Onset of Pacing With Retrograde Conduction

Report:

Sinus rhythm 59-62/min 1

Borderline left atrial abnormality (LAA) 1

Demand pacemaker rhythm 59/min 3

Retrograde conduction 5

Comment:

The slight sinus arrhythmia allows the pacemaker takeover at 59/min, following a pseudofusion beat in the middle of the trace. This is where rate hysteresis could have been useful.

What keeps the sinus rhythm in abeyance is the retrograde conduction to the atria. This may lead to drop in stroke volume and the cardiac output, which in turn may be expected to accelerate the sinoatrial impulse formation and allow the sinus rhythm to resume control (Fig 34a).

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