VEBs: Trigeminy & Trigeminy

Report:

Sinus arrhythmia

Left atrial abnormality (LAA)

First degree AV block

Atrial ectopic beat (second P wave in the bottom strip)

VEBs in trigeminy

Concealed retrograde conduction

Comment:

In the top strip, every third P wave is blocked by a VEB. In the bottom strip, at a slower rate and a longer R-P interval, all the P waves are conducted, although with longer PR intervals after the VEBs. The trigeminy changes from two sinus cycles followed by a VEB (top strip) to interpolated VEBs in alternate cycles. The upper strip’s VEBs have completely compensatory pauses; the interpolated ones cause no pauses at all.

The atrial ectopic beat is the third one in the bottom strip. The sinus escape cycle that follows it is longer than others, presumably from post-ectopic sinoatrial depression. The sinus rate itself is irregular, with sinus arrhythmia and a tendency to long-short cycle length alternation.

Below (Fig 140a) is a similar pair of strips, from a 67 year old woman on Day 4 of a large inferolateral MI complicated by VF. In both, every third P wave is blocked; completely so in the upper strip, producing trigeminy. In the lower strip, the block is only latent (1o), producing an allorhythmia. The sinus beats that follow the VEBs in the lower strip show an early RBBB aberrancy.