B-PO05-211 PROGRAMMING CHALLENGES DURING LEFT VENTRICULAR PACING. A CASE OF PACEMAKER-MEDIATED TACHYCARDIA

Abstract

Multichamber pacing may be associated with complex interactions between pacing timing cycles. Review of a case of pacemaker mediated tachycardia (PMT) during LV pacing. Data was collected by retrospective review. A patient with a history of coronary artery disease and bypass surgery, heart failure and primary prophylaxis dual chamber defibrillator (ICD) underwent upgrade to a biventricular ICD (Boston Scientific Vigilant X4 G247) due to new left bundle branch block and heart failure symptoms. Postoperative programming was identical (DDDR 50/130/130 bpm; PVARP 240-280 ms) except for shortened AV delay with simultaneous RV/LV pacing. During an admission to an outside hospital, AV delay was shortened (SAV: 100 ms, PAV 150 ms) and pacing mode was changed to LV only. In follow-up, numerous PMT episodes were noted in the device memory (Panel A) and also during device interrogation but only with LV-only pacing. Retrograde P wave during LV pacing fell outside the programmed PVARP because retrograde left bundle branch block caused transseptal retrograde conduction via the right bundle branch with delay in LV to RA interval. Timing from RV apex to RA (Panel B, red arrow, 240 ms) was the same during RV pacing and during LV pacing (panel C) but because PVARP is initiated with the first paced ventricular chamber, the V to A time prolonged with LV-only pacing (Panel C, blue arrow, 420 ms) beyond PVARP. Programming very long PVARP limits upper tracking rate so in this case we switched to biventricular pacing which shortened the QRS duration and also eliminated PMT episodes. In CRT devices, PVARP should be reassessed when LV only pacing is programmed.