The Harvard-Thorndike Electrophysiology Institute and Arrhythmia Service at BIDMC is the oldest and largest program of its kind in the region. Staff were among the pioneers of modern cardiac electrophysiology, and continue cutting-edge research. Attracting patients nationally and worldwide, with about 7,000 visits annually in the arrhythmia and pacemaker/device clinics, the service offers advanced diagnosis and treatment modalities.