Overdrive of Atrial Tachycardia With Block

Report:

Top:

Atrial tachycardia 200/min 1

2:1 AV block 1

Pacemaker artefact 122/min 2

No capture 1

Second:

Atrial pacing 250/min 3

Capture 0

Variable AV block 0.5

Third:

Atrial pacing 80/min 0.5

1:1 conduction 0

Bottom:

Sinus rhythm 68/min 1

Comment:

The initial underdrive pacing is part of the protocol designed to recognise possible ventricular captures before the really fast rates are applied. Atrial capture would be recognised too (given the rate of 200/min and large, distinctive atrial waves); sometimes it suffices to break the tachycardia (underdrive pacing). The last pacing spike in the top strip has, in fact, effected a capture, but did not break the tachycardia. The capture may have been an atrial fusion beat.

Maintenance of the restored sinus rhythm depends most of all on the patient’s continued improvement. I prefer not to use antiarrhythmic agents unless there is a recurrence or if the paroxysms cause severe hæmodynamic impairment.

The above technique was new in the ACT in 1979 and I had to watch my step carefully.