A narrow QRS tachycardia

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Diagnosis
Supraventricular Arrythmias, Atrioventricular nodal reentrant tachycardia
2 to 1, Slow-Fast, Atypical AVNRT, Unconclusive PPI, Anterograde jump, Slow-pathway ablation

We performed an anterograde EP study. An atypical tachycardia is induced. Diagnostic manoeuvers are provided.

History of the patient

57 y.o. women with an history of palpitation. No 12 leads recording available. She experienced 3 to 4 crisis of 1h to 9h each year. There is no structural heart disease. She came for an electrophysiological study.

Comments

This is a "slow-fast" AVNRT. 

Anterograde EP study showed us an anterograde jump on a slow pathway. The first induced tachycardia conducts in 2 to 1 to the ventricle with a CS concentric activation, thus excluding an AVRT. After re-induction in 1 to 1, the VA is prolonged (> 60 ms) and rules out a typical "fast-slow" AVNRT. 

A first PPI do not capture the atria and is unconclusive. A second PPI is much more convincing with a late A capture during V pacing, a long Stimulation to A conduction, a pseudo-VAAV response. A pseudo-VAAV response eliminate a atrial tachycardia. A "slow-fast" AVNRT is the only diagnosis remaining.

During ablation a slow junctionnal rhythm is expected with a 1 to 1 with a short VA ratio. Facing a missing retrograde P wave, we stopped ablation after 45 secondes. PR remained normal. 

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