Sinus Arrhythmia or SA Exit Block?

Report:

Sinus rhythm

Sino-atrial exit block

Comment:

All the groups display the characteristic acceleration before the pause. This is the hallmark of Wenckebach (Möbitz 1) sino-atrial exit block, only slightly modified by true (respiratory) sinus arrhythmia. Normal young people may develop a range of bradyarrhythmias commonly assumed to be abnormal, especially in their sleep. This one also had a closed head injury.

This is not enough to make one reach for the pacemaker. It has no prognostic significance with respect to the outcome of the head injury, either.

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