New insight into scar-related ventricular tachycardia circuits in ischemic cardiomyopathy: Fat deposition after myocardial infarction on computed tomography--A pilot study

Abstract

Background Myocardial fat deposition (FAT-DEP) has been frequently observed in regions of chronic myocardial infarction in patients with ischemic cardiomyopathy (ICM). The role of FAT-DEP within scar-related ventricular tachycardia (VT) circuits has not been investigated. Objective This pilot study aimed to assess the impact of myocardial FAT-DEP on local electrograms and VT circuits in patients with ICM. Methods Contrast-enhanced computed tomography (CE-CT) was performed in 22 patients with ischemic VT. Electroanatomic map (EAM) points were registered to corresponding CE-CT images. Myocardial FAT-DEP were identified and characterized using a post-processing image overlay that highlighted areas below 0 Hounsfield units (HU). The mean attenuation of local myocardial regions corresponding to sampled electrograms was measured on short axis images. The associations of mean attenuation with bipolar and unipolar amplitudes, left ventricular (LV) wall thickness and VT circuit sites were investigated. Results Of 1801 EAM points, 519 (28.8%) were located in regions with FAT-DEP. Significant differences were observed in mean intensity (23.2±35.6 vs. 81.7±21.9 HU, P<0.001), bipolar (0.75±0.83 vs 2.9±2.4 mV, P<0.001) and unipolar (3.1±1.7 vs. 7.4±4.3 mV, P<0.001) amplitudes and LV wall thickness (5.2±1.7 vs. 8.2±2.5 mm, P<0.001) between regions with and without FAT-DEP. Lower HU was strongly associated with lower bipolar and unipolar amplitude (P<0.0001, respectively). Importantly, FAT-DEP was associated with critical VT circuit sites with fractionated or isolated potentials. Conclusions FAT-DEP was associated with electrogram features and VT circuit sites. Further work will be needed to determine whether FAT-DEP plays a causal role in the generation of ischemic scar-related VT circuits.

Role of adipose tissue in the pathogenesis of cardiac arrhythmias

“…In the non-inducible group, significance was not achieved for any histological criteria. In a pilot study involving 22 patients with ischemic VT the presence of lipomatous metaplasia was strongly associated with lower bipolar and unipolar amplitudes 7 . In addition to this LM was associated with critical VT circuits with fractionated and isolated potentials.…”

“…In inherited aetiologies like ARVC 4 and myotonic dystrophy 5 , fibro-fatty infiltration of the myocardium is associated with lethal ventricular arrhythmias. Recently in the both the animal model of chronic myocardial infarction and humans the presence of intramyocardial adipose tissue has been associated with altered ventricular electrophysiology 6,7 . In this article we review the overall role of cardiac adipose tissue in normal conditions and in the genesis of cardiac arrhythmias.…”

Can Fat Deposition After Myocardial Infarction Alter the Performance of RF Catheter Ablation of Scar‐Related Ventricular Tachycardia?: Results from a Computer Modeling Study

“…A: Histological image showing the constituent tissues in a scar within the ventricular wall: viable myocardium, fibrous tissue, and fat (reproduced from Sasaki et al . with permission from Elsevier).…”

“…We created computer models of human ventricular tissue (wall thickness: 7 mm) with associated epicardial fat (2 mm thick) and connective tissue. The ventricular wall comprised 3 tissue types—viable myocardium, fibrous tissue, and fat—following a spatial distribution based on a microscopic image reported by Sasaki et al . (see Fig.…”

“…Yet, experimental studies suggest that the presence of scar by itself does not significantly impact lesion size or intramural temperatures reached in the cardiac tissue during RF ablation . However, in these studies RF ablation was performed 1−4 months after creating the infarct model, not taking into account the impact of fat deposition that is typically encountered much later in regions of chronic myocardial infarction coexisting with areas of fibrosis that together form the underlying substrate for reentrant VT . The presence of fat as a component of the underlying substrate for scar‐mediated VT is indeed relevant since this entity can seriously impede the passage of RF current due to its low electrical conductivity .…”