Atrial Flutter with High-Grade AV Block

Report:

Atrial flutter 260/min

Advanced (high-grade) AV block

Possible junctional escape beats

Nonspecific ST/T changes

Comment:

Complete block is excluded by the irregularity of the admittedly slow ventricular rate. Furthermore, one looks for the shortest cycles for conduction (capture beats are always early, quoth Marriott); the second and the fourth are identical, down to the position of F wave half-buried in the terminal portion of the QRS complex. The third and the seventh cycles are not the same length, but have the same F-R intervals (again, it helps to look at the F wave behind the QRS to time its predecessors, since it is etched on the repolarisation timeline.

The longest, fifth, cycle may well be terminated by a junctional escape beat, but there is no certainty there.

Below (Fig 56a) is a trace in fixed 4:1 block (some pedants would insist on calling it 4:1 conduction, strictly speaking more accurately). The conducted F waves are not those immediately in front of the ventricular complexes, but the ones preceding them – a common example of “skipping” or “over the top” conduction in flutter. The F-R interval in flutter is usually about 0.40”.

Fig 56a. Atrial flutter with 4:1 block. Prominent U wave is seen in V4, for any of the (un)known reasons.

Fig 57. Holter recording of 47 year old lady with no cardiac history, asleep. She complained of palpitations during the day.