Implantable Cardiac Defibrillators (ICDs) are at the forefront of preventing sudden death in patients suffering from ventricular arrhythmias. ICDs have evolved into complex Cyber-Physical Systems (CPS)which tightly sensing, hardware, and software to diagnose arrythmias based on electrogram signals and control cardiac excitation. These devices are life-critical, yet the Verification and Validation (V&V) techniques used for establishing their safety have remained somewhat informal, and rely largely on extensive unit testing. There have been a number of exciting developments in formal verification technologies. This proposal introduces these techniques into the ICD verification process, and will demonstrate their suitability for application in other medical devices. The project will develop a model-based framework for ICDs, and will apply formal verification techniques, such as model checking and reachability analysis, to high-fidelity cardiac electrophysiological models that capture the electrical excitation induced by the ICD's control software. Through extensive collaboration with FDA research staff, the proposal will demonstrate the effectiveness of formal verification technology and suitability in medical device applications.