Non-invasive Electromechanical Wave Imaging of atrial, supraventricular and ventricular cardiac conduction disorders in canines and humans

Electromechanical Wave Imaging (EWI) is a novel ultrasound-based imaging modality for the mapping of the electromechanical wave (EW), i.e., the transient deformations occurring in immediate response to the electrical activation. The correlation between the EW and the electrical activation has been established in canines in previous studies. However, the methods used previously to map the EW required the reconstruction of images over multiple cardiac cycles, precluding the application of EWI for non-periodic arrhythmia such as fibrillation. In this study, we present a new unfocused sequences based on flash emissions to image the entire heart at very high frame rates (2000 fps) during free breathing in a single heartbeat and compare it to the automatic composite technique (ACT), which is based on acquisition spanning multiple heart cycles and is used to image normal human subjects during sinus rhythm. Feasibility of flash-beam sequences is assessed by imaging the atria and ventricles of closed-chest, conscious canines during sinus rhythm and during right-ventricular pacing following atrioventricular dissociation, i.e., a non-periodic rhythm and during ventricular fibrillation in one open-chest canine. These results indicate that EWI can be used for the characterization of non-periodic arrhythmia in conditions close to the clinical setting, in a single heartbeat, and during free-breathing.