Transient LBBB with RAD & Prolonged Interpolation Effect

Report:

Sinus rhythm and arrhythmia

VEBs, interpolated

Sustained PR interval prolongation

Left bundle branch block

Transient right axis deviation post-VEBs

Possible old anterolateral infarction

Comment:

Two things are of interest here: diminuendo PR intervals after interpolated VEBs and increase in QRS duration – still in LBBB conduction – with RAD in the beat following the VEB. The latter is presumably due to short cycle after the interpolated VEB – a rate-dependent aberrancy. This is most unusual.

The notched QRS complex in V6 and 1 may indicate an old infarction.

The patient had a permanent 1o AV block at other times (Fig 78a); this may explain the marked, prolonged effect of interpolation on his PR intervals.

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