Project Summary Implantable Cardioverter/defibrillators (ICDs) have been proven to the most effective therapy to reduce mortality from sudden cardiac death. Today?s ICD technology exclusively relies on sophisticated algorithmic analysis of cardiac electric signals (electrograms, EGM) sensed by the ICD to detect fatal cardiac arrhythmias, such as ventricular tachycardia (VT) and ventricular fibrillation (VF), that trigger discharge of electrical energy (ICD shock) to restore normal rhythm. Despite decades of continuing effort and incremental technological advances, inappropriate shock (IAS), erroneously triggered by nonfatal events, remains a significant problem and represents an unmet clinical need. IAS often occurs during nonfatal events that are associated with stable hemodynamic status and most commonly include (1) electrical noises, from electromagnetic interference (external noise) or ICD lead fracture (internal noise), and (2) nonfatal tachyarrhythmias (TA) such as hemodynamically stable atrial fibrillation (AF) with rapid ventricular response . The objective of the project is to test the feasibility and eventual commercialization of an innovative technology with fiber optic sensors in the existing ICD system that assess the hemodynamic stability during arrhythmias and thereby reduce IAS. The proposed research in Phase I is to evaluate the feasibility of this novel technology in a swine model to determine hemodynamic stability during tachyarrhythmia, thereby separating hemodynamically stable TAs from those that are unstable, and will specifically focus on testing the feasibility of optical sensors embedded in the existing ICD system in assessing hemodynamics through detecting changes in cardiac strain parameters (Aim 1), the feasibility of such optical sensors in identifying electrical noises based on unchanged hemodynamics (Aim 2), and the feasibility of such optical sensors in differentiating hemodynamically stable AF with rapid ventricular response from unstable AF and from ventricular fibrillation (Aim 3).