Impact of Upgrade to Cardiac Resynchronization Therapy on Ventricular Arrhythmia Frequency in Patients With Implantable Cardioverter-Defibrillators

Impact of Upgrade to Cardiac Resynchronization Therapy on Ventricular Arrhythmia Frequency in Patients With Implantable Cardioverter-Defibrillators Cengiz Ermis, Ryan Seutter, Alan X. Zhu, Lauren C. Benditt, Laura VanHeel, Scott Sakaguchi, Keith G. Lurie, Fei Lu, David G. Benditt The frequency of ventricular tachyarrhythmias and implantable cardioverter-defibrillator (ICD) shocks was compared before and after upgrade of conventional ICDs to cardiac resynchronization therapy (CRT)-ICD in patients being treated for heart failure associated with left ventricular systolic dysfunction. After CRT-ICD placement, ventricular tachyarrhythmia frequency (particularly ventricular fibrillation), as well as the number of appropriate ICD therapies, were markedly diminished, supporting the view that CRT may ameliorate arrhythmia susceptibility in heart failure patients. This study compared cardiac resynchronization therapy’s (CRT) impact on ventricular tachyarrhythmia susceptibility in patients who, due to worsening heart failure (HF) symptoms, underwent a replacement of a conventional implantable cardioverter-defibrillator (ICD) with a CRT-ICD. Cardiac resynchronization therapy is an effective addition to conventional treatment of HF in many patients with left ventricular systolic dysfunction. However, whether CRT-induced improvements in HF status also reduce susceptibility to life-threatening arrhythmias is less certain. Clinical and ICD electrogram data were evaluated in 18 consecutive ICD patients who underwent an upgrade to CRT-ICD. Pharmacologic HF therapy was not altered during follow-up. The definition of ventricular tachycardia (VT) and ventricular fibrillation (VF) for each patient was as determined by device programming. Statistical comparisons used paired ttests. Findings were recorded during two time periods: 47 ± 21 months (range 24 to 70 months) before and 14 ± 2 months (range 9 to 18 months) after CRT upgrade. At time of upgrade, patient age was 69 ± 11 years and ejection fraction was 21 ± 8%. Before CRT the frequency of VT, VF, and appropriate ICD shocks was 0.31 ± 1.23, 0.047 ± 0.083, and 0.048 ± 0.085 episodes/month/patient, respectively. After CRT-ICD, VT and VF arrhythmia burdens and frequency of shocks were respectively 0.13 ± 0.56, 0.001 ± 0.004, and 0.003 ± 0.016 episodes/month/patient (p = 0.59, 0.03, and 0.05 vs. pre-CRT). Arrhythmia frequency and number of appropriate ICD treatments were reduced after upgrade to CRT-ICD for HF treatment. Thus, a