Three Causes of Pauses & Many Diagnoses

Report:

Sinus rhythm 88 - 92/min

Left atrial abnormality (LAA)

P wave 0.12”

SVEB, non-conducted

VEBs, late-diastolic

Ventricular fusion beat (third last complex in the bottom strip)

Junctional escape (top strip) and premature beat (bottom strip), RBBB aberrancy

Möbitz 1 (Wenckebach) AV block

Comment:

The late-diastolic VEBs in the top strip replace not one, but two sinus beats; in the bottom strip, the last abnormal beat is intermediate in shape between pure VEBs and the sinus beats - a fusion complex.

The second abnormal beat in the bottom strip is probably a junctional one with RBBB aberrancy, perhaps “forced” by the preceding VEB. It may also be a qR VEB superimposed n the sinus P wave, a second VEB of a couplet. It cannot be a fusion beat - the sinus P wave is practically inside it.

The initial group of 4 beats in the bottom strip is an aborted Wenckebach sequence, terminated not by a blocked P wave but by a blocked P’ wave of an atrial ectopic, peaking the T wave of the fourth beat. This blocked P’ may also, in view of the long preceding PR interval, be a reentry (echo) beat of sinus origin.

The three causes of pauses are, therefore, VEBs (replacing two sinus cycles each), blocked SVEB and Wenckebach periods.

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