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.
