Right Ventricular Outflow Tract Tachycardia

Report:

Ventricular tachycardia 155/min

Possible A-V dissociation

Comment:

The tachycardia complexes are just under 0.12” in duration and have, in a way, left bundle branch block morphology with marked (+100o) right axis deviation. There appear to be dissociated P waves in V1. This could be called fascicular VT, but in this case more is actually known about its precise origin from the electrophysiologic studies (EPS) in Sydney. All the paroxysms arose from the right ventricular outflow tract. Most had a retrograde Wenckebach conduction – some of this may well be what is seen in V1 as “dissociated” P waves. This foreknowledge may have biased the above report. Recently, a pulmonary artery variety of this tachycardia has been described, with larger R waves in the inferior leads and larger aVL/aVR Q wave ratio19. This trace would fit it nicely, but the V1 and V2 morphology spoils it (and rightly so, in view of its known origin in the RVOT): a larger R/S ratio should be seen there.

The sinus rhythm ECGs were always normal, even on sotalol therapy. The one below (Fig 14a) has a couplet of VEBs obviously from the same focus as the VT. There is no retrograde conduction: the blocked sinus P wave can be easily seen between the VEBs, both of which are squeezed in the same compensatory pause.

14a. A pair of VEBs, otherwise normal trace. 15. 53 year old woman ventilated in ICU for presumed pulmonary vasculitis.