This study evaluates whether the addition of tetanizing burst therapy reduces the pain associated with ICD shocks

The implantable cardioverter defibrillator is a device designed to rescue patients from life-threatening arrhythmias by delivering a defibrillation shock to allow restoration of cardiac rhythm. These defibrillation shocks are extremely painful, owing to sudden rapid contraction of thoracic and abdominal skeletal muscle, which, in addition to the heart, are stimulated by the defibrillation shock. Tetanizing Burst Therapy is a novel electrical waveform which tetanizes skeletal muscle with a brief burst of stimulation prior to the ICD shock, thereby reducing muscular contraction due to the shock. This study is designed for those patients who are already undergoing ICD replacement.

Inclusion Criteria:

• Male or Female age 18-80 years, inclusive
• Ability to understand and provide written informed consent
• Normal sinus rhythm
• Standard transvenous left-sided ICD referred for device replacement due to end of battery life

Exclusion Criteria:

• Heart rate <40 or >90 bpm
• Atrial fibrillation or pacemaker dependent
• NYHA Class III/IV symptoms of HF
• MI within 90 days of enrollment
• Severe cardiac ischemia manifested by chest pain at rest or with minimal exercise
• History stroke or TIAs
• History of prior ICD pocket infection
• ICD lead resistance that is too high or too low in the opinion of the investigator
• Female who is pregnant or breastfeeding
• Prior heart transplant
• Serum electrolytes out of normal range at participating institution