Correlation of Scar in Cardiac MRI and High‐Resolution Contact Mapping of Left Ventricle in a Chronic Infarct Model

Abstract

BackgroundEndocardial mapping for scars and abnormal electrograms forms the most essential component of ventricular tachycardia ablation. The utility of ultra‐high resolution mapping of ventricular scar was assessed using a multielectrode contact mapping system in a chronic canine infarct model.MethodsChronic infarcts were created in five anesthetized dogs by ligating the left anterior descending coronary artery. Late gadolinium‐enhanced magnetic resonance imaging (LGE MRI) was obtained 4.9 ± 0.9 months after infarction, with three‐dimensional (3D) gadolinium enhancement signal intensity maps at 1‐mm and 5‐mm depths from the endocardium. Ultra‐high resolution electroanatomical maps were created using a novel mapping system (Rhythmia Mapping System, Rhythmia Medical/Boston Scientific, Marlborough, MA, USA) Rhythmia Medical, Boston Scientific, Marlborough, MA, USA with an 8.5F catheter with mini‐basket electrode array (64 tiny electrodes, 2.5‐mm spacing, center‐to‐center).ResultsThe maps contained 7,754 ± 1,960 electrograms per animal with a mean resolution of 2.8 ± 0.6 mm. Low bipolar voltage (<2 mV) correlated closely with scar on the LGE MRI and the 3D signal intensity map (1‐mm depth). The scar areas between the MRI signal intensity map and electroanatomic map matched at 87.7% of sites. Bipolar and unipolar voltages, compared in 592 electrograms from four MRI‐defined scar types (endocardial scar, epicardial scar, mottled transmural scar, and dense transmural scar) as well as normal tissue, were significantly different. A unipolar voltage of <13 mV correlated with transmural extension of scar in MRI. Electrograms exhibiting isolated late potentials (ILPs) were manually annotated and ILP maps were created showing ILP location and timing. ILPs were identified in 203 ± 159 electrograms per dog (within low‐voltage areas) and ILP maps showed gradation in timing of ILPs at different locations in the scar.ConclusionsUltra‐high resolution contact electroanatomical mapping accurately localizes ventricular scar and abnormal myocardial tissue in this chronic canine infarct model. The high fidelity electrograms provided clear identification of the very low amplitude ILPs within the scar tissue and has the potential to quickly identify targets for ablation.

First clinical experience using a novel high-resolution electroanatomical mapping system for left atrial ablation procedures

“…Our data demonstrate that Rhythmia in conjunction with the minibasket catheter can reliably visualize PVI, detect gaps after WACA, and visualize electrical propagation of atrial macroreentrant tachycardia, corroborating previous results from animal and human studies [7,9,10,16].…”

Selection of Critical Isthmus in Scar-Related Atrial Tachycardia Using a New Automated Ultrahigh Resolution Mapping System

“…2 In a ventricular scar animal model, scar detected by the Rhythmia system using the basket for mapping correlated best with the magnetic resonance imaging. 5 We may consider that patients included in this series had extensive atrial scarring. Indeed, 58±25% of the LA surface was <0.5 mV.…”

The Future of Arrhythmias and Electrophysiology

“…More recently, an appreciation of the need to improve recording quality to achieve detection of very low amplitude signals, particularly to guide ablation of scar related arrhythmias and some idiopathic arrhythmias, has begun to receive appropriate attention. 18, 19 Better mapping catheters and recording equipment with refined signal processing will facilitate definition of arrhythmias and further improve our understanding of pathophysiology and ability to target ablation.…”

“…The concept of directing ablation to anatomic substrate defined from noninvasive imaging has been demonstrated and will become a reality as imaging resolution improves. 18, 24 CT imaging which has better spatial resolution but is perhaps more limited in distinguishing fibrous scar from myocytes, and ultrasound imaging, also presently limited in the ability to define the fine structure of scars, is none the less showing promise. 25, 26 The use of nuclear pharmaceuticals to assess abnormal innervation in the arrhythmogenic area may also provide further insights into arrhythmogenesis and its prevention.…”