Abstract
BACKGROUND: Myocardial fat deposition (FAT-DEP) has been frequently observed in regions of chronic myocardial infarction in patients with ischemic cardiomyopathy. 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 ischemic cardiomyopathy. METHODS: Contrast-enhanced computed tomography was performed in 22 patients with ischemic VT. Electroanatomic map points were registered to the corresponding contrast-enhanced computed tomography images. Myocardial FAT-DEP was identified and characterized using a postprocessing 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 wall thickness, and VT circuit sites were investigated. RESULTS: Of 1801 electroanatomic map points, 519 (28.8%) were located in regions with FAT-DEP. Significant differences were observed in mean intensity (23.2 ± 35.6 HU vs 81.7 ± 21.9 HU; P < .001), bipolar (0.75 ± 0.83 mV vs 2.9 ± 2.4 mV; P < .001) and unipolar (3.1 ± 1.7 mV vs 7.4 ± 4.3 mV; P < .001) amplitudes, and left ventricular wall thickness (5.2 ± 1.7 mm vs 8.2 ± 2.5 mm; P < .001) between regions with and without FAT-DEP. Lower HU was strongly associated with lower bipolar and unipolar amplitudes (P < .0001, respectively). Importantly, FAT-DEP was associated with critical VT circuit sites with fractionated or isolated potentials. CONCLUSION: FAT-DEP was associated with electrogram characteristics 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.