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

Heart Rhythm. 2015 Jul;12(7):1508-18. doi: 10.1016/j.hrthm.2015.03.041. Epub 2015 Mar 23.

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.

Keywords: Computed tomography; Fat; Ischemic cardiomyopathy; Magnetic resonance imaging; Ventricular tachycardia.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adipose Tissue / diagnostic imaging*
  • Aged
  • Body Surface Potential Mapping / methods
  • Cardiomyopathies* / complications
  • Cardiomyopathies* / diagnosis
  • Cardiomyopathies* / etiology
  • Cardiomyopathies* / physiopathology
  • Cicatrix* / etiology
  • Cicatrix* / pathology
  • Contrast Media / pharmacology
  • Female
  • Humans
  • Imaging, Three-Dimensional / methods
  • Magnetic Resonance Imaging / methods
  • Male
  • Middle Aged
  • Myocardial Infarction / complications*
  • Myocardium / pathology*
  • Radiographic Image Enhancement
  • Reproducibility of Results
  • Tachycardia, Ventricular* / diagnosis
  • Tachycardia, Ventricular* / etiology
  • Tachycardia, Ventricular* / physiopathology
  • Tomography, X-Ray Computed / methods

Substances

  • Contrast Media