for Catheter Ablation. Circulation, 550-556
     

  • Parvin et al. (1999). Clinical Course of Persistent Junctional Reciprocating Tachycardia. Journal of the American College of Cardiology, 33 (2), 366-375
     

  • Dick (2010) Clinical cardiac electrophysiology in the young.

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