Abstract 2135: Correlation between Resting Heart Rate and Defibrillation Energy Threshold in Patients Undergoing Implantable Cardioverter Defibrillator Device Implantation

To investigate the association between resting heart rate (HR) and defibrillation threshold (DFT) in patients (pts) undergoing ICD implantation. DFT testing is usually considered standard of care during ICD implantation. However, the risk factors for high DFTs remain ill defined and the extent of testing required at implant has not been well defined. Baseline HR has been associated with higher DFTs in prior studies. We studied 128 pts undergoing ICD implantation. Baseline HR and DFTs were determined. HR was determined using ECGs obtained in the resting position on the day of ICD implantation. DFT testing was done during ICD implantation. We excluded 13 pts who were on amiodarone. The baseline characteristics of pts in the study are shown below in the table below (values in parenthesis represents standard error of the mean): First, a multivariate analysis of the association between baseline HR and DFT was performed, adjusting for left ventricular ejection fraction (LVEF), gender, body surface area (BSA) and beta blocker therapy. For every 10 beat increase in heart rate, DFT increased by 1 joule (p=0.02). Gender and beta blocker therapy did not effect this association. Second, pts were dichotomized based on DFTs to low (<15 joules) and high (≥15 joules). Mean resting HR was significantly higher among pts with high DFT (79 bpm) compared to those with low DFT (70 bpm) after adjusting for LVEF and BSA (p=0.01). Baseline resting HR is a risk factor for high DFT and may help define a higher risk pt population undergoing DFT testing.