Sinus Captures with 1o AV Block

Report:

Sinus rhythm approx. 86/min 1

Second degree AV block, unspecified 2

AV pacemaker rhythm 60/min 1

No atrial capture 2

Sinus captures with 1o AV block 2

Left anterior hemiblock + IVCD 1

LVH with ST/T changes 1

Comment:

The space between the atrial and the ventricular spikes is empty except for the fourth cycle, where a sinus P wave, too close to the ensuing QRS to be conducted, is seen – and sensed, causing the ensuing paced QRS. The sinus P waves are faster than the pacemaker and somewhat irregular, perhaps due to respiratory or ventriculophasic sinus arrhythmia.

In the rhythm strip, sinus captures are distinguished from the paced beats by being narrower and having a sharp S descent; the paced beats have the characteristic delayed descent in V1. An atrial pacing spike is interposed between each sinus capture and its QRS. The latter may be called a pseudo-pseudofusion beat!

The patients AV conduction was impaired even before the aortic valve replacement: below is a preoperative ECG with Wenckebach 2o AV block (Fig 101a).