Mapping the electrical activity of the heart in vivo using ultrafast acoustoelectric imaging

Abstract

The heart is driven by an electrical activation that propagates in cells and triggers their concerted contraction. When this electrical activation pattern is altered, it can lead to debilitating diseases such as arrhythmia or heart failure. Yet, directly imaging the electrical activity of the heart remains difficult to achieve. We have recently introduced Ultrafast Acoustoelectric Imaging (UAI) that combines ultrasound plane wave emissions and the acoustoelectric effect, i.e., the modulation of electrical impedance by ultrasound waves, to map electrical current densities in real-time with 1-mm and 5-ms spatial and temporal resolutions, respectively. Herein, we present its application to direct mapping of the cardiac activation in isolated live rat hearts and in pig hearts in vivo. UAI was performed in isolated rat hearts (n = 4) and in open-chest pigs (n = 1) using a 5-MHz linear array ultrasound probe fitted to a 256 channel- Vantage ultrasound system (Verasonics, Inc., WA). Two electrodes positioned on the heart and fed to the Vantage system were used to detect electrical impedance variations caused by ultrasound plane waves, which were then backprojected to reconstruct images of electrical current densities. UAI images depicted the propagation of the electrical activation of the cardiac tissue as validated by the electrocardiogram. These first in-vivo results suggest that UAI may allow the emergence of new biomarkers for the diagnosis and pre-clinical study of cardiac activation diseases such as arrhythmias.