Arrhythmias refer to the disruption of the natural heart rhythm. This irregular heart rhythm causes the heart to suddenly stop pumping blood. Arrhythmias increase the risk of heart attack, cardiac arrest and stroke. Atrial pathologies are the most common arrhythmias with atrial fibrillation and atrial flutter being the most prevalent. The number of individuals with atrial fibrillation in the United States is expected to reach 12 million by 2050 since the prevalence increases with aging. Atrial flutter, often a result of ablative treatment, is also expected to rise as more of these treatments are administered. On the other hand, ventricular arrhythmias such as ventricular tachycardia and ventricular fibrillation denote extremely fast and chaotic rhythms, respectively, and can cause sudden cardiac death. This is partly because there is currently no noninvasive diagnostic imaging of arrhythmias. On the therapeutic front, in addition to pharmacological treatment, the first line of treatment of most arrhythmias is direct current cardioversion (DCCV), which denotes electrical defibrillation of the heart to reinstate its sinus rhythm. Despite the fact that DCCV remains highly successful in the short-term, it remains very difficult to determine which subjects will revert to their arrhythmias within the first 24 hours of treatment and will have to return to the healthcare premises for additional cardioversions that, apart from the inconvenience to the patient, result in major life disruption, pain and distress. When pharmacological treatment or cardioversion fail, radiofrequency (RF) ablation (RFA) is warranted, which currently constitutes a lengthy procedure (2-4 h/session) with a 55% success rate and thus often leading to repeated treatments to typically correct prior, incomplete ablations. An imaging technique to better inform on treatment response is thus warranted. To address the urgent need for noninvasive arrhythmia mapping, our group has pioneered Electromechanical Wave Imaging (EWI) that characterizes the electromechanical function throughout the four cardiac chambers to both identify the arrhythmic source (if applicable) but also inform treatment response. Should the findings of the proposed study indicate high reliability in guidance of clinical procedures, this novel imaging technology could be readily implemented in a clinical setting as part of a standard echocardiogram in order to increase the currently low time- and cost-efficiency as well as success rates of arrhythmia treatment.