Cardiac Lesion Mapping <italic>In Vivo</italic> Using Intracardiac Myocardial Elastography

Abstract

Radio frequency (RF) ablation of the myocardium is used to treat various cardiac arrhythmias. The size, spacing, and transmurality of lesions have been shown to affect the success of the ablation procedure; however, there is currently no method to directly image the size and formation of ablation lesions in real time. Intracardiac myocardial elastography (ME) has been previously used to image the decrease in cardiac strain during systole in the ablated region as a result of the lesion formation. However, the feasibility of imaging multiple lesions and identifying the presence of gaps between lesions has not yet been investigated. In this paper, RF ablation lesions ( ) were generated in the left ventricular epicardium in three anesthetized canines. Two sets of two lesions each were created in close proximity to one another with small gaps (1.5 and 4 cm), while one set of two lesions was created directly next to each other with no gap. A clinical intracardiac echocardiography system was programmed to transmit a custom diverging beam sequence at 600 Hz and used to image the ablation site before and after the induction of ablation lesions. Cumulative strains were estimated over systole using a normalized cross-correlational displacement algorithm and a least-squares strain kernel. Afterward, lesions were excised and subjected to tetrazolium chloride staining. Results indicate that intracardiac ME was capable of imaging the reduction in systolic strain associated with the formation of an ablation lesion. Furthermore, lesion sets containing gaps were able to be distinguished from lesion sets created with no gaps. These results indicate that the end-systolic strain measured using intracardiac ME may be used to image the formation of lesions induced during an RF ablation procedure, in order to provide critical assessment of lesion viability during the interventional procedure.

Monitoring Canine Myocardial Infarction Formation and Recovery via Transthoracic Cardiac Strain Imaging

“…Although ME does not explicitly measure elastic properties of the myocardium, the strain imaging technique is based on the signal processing approach detailed in the first publication defining elastography (Ophir et al 1991). Previous applications have included ablation monitoring in canines and humans (Bunting et al 2018;Grondin et al 2015), tracking the progression of acute ischemia in an open-chest canine model (Lee et al 2011), and imaging suspected coronary artery disease (CAD) patients (Grondin et al 2017). ME has also been used to image MI in a murine model (Luo et al 2007).…”

Robust, high-density lesion mapping in the left atrium with near-infrared spectroscopy

“…Magnetic resonance imaging and computed tomography have both been explored for this purpose, but these approaches are costly and difficult to integrate with real-time feedback 12 – 16 Various ultrasound-based methods have also shown promise in monitoring cardiac ablation but are still in the development 17 , 18 . Recently, optical imaging techniques have been applied to the challenge of RFA lesion characterization.…”

A comparison between unfocused and focused transmit strategies in cardiac strain imaging

“…Strain imaging has proven to be a useful tool in assessing myocardial health (D'hooge et al 2000, Abraham et al 2007, Dandel et al 2009, Smiseth et al 2016. Myocardial Elastography (Konofagou et al 2002, Lee et al 2007, a cardiac strain imaging technique developed by our group, is the particular focus of this study; its applications include tracking ischemia progression in canines (Lee et al 2011), lesion monitoring during RF ablation in canines and humans (Grondin et al 2015, Bunting et al 2018, and quantitatively differentiating ischemic from normal patients as validated by nuclear imaging and angiography (Grondin et al 2017b).…”