Sudden cardiac death results from an abrupt loss of heart function (cardiac arrest). The victim may or may not have diagnosed heart disease. About 310,000 people a year die of coronary heart disease (CHD) without being hospitalized or admitted to an emergency room. This is about half of all deaths from CHD . about 850 Americans each day, i.e., about 1 American every 2 minutes. Despite this enormous death toll, there is currently no imaging modality in the clinic that can directly and noninvasively map the conduction wave in the entire heart or its disruption in the presence of an abnormality or disease. The ability to non-invasively image conduction in the failing heart would thus significantly improve the diagnosis, treatment, and management of this condition. In this study, our objective is to develop and evaluate a novel imaging modality, Electromechanical Wave Imaging (EWI) that can simultaneously map, at very high frame rates, both the electrical and mechanical cardiac function, at both the presence and absence of disease. We propose thus to demonstrate that the EWI technique can reliably map the conduction wave in the heart as it propagates along the septal wall and into the left and right ventricular walls;in both normal and pathological hearts. To assess the performance of the technique, we will use a novel electromechanical model, which will be extended and modified to fit the objectives of this study. The specific aims of the proposed study are thus to: 1) optimize the EWI estimates using an electromechanical canine simulation model;2) assess the performance of EWI in dogs with normal conduction and bundle branch block in vivo;and 3) validate the electromechanical wave imaged in vivo using the canine simulation model. As a result, the outcomes of this study are expected to yield a novel imaging methodology for noninvasive conduction mapping of the heart, at no or little additional cost to that of standard echocardiography, as well as simultaneously enrich the computation models of the electromechanical coupling of the heart. The high impact of this R21 application lies in the fact that the same imaging modality can easily be integrated into any commercial echocardiography system for immediate translation to the clinic. Furthermore, it can also be applied safely and noninvasively in conjunction with any diagnostic method, such as electrocardiography and echocardiography or, monitoring of therapeutic techniques, such as Cardiac Resynchronization Therapy (CRT) and radio-frequency (RF) ablation, for the detection and treatment of a wide range of cardiovascular diseases, or conditions, such as arrhythmias and heart failure. The high risk component is associated with the fact that tying the electrical with the mechanical function of the heart can be a formidable, but feasible given the team assembled and preliminary results available, challenge. PUBLIC HEALTH RELEVANCE STATEMENT: About 310,000 people a year die of coronary heart disease without being hospitalized or admitted to an emergency room. This is about 1 American every 2 minutes. Despite this enormous death toll, there is currently no imaging modality that can display the conduction wave in the entire heart in the clinic. Our objective is to develop and evaluate a novel imaging modality, Electromechanical Wave Imaging (EWI) that can noninvasively map the cardiac conduction, at both the presence and absence of disease.