Sleeper With No Apnœa

Report:

Sinus arrhythmia

Variable PR interval

Second degree AV block, unspecified

Single non-conducted P wave

Comment:

The block appears due to the respiratory variation of vagal tone and may have no more significance than a similar block induced in a healthy subject by carotid sinus massage or, for that matter, by sleep itself. This patient had a provisional diagnosis of sleep apnœa, where hypoxia, bradycardia and hypertension go hand-in-hand.

The rhythm strip excludes central sleep apnœa as the cause of the AV block, since there is a clear respiratory QRS variation. It does not exclude the obstructive variety, where respiratory efforts are present despite the absence of oronasal air flow4. This would of course affect the baseline, but not as smoothly as regular breathing in Fig 6 above. Observation of snoring and documentation of hypoxæmia by pulse oxymetry would have been of value while the patient was monitored in CCU.

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