Discussion
We reported an anecdotal case of pararrhythmia with LFVT and ss AVNRT.
Co-existence of LPFVT and AVNRT in one patient is rare. They can occur
spontaneously at different times or be induced separately by atrial or
ventricular stimulation [2]. Extremely limited literatures reported
simultaneous LPFVT and slow-fast AVNRT after intravenous administration
of atropine [3]. The mechanism of the pararrhythmia was attributed
to two coexisting reentrant circuits with similar cycle lengths by
chance. During the procedure, it could be seen that the QRS complex
morphology alternately transformed among wide, narrow and fusive,
accompanied by change of HV interval that shortened or lengthened
following QRS complex widened or narrowed. This phenomenon indicated a
concurrent attack of two tachycardias, which should be distinguished
from supraventricular tachycardia with intermittent bundle branch block.
In the latter case, there shouldn’t be obvious shortening of HV
interval. Considering that both LPFVT and AVNRT were originated from the
AV conduction system, maybe there is an unconfirmed interaction between
the two kinds of arrhythmias.