Atropine Bradycardia

Report:

Top:

Sinus rhythm 83 - 85/min

Second degree AV block

Escape-capture bigeminy

Ventricular rate 55/min

Bottom:

Sinus tachycardia 100/min

2:1 AV block

Ventricular rate 50/min

Comment:

In the top strip, a basic 2:1 AV block is modified by the junctional escape beats, which prevent conduction of every third P wave and produce the escape-capture bigeminy. The slowing of the ventricular rate attending atropine-induced sinus tachycardia is due to the change in the overall P:QRS ratio from 3:2 to 2:154. This is not, of course, the paradoxical response allegedly associated with small doses of atropine, which consists of slowing of the sinus rate through stimulation of medullary vagal nuclei55.

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