Trigeminal Bradycardia

Report:

Sinus tachycardia

Advanced second degree AV block

9 second pause

Junctional escape beats

Comment:

Some sinus beats are probably conducted, e.g., first two in the top strip. The long pause is terminated by a junctional escape (first beat in the middle strip). The escape pacemakers were obviously sluggish; she required ventricular pacing for 48 hours. The junctional QRSs are slightly but definitely taller than the sinus beats – another example of what Schamroth calls non-phasic aberrant conduction. The aberration is most likely due to a different activation front reaching the ventricles from a junctional focus.

The obvious question is why should a healthy 42 year old develop high-grade AV block following a craniotomy for trigeminal decompression. She was not taking carbamazepine, a potential cause of AV block. The recorded examples of trigeminal nerve stimulation resulting in bradycardia83,84 involve sinus bradycardia or arrest, rather than sinus tachycardia seen in this example. This is most likely a case of congenital heart block unmasked by anæsthesia and surgery.

A Holter study three weeks after surgery showed borderline PR interval 0.20” and four episodes of second degree AV block, each consisting of a single dropped P wave.