Intracardiac acoustic radiation force impulse imaging: A novel imaging method for intraprocedural evaluation of radiofrequency ablation lesions

Abstract

Background Arrhythmia recurrence after cardiac radiofrequency ablation (RFA) for atrial fibrillation (AF) has been linked to conduction through discontinuous lesion lines. Intraprocedural visualization and corrective ablation of lesion line discontinuities could decrease post-procedure AF recurrence. Intracardiac acoustic radiation force impulse (ARFI) imaging is a new imaging technique that visualizes RFA lesions by mapping the relative elasticity contrast between compliant-unablated and stiff-RFA treated myocardium. Objective To determine if intraprocedure ARFI images can identify RFA treated myocardium in vivo. Methods In eight canines, an electroanatomical mapping (EAM) guided intracardiac echo catheter (ICE) was used to acquire 2D ARFI images along right atrial ablation lines before and after RFA. ARFI images were acquired during diastole with the myocardium positioned at the ARFI focus (1.5 cm) and parallel to the ICE transducer for maximal and uniform energy delivery to the tissue. Three reviewers categorized each ARFI image as depicting no lesion, non-contiguous, or contiguous lesion. For comparison, three separate reviewers confirmed RFA lesion presence and contiguity based on functional conduction block at the imaging plane location on EAM activation maps. Results Ten percent of ARFI images were discarded due to motion artifacts. Reviewers of the ARFI images detected RFA-treated sites with high sensitivity (95.7%) and specificity (91.5%). Reviewer identification of contiguous lesion had 75.3% specificity and 47.1% sensitivity. Conclusions Intracardiac ARFI imaging was successful in identifying endocardial RFA treatment when specific imaging conditions were maintained. Further advances in ARFI imaging technology would facilitate a wider range of imaging opportunities for clinical lesion evaluation.

Recent Advances in Lesion Formation for Catheter Ablation of Atrial Fibrillation

“…72 Furthermore, ARFI imaging can distinguish between an incomplete atrial ablation line with a gap and a complete ablation line. 70 The presence of a lesion in the ARFI image is predictive of a conduction disturbance at that location (positive predictive value=96.4% and negative predictive value=90.0%), and the finding of a gap in the ablation line by ARFI imaging predicts lack of conduction block (negative predictive value=71.2%). Finally, ARFI imaging has been successfully adapted to clinical ultrasound and mapping systems during routine clinical catheter ablation procedures with demonstrated feasibility of acquiring ARFI images of radiofrequency lesions from clinically by guest on May 12, 2018 http://circep.ahajournals.org/ Downloaded from relevant ablation target regions in both the right and the left atria ( Figure 4).…”

“…69 This method has recently been adapted to an integrated intracardiac mapping and ultrasound imaging system. 70 An ARFI image is created by delivering a series of ultrasound pulses to mechanically displace tissue, measuring the displacement of each image pixel in response to the push pulse using standard ultrasound techniques, and then displaying high-resolution displacement information superimposed on the ultrasound image. Regions of tissue within the imaged field that are stiff demonstrate smaller displacements than more elastic tissue.…”

Imaging for cardiac electrophysiology

“…puncture to access the LA from the right atrium (RA), visualise the pulmonary vein ostia, visualise the oesophagus to avoid collateral damage, and helps to recognise complications such as perforations. ICE with acoustic radiation force imaging 3 can assess tissue elasticity and directly visualise ablation lesions, which are stiffer than normal portions of the LA, and can potentially identify gaps.…”

Real-time atrial wall imaging during radiofrequency ablation in a porcine model

“…Several attempts have been made to provide additional information on functional and morphological RF-induced changes [11][12][13][14][15][16] . Photoacoustic imaging has been used in vitro with encouraging results 13 .…”

“…Magnetic resonance imaging (MRI) is limited by spatial resolution and the need of MRI-compatible equipment 15 . Optical coherence tomography (OCT) is limited by depth resolution 16 , and acoustic radiation-force impluse (ARFI) is still limited in vivo by motion artifacts 12 . One study used a laboratory-made M-mode catheter 11 , and we found no report of the use of clinically available catheters and twodimensional (2D) echographic imaging.…”