Clinical Application of Electrocardiographic Imaging in Patients with Ischemic Cardiomyopathy, Early Repolarization Syndrome and Brugada Syndrome

Electrocardiographic Imaging (ECGI) is a noninvasive modality for human application in both research and clinical settings. It is an important tool for investigation of abnormal electrophysiological (EP) substrates and arrhythmias in patients. Multi-channel body surface potential recordings and the patient-specific heart-torso geometry from ECG gated computed tomography are processed by ECGI algorithms to reconstruct epicardial potentials, electrograms and patterns of activation and repolarization. ECGI is able to continuously generate high-resolution, panoramic EP maps of the entire heart on a beat-by-beat basis, which cannot be achieved with invasive catheter mapping. ECGI was applied in ischemic cardiomyopathy patients to characterize the abnormal EP substrate associated with myocardial infarction. In patients who developed ventricular tachycardia during the study, the arrhythmia activation pattern and site of origin were correlated with the EP substrate to identify components of the reentry circuit. The study subjects included patients with and without a history of clinical ventricular arrhythmias. The properties of scar EP substrate were compared between the two groups to determine whether substantial differences exist. This differentiating capability of ECGI was examined as a potential tool for arrhythmic risk stratification in this population. In a separate clinical study, ECGI was applied in a group of patients with early repolarization syndrome, which has been recently shown to be associated with an increased risk of ventricular fibrillation. The ventricular activation and repolarization patterns during sinus rhythm were characterized and compared with data from normal controls. This study aimed to provide insights into the mechanisms of the early repolarization ECG pattern and the related arrhythmogenesis. ECGI was also applied in patients with Brugada syndrome to image the EP substrate and to study the underlying mechanisms of the Brugada ECG pattern and abnormal epicardial electrograms. Heart rate change protocol in selected patients helped unmask the coexistence of abnormal conduction and abnormal repolarization in the EP substrate. Brugada syndrome patients were also compared with patients with right bundle branch block (generally considered benign) to determine whether the substrate was specific to Brugada syndrome, and whether ECGI can differentiate between these two pathologies with similar ECG patterns. The above studies demonstrated the feasibility and clinical importance of ECGI for noninvasive diagnosis, pre-procedural guidance and arrhythmic risk stratification in human subjects