Bigeminy and Trigeminy: Atrial Flutter

Report:

Atrial flutter 250/min

Alternating 4:1 & 2:1 (2:1 + 3:2) conduction, with bigeminy (top)

2:1 + 4:3 conduction, with trigeminy (bottom)

Comment:

Typical flutter has a basic 2:1 block and a more distal, Wenckebach block; this combination accounts for the preponderance of even overall conduction ratios in atrial flutter.

If one disregards every second F wave, the remaining ones can easily be configured into a 3:2 pattern of increasing F-to-R intervals before an F is dropped. Below, a trigeminy can be analogously interpreted as 4:3 Wenckebach conduction.

A famous dictum of Marriott's states that all that's bigeminal isn't extrasystolic11. Neither is all that's trigeminal.

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