Ventriculophasic Sinus Arrhythmia

Report:

Sinus rhythm.

Second degree AV block, Möbitz 1

Ventriculophasic sinus arrhythmia.

Phasic aberrant conduction

Comment:

The “short” complexes are aberrantly conducted sinus beats. The promotion from 2:1 to 3:2 block has produced a long-short cycle sequence required for phasic aberrant conduction. The diminished S wave during aberrant conduction is the earliest sign of RBBB aberrancy in V119.

Another long-short event here is, of course, the transient switch to 3:2 conduction in the middle of the strip, producing two short QRS cycles.

The third long-short phenomenon here is seen in the P wave cycle alternation during 2:1 conduction - the ventriculophasic sinus arrhythmia. The P waves surrounding a QRS complex are closer together than those with an “empty” cycle. The alternation is broken by the two periods of 3:2 conduction, eliminating 3:2 sinoatrial Wenckebach exit block as the cause of P wave bigeminy.

The ventriculophasic sinus arrhythmia may coexist with respiratory or non-respiratory variety. Its mechanism is unknown and several theories have been proposed.20

Fig 25. 51 year old hypertensive female treated with digoxin and verapamil for postoperative atrial fibrillation. When the surgeon asked his Registrar whether the therapy was successful, the latter said: “Yes and no”. This was true, but enraged the surgeon, and further explanation became necessary.