ECG of the week 105
ECG challenge by Dr. Mauro Toniolo, Division of Cardiology, University Hospital of S. Maria Della Misericordia, Udine, Italy.
What is the most likely arrhythmia based on these pictures?
C. Paroxysmal AF
Answer to this week"s challenge by Dr. Mauro Toniolo EHRA_ESC young committee member, Division of Cardiology, University Hospital of S. Maria Della Misericordia, Udine, Italy.
The first picture bellow shows the induction of a narrow QRS tachycardia with atrial programmed electrical stimulation: there is a quadripolar catheter localized in the coronary sinus (CS) and a quadripolar catheter localized in high right atrium (HRA). On the base of the first picture, no differentialdiagnosis can be done but there is a broad prolongation of the AV interval just before the induction of the tachicardia (transition from a fast pathway to a slow pathway).
The second picture shows the same narrow QRS tachycardia with a quadripolar catheter localized in His region farther. The tachycardia shows a long AH interval (anterograde slow pathway) and a very short HA interval (retrograde fast pathway). The most likely diagnosis is a slow-fast atrioventricular nodal reentrant tachicardia (AVNRT). Possible but less likely diagnosis are an atrial tachicardia (AT) with a very long AH interval (1° degree AV block) or an atrioventricular reciprocating tachycardia (AVRT) with a slow (AV It is very important to consider the different mechanisms of these arrythmias:
- AVNRT and AT are arrhythmias where the ventricle is not part of the circuit and so we must consider AH and HA intervals (ventricle could be also dissociated!)
- AVRT is an arrhythmia where the ventricle is part of the circuit and so we must consider AV and VA intervals (His is generally retrogradely by-passed from the circuit)
In the third picture there is the differential diagnosis between AVNRT and AVRT with a para-hisian pacing: where there is a ventricular capture (wide QRS) the VA interval is longer than where there is a hisian capture (narrower QRS): the retro conduction occurs between the His bundle and not between an accessory pathway. AT was ruled-out through an overdrive pacing from the ventricle in tachycardia (not shown). The final diagnosis is a AVNRT.
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