Paced Escape - Paced Capture Bigeminy

Report:

Sinus rhythm 57/min 0.5

Complete AV dissociation 0.5

Fixed pacemaker rhythm 31/min 3

Demand pacemaker escape rhythm (set at) 60/min 3

Escape-capture bigeminy 3

Comment:

The original pacemaker continued to fire at 31/min as before, obviously devoid of any capacity to sense the additional beats from the temporary pacemaker. If it could sense them, it would be completely suppressed by the twice as fast temporary unit. The temporary pacemaker escapes exactly one second after a sensed permanent pacemaker’s beat – it was set at 60/min. This creates both preconditions required for the development of escape-capture bigeminy: (i) marked discrepancy in cycle length – one versus two seconds; and (ii) protection of the slow pacemaker from the faster one’s impulses. This protection is in this case afforded by the old pacemaker’s loss of sensing56.

This is an unusual instance of escape-capture bigeminy, a rhythm commonly seen in profound sinus bradycardia or effective sinus bradycardia created by a partial AV block; the escape beats are junctional or ventricular, or paced. This case has both escape and capture beats generated by electronic pacemakers.

The conjunction of the two pacemakers is, as Marriott put it, an arithmetical caprice57.

This patient had of course a new permanent unit implanted, using the same electrodes, and the temporary wire was withdrawn.