Onset of Retrograde Conduction

Report:

Top:

Sinus tachycardia 104/min

VEB

Monomorphic ventricular tachycardia 152/min

Retrograde conduction

Bottom:

Sinus tachycardia 110/min

Fusion VEBs in bigeminy

Monomorphic ventricular tachycardia 150/min

Retrograde conduction

Comment:

In both instances, VT starts with a late-diastolic beat – the first one on top of a sinus P wave, the second one immediately after sinus P wave. In both runs, 1:1 retrograde conduction to the atria develops one or two cycles after the onset, suppressing sinus activity and the possibility of sinus captures (even partial captures, the fusion or Dressler12, beats).

The runs recurred and lasted between 15 and 90 seconds, qualifying as both sustained (> 30”) and non-sustained (< 30”) VT. One spontaneous termination, just as Xylocaine was about to be given, is shown below (Fig 25a). A junctional escape beat precedes the resumption of sinus tachycardia.

Good general rule is not to treat recurrent episodes of tachycardia separately, either by boluses of drugs or (even less desirably) DC countershocks. There may be a role for antiarrhythmia pacing in some circumstances. Addressing the physiologic milieu and setting an infusion is the treatment of choice in most.

This patient later developed episodes of bigeminal tachycardia (Fig 25b), successfully treated by amiodarone.

25a. A spontaneous VT termination, followed by a junctional escape beat and sinus rhythm.

25b. An episode of bigeminal VT – bidirectional in some leads (best seen inV1) – at a later date. 26. 52 year old woman with palpitations. There is no clinical or echocardiographic heart disease.