Title : Recurrent syncope late after permanent pacemaker implantation -
What is the mechanism?
Abstract
A 68-yr-old lady underwent a VVI pacemaker implantation 10 years back
for infra-hisian complete heart block. Now she presents with 3 episodes
of syncope within the last 2 months. Detailed neurological evaluation
and pacemaker checkup was initially unremarkable. Real time electrograms
during device interrogation were suspicious of lead noise resulting in
oversensing. She became alright when the pacing mode was made VOO
immediately. After discussion with patient relatives she underwent
ventricular lead replacement and upgradation to a dual chamber
pacemaker. However, in the immediate post-operative period she became
unresponsive requiring immediate resuscitation. Monitor suggested short
runs of polymorphic VT which was reproducibly suppressed with higher
rate obligatory pacing @ 110 bpm. The runs of VT resurfaced immediately
as the rate was lower than 90. She was managed by overdrive pacing at a
lower rate of 110 bpm. Over the next 2 months the lower rate was brought
down to 70 bpm in a stepwise manner. A retrospective analysis of her
initial stored device electrogram suggested that it was all PMVT and no
noise at all. The cause of her polymorphic VT is not clear. Relative
hypomagnesemia, late presenting long QT syndrome and long term VVI
pacing in isolation or combination remain the probable offender. She is
presently doing well on oral propranolol.