Minimally-invasive treatments of cardiac arrhythmias such as radio-frequency 
ablation are gradually gaining importance in clinical practice but still lack a 
noninvasive imaging modality which provides insight into the source or focus of 
an arrhythmia. Cardiac deformations imaged at high temporal and spatial 
resolution can be used to elucidate the electrical activation sequence in normal 
and paced human subjects non-invasively and could potentially aid to better plan 
and monitor ablation-based arrhythmia treatments. In this study, a novel 
ultrasound-based method is presented that can be used to quantitatively 
characterize focal and reentrant arrhythmias. Spatio-temporal maps of the 
full-view of the atrial and ventricular mechanics were obtained in a single 
heartbeat, revealing with otherwise unobtainable detail the electromechanical 
patterns of atrial flutter, fibrillation, and tachycardia in humans. During 
focal arrhythmias such as premature ventricular complex and focal atrial 
tachycardia, the previously developed electromechanical wave imaging methodology 
is hereby shown capable of identifying the location of the focal zone and the 
subsequent propagation of cardiac activation. During reentrant arrhythmias such 
as atrial flutter and fibrillation, Fourier analysis of the strains revealed 
highly correlated mechanical and electrical cycle lengths and propagation 
patterns. High frame rate ultrasound imaging of the heart can be used 
non-invasively and in real time, to characterize the lesser-known mechanical 
aspects of atrial and ventricular arrhythmias, also potentially assisting 
treatment planning for intraoperative and longitudinal monitoring of 
arrhythmias.