Flutter Bigeminy

Report:

Atrial flutter 252/min 2

Alternating 2:1 & 4:1 block 2

Demand pacemaker 1

Pseudofusion spikes in alternate complexes 2

Small voltage, limb leads 1

Possible old anteroseptal infarction 1

Nonspecific ST/T changes 1

Comment:

The pacemaker rate is ostensibly 42/min, one spike for every 6 flutter waves. Its attempted pacing rate, judged from the distance of the preceding QRS, is 75/min. It must have sensed one QRS at some stage and became locked in a relationship with alternate flutter QRSs ever since. This relationship was never consummated in this tracing. It is, of course, a pure coincidence that the 4:1 flutter cycle and the pacing cycle happen to be the same length.

Flutter is one the more frequent sources of bigeminy (all that’s bigeminal isn’t extrasystolic, quoth Marriott24). The mechanism is quite simple: 2:1 + 3:2 two-level block.

Below (Fig 31a), the pacing spikes are more fruitful. Three of the beats are fusion beats and six are fully paced; no pseudofusion is present. The patient may have been better off with her native rhythm (and more effective narrow QRS complexes), but this remains unknown.

Fig 31a.

Fig 32. 73 year old man with permanent pacemaker, prone to somewhat irregular tachycardia.