Defibrillators Arrhythmia 1 Cardiac Pacing, Artificial 1 Cardiac pacing 1 Cardiovascular Diseases 1 Cardiovascular medicine 1 Congestive heart failure 1 Defibrillators, Implantable 1 Diseases 1 Electric Stimulation Therapy 1 Electrical Equipment and Supplies 1 Electrodes 1 Electrodes, Implanted 1 Equipment and Supplies 1 Health & Biological Sciences 1 Heart Diseases 1 Implantable cardioverter-defibrillators 1 Medicine 1 Prostheses and Implants 1 Therapeutics 1 Ventricular Dysfunction 1 Ventricular Dysfunction, Left 1