Abstract 12981: Does Volume Overload Predict Failed Antitachycardia Pacing Therapy for Ventricular Tachycardia in Patients With an Implantable Cardioverter-Defibrillator?

Abstract

Introduction: Decompensated heart failure (HF) increases the risk of Implantable Cardioverter-Defibrillator (ICD) therapy. Patients with failed antitachycardia pacing (ATP) for ventricular tachycardia (VT) termination, requiring ICD shock, have been reported to have worse outcomes compared to patients with effective ATP. Thoracic impedance (TI) is a diagnostic parameter found in many ICDs. In Medtronic devices, TI is transformed into a OptiVol index, which when elevated, may represent volume overload and can predict increased HF events. Hypothesis: Whether an elevated OptiVol index is associated with failed ATP for VT termination in ICD patients. Method: Retrospective review of a prospectively collected database of patients followed in a dedicated ICD clinic, enrolled in remote ICD monitoring and who received therapy for VT termination by an OptiVol-capable ICD. The level of OptiVol was measured near the time of VT events. VT events were divided into two groups: OptiVol index <100 and OptiVol≥100, and distributions of successful and unsuccessful ATP were compared. Results: We analyzed 121 VT episodes that occurred in 39 ICD patients who received ATP or shock to terminate VT. Mean age of patients was 68.4 +/- 10 years and 32 patients (78%) were male. Ischemic cardiomyopathy was present in 20 patients (48.8%). Successful ATP was more likely when the VT event was associated with an OptiVol index <100 (74.5% successful vs 25.5% unsuccessful, P<0.001); whereas a VT event associated with an OptiVol≥100 was more likely to be unresponsive to ATP compared with ATP success (66.7% unsuccessful vs 33.3% successful, p<0.001). Conclusions: Failed ATP, requiring shock therapy for VT, is associated with a measure of volume overload (OptiVol) and could explain the worse outcomes observed in patients who require ICD shocks.