Left Atrial Abnormality

Report:

Sinus rhythm

Left atrial abnormality

First degree AV block

PR 0.36”

Normal axis

Left bundle branch block

QRS 0.125”

Comment:

The P waves are 0.12” (3 mm) long. Their P-terminal force (PTF) in lead V1 is well over 1 mm deep and 1 mm long. Finally, they are notched, with inter-peak distance of over 1 mm.

The notching is the feature students remember most, like with RBBB. However, in neither case is the notching essential or even important criterion. Significant notching, however, should involve a trough at least 0.04” (1 mm) long. This may be due to a lesion in the interatrial tract – Bachmann’s bundle.

The correct thing to report is left atrial abnormality . This is because the above findings may represent an intra-atrial conduction defect alone, or dilatation, or true hypertrophy; rarely, right atrial enlargement. P mitrale is now abandoned, for pedantic and misplaced reasons, but officially abandoned it is. Not by me, though: old Cardiologists should serve as a bridge to the past.

The LBBB, although relatively narrow (perhaps just evolved from the incomplete LBBB), shows typical monophasic R complexes in the left ventricular leads and a QS in V1. Like this one, 50% of LBBBs have normal frontal plane axis; some like calling those “predivisional”. It seems to sound more impressive in some parts of the world.