Intracardiac myocardial elastography in humans in vivo during radio-frequency ablation

Abstract

Intracardiac echocardiography (ICE) is commonly used during radio-frequency (RF) ablation procedures for procedural guidance. Besides its imaging function, ICE could be used to assess mechanical properties of the myocardium to improve the ablation outcome. The objective of this study was to demonstrate the feasibility of imaging myocardial strains in vivo within the same imaging plane as ICE at high temporal resolution. A 5.8-MHz center frequency ICE probe was used to image the heart of two humans with atrial arrhythmias in vivo before and after RF ablation at high frame rates (1200 Hz), and the channel data were acquired on a clinical ultrasound system. The RF signals were reconstructed on a 9cm depth and 90° field of view region and axial cumulative displacement estimation was performed using 1-D cross-correlation using a window size of 2.6 mm and 95% overlap. Cumulative axial strains were obtained from the displacements using a least-squares estimator with a kernel of 5.1 mm. Cumulative axial strains in the left atrium during systole were 23% and 18% in the two subjects before ablation, changing to 8% and 11% in the same location after ablation. Myocardial elastography could thus provide some quantitative methods for monitoring the generation of thermal lesions.