Empty Wenckebach Pauses

Report:

Sinus rhythm

SVEB (second QRS, bottom strip)

Second degree AV block, Möbitz 1

Junctional beats, non-conducted

?Reentry beats of sinus origin

Atrial fusion beats, non-conducted

Comment:

In the upper strips, the Wenckebach sequences are terminated by retrograde P’ waves of opposite polarity to sinus P waves. They may well be reentry (echo) beats propitiated by the prolonging PR intervals. At any rate, their timing allows atrial fusion with sinus P waves - fusion so perfect in some of the cycles that the pause looks ‘empty45’ - totally bereft of any atrial activity! In fact the pause is crowded. A little wrinkle in the baseline can just be made out in the right place when looked for.

There is some sinus arrhythmia.

This patient’s 12-lead ECG, with a masquerading bundle branch block, is shown below. It is one of the causes of concordant precordial pattern.

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