Detection of the Cardiac Activation Sequence by Novel Echocardiographic Tissue Tracking Method

Abstract 

Asynchronous cardiac activation leads to decreased pumping efficiency. Quantifying the activation sequence may optimize both the selection of patients for cardiac resynchronization therapy (CRT) and its efficacy. The feasibility of assessing the directivity and the degree of synchronous activation with ultrasound was examined. A tissue tracking method (CEB, GE-Ultrasound, AFI, GE Healthcare Inc., Wauwatosa, WI, USA) provided the regional strain profiles. The first maxima in systole of the regional circumferential strains were considered as the activation times. An integrative vector (SDV) describes the activation synchrony and directivity. In six open-chest sheep, activation maps and SDV were calculated in short-axis planes of the left ventricle for normal activation and induced pacings from the anterior and lateral free walls. Both magnitude and angle of the SDV were statistically different (p < 0.05) for the different pacings. Localization of the pacing site was 3° ± 18° from true position. Conclusions were that motion analysis in echocardiograms provides insightful information regarding the activation process and may enhance procedures such as CRT. (E-mail: Dan@bm.technion.ac.il)

Key Words: Activation sequence, Tissue tracking, Strain imaging, Cardiac resynchronization therapy