VVI Pacemaker Mime of Atrial Sensing

Report:

Pacemaker rhythm 70/min 4

Atrial tachycardia/flutter 210/min 6

Comment:

The patient had a VVI pacemaker set at 70/min, precisely because she had almost constant atrial tachyarrhythmias. In this tracing, however, the AV interval appears fixed at approximately 0.16”, giving an illusion of atrial sensing.

Below is another example (Fig 95a), but with an AV interval of 0.28”. In both ECGs the atrial rate is almost exactly three times the ventricular one, giving an illusion of cause and effect. All we can be sure of, as David Hume would remind us50, is contiguity and succession – causes as such are only inferred. In this case, wrongly! I am not sure whether accrochage51 works with rhythms other than sinus. The bottom trace (Fig 95b), taken at another time, shows the expected AV dissociation.

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