Escape-Capture Bigeminy in AF

Report:

Atrial fibrillation 1

High-grade or complete AV block 1

Junctional rhythm 2

Pacemaker rhythm 1

Escape-capture bigeminy 1

Left anterior hemiblock (LAHB) 1

Right bundle branch block 1

Anteroseptal infarction, age uncertain 1

ST/T changes consistent with ischæmia 1

Comment:

The f waves are visible in the anteroseptal leads. The analogous RR intervals are identical, making it unlikely that the RBBB complexes are transmitted AF. It is true that VEBs or paced beats can ‘regularise’ the response to AF, but, in the absence of advanced or complete AV block, the intervals should show some variation.

An alternative diagnosis here would be pacemaker rhythm with junctional extrasystoles in bigeminy. This too would account for the fixed coupling. Junctional extrasystoles in bigeminy are uncommon, or at least less common than junctional rhythm. The relevant points may be claimed for either diagnosis.

Below (Fig 21a), there are no native complexes and the heart is paced regularly at 70/min. The tracing is shown for its spuriously narrow QS or rS morphology in V1, due to an initial isoelectric segment of the paced beats. It tended that way in the original trace of Fig 21 above.