Atrial Tachycardia with LBBB Aberrancy

Report:

Sinus rhythm

SVEB (first beat)

4-beat run of atrial tachycardia

Left bundle branch block aberrancy

Comment:

The first beat of the tachycardia is normally conducted, the other three are conducted with LBBB. While the initiating beat is atrial, of the same morphology as the SVEBs in the strip on this page(and similar to sinus P waves), the other three seem different, even allowing for their superimposition on the T wave or the ST segment. They may, therefore, have been produced by a reentry circuit at the atrial or junctional level. There is no certainty here, except to say the run is definitely supraventricular and the ‘lidocaine reflex’ should have been held in abeyance.

The LBBB S waves are truncated by the monitoring stylus range. The ST segment elevation of the sinus beats and the SVEBs probably reflects the anteroseptal infarction the patient is known to have had. Great caution is advised in interpreting rhythm strips’ repolarisation changes on their own; the filtering characteristics of monitor systems are often quite different from standard 12-lead ECGs.