Respiratory & Ventriculophasic Sinus Arrhythmia

Report:

Sinus rhythm

Respiratory sinus arrhythmia

Ventriculophasic sinus arrhythmia

Second degree AV block, Möbitz 1

Period of 2:1 conduction + one 5:4 cycle

LVH with ST/T changes ± digoxin effect

Comment:

The ventriculophasic effect – P-P intervals shortened with a QRS between the two P waves – is best seen around the third QRS complex. Its mechanism is poorly understood82. Respiratory sinus arrhythmia is also marked and modifies the ventriculophasic one elsewhere.

The QT interval is short for the initial ventricular rate of 37/min seen during the 2:1 conduction. The entire trace – the AV block, the evidence of increased vagal tone, the ST segment sagging, the QT interval - could be explained by digoxin effects and toxicity. The patient was, however, not on digoxin. Fewer and fewer patients are, nowadays: the diagnosis of “digitalis effect” is becoming, on Bayesian grounds, less and less attractive.

Below is an earlier trace (Fig 125a), showing bigeminy due to 3:2 Wenckebach (Möbitz 1) conduction. The blocked P waves, except for the first one, are hiding in the T waves.