Electromechanical wave imaging for arrhythmias

Abstract

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 previous studies. However, the methods used previously to map the EW required the reconstruction of images over multiple cardiac cycle, precluding the application of EWI for non-periodic arrhythmia such as fibrillation. In this study, we develop new imaging sequences based on flash and wide-beam emissions to image the entire heart at very high frame rate (2000 fps) during free breathing in a single heartbeat. The methods are first validated by imaging the heart of an open-chest canine while simultaneously mapping the electrical activation using a 64-electrode basket catheter. Feasibility is then 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. The EW was validated against electrode measurements in the open-chest case, and followed the expected electrical propagation pattern in the closed-chest setting. 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.

Assessing the Stability of Aortic Aneurysms with Pulse Wave Imaging

“…which means that lower frequencies and lower frame rates must be used; and the limited acoustic window in some areas, which necessitates the use of diverging beams and implies that lateral resolution decreases with depth. However, human aneurysms are also commensurately larger than the murine ones in this study, and recent work with modern imaging platforms has demonstrated that comparable beam densities, relative to the size of the aneurysm, are possible in humans (34). This work therefore suggests additional parameters to consider that may be correlated with disease outcome and that clinicians may consider on a case-by-case basis when assessing patients.…”

Stolt's f-k migration for plane wave ultrasound imaging

“…4). The travel-time (5) thus becomes: (6) Now, let (α, β, γ) be constant parameters defined by the following equations:…”

“…The ERM in conjunction with the transformations defined by (7) and (9) can thus be used to model tilted PWI. The difference between the travel-times given by (6) and (8) …”

“…Recent studies indicate the growing emergence of ultrasound plane wave imaging (PWI). This technique has proven itself as a reliable method in several original and promising applications such as transient elastography, ultrafast Doppler imaging, ultrafast vector flow mapping, electromechanical wave imaging and functional brain imaging [3][4][5][6][7].…”

Feature Tracking Algorithm for Circumferential Strain using High Frame Rate Echocardiography

“…In order to appreciate these events a temporal resolution of close to 2 ms would be necessary [1]. In the last decade propagating events have been noted in vivo using different US modalities such as Tissue Doppler Imaging (TDI) and B-mode [2][3][4][5][6][7][8][9][10]. These studies all use velocity curves to describe the electromechanical coupling.…”