Abstract 2496: High LDL Levels Predict Ventricular Fibrillation but Not Ventricular Tachycardia in Patients With Implantable Defibrillators
Introduction: In the implantable defibrillator (ICD) recipient, ventricular fibrillation (VF) necessitates delivery of defibrillation therapy but ventricular tachycardia (VT) can often be treated with painless overdrive pacing therapy. Abnormal serum lipoprotein levels appear to influence overall ventricular arrhythmia recurrence but associations with VF vs. VT recurrence have not been fully explored.
Methods: We conducted a sub-analysis in a cohort of the 200 ICD patients enrolled in a randomized, double-blind, placebo-controlled trial of fish oil vs. olive oil placebo at 6 US medical centers with enrollment from February 1999 until January 2003. The main sub-analysis predictor variables were low density lipoprotein (LDL) and high density lipoprotein (HDL) levels at study baseline. The main outcome variables were time to first ICD therapy for VT or VF, analyzed separately. Primary time-to-event analyses were performed using the Kaplan-Meier method. A Cox proportional hazards model was constructed to assess the significance of the primary outcome controlling for age, gender, and other baseline characteristics. All models were adjusted for treatment allocation to fish oil and placebo.
Results: Each 1 mg/dl increase in baseline serum LDL level was associated with a 2% increase in the risk of VF (p=0.027). HDL was not a significant predictor for VF (p=0.264). Neither LDL (p=0.844) nor HDL (p=0.842) were significant predictors for VT. Triglycerides were insignificant for both VF (p=0.488) and VT (p=0.864). Statin use did not confound the relationship between lipoprotein subfractions and ventricular arrhythmias.
Conclusions: Among this cohort of ICD patients, baseline serum LDL level was a significant predictor of VF but not VT. A possible explanation for this observation is an LDL effect on ischemia or inflammation, which would seem more likely to cause VF than VT. These findings also suggest the need for systematic evaluation of whether aggressive LDL lowering results in more treatable ventricular arrhythmias with significant implications for ICD patients.