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

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

Takeshi Sasaki  1 , Hugh Calkins  2 , Christopher F Miller  2 , Menekhem M Zviman  2 , Vadim Zipunnikov  3 , Tomio Arai  4 , Motoji Sawabe  5 , Masashiro Terashima  6 , Joseph E Marine  2 , Ronald D Berger  2 , Saman Nazarian  2 , Stefan L Zimmerman  7
Affiliations

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

Takeshi Sasaki et al. Heart Rhythm. 2015 Jul.

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.

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Conflict of interest statement

Conflict of Interest Disclosures – The Johns Hopkins University Conflict of Interest Committee manages all commercial arrangements.

Figures

Figure 1
Figure 1. Methods
(A) In the left-side panels, Fat depositions (FAT-DEP) identified as low attenuation regions on contrast enhanced computed tomography (CE-CT) are indicated by red arrows (left panels) in 2 different patients with ischemic cardiomyopathy. FAT-DEPs on CE-CT are also highlighted by a red mask based upon intensity measurements (CT values from −180 to 0 Hounsfield units). Late gadolinium-enhanced cardiac magnetic resonance (LGE-CMR) shows enhancement in the corresponding plane to CE-CT. (B) Electrogram (EGM) parameters and potential types were assessed. (C) Electroanatomic Map (EAM) points were superimposed onto the corresponding short axis CE-CT images divided into 20 radial sectors.
Figure 2
Figure 2. Fat Depositions in Ischemic Scar-related VTs
Pie graph demonstrating the distribution of sectors with FAT-DEP, without FAT-DEP, calcification, and lead artifact. Abbreviations as in Figure 1.
Figure 3
Figure 3. Comparison of Electrogram Characteristics between the Sectors with and without FAT-DEP
electrogram parameters between the CE-CT sectors with and without FAT-DEP were compared with boxplot graphs demonstrating the median (white line), interquartile range (solid box), range (black line), and outliers. Abbreviations as in Figure 1.
Figure 4
Figure 4. CT Intensity in Regions with Low Voltage Area on EAM and Scar on LGE-CMR
The mean CT intensities in normal myocardium with >1.5mV bipolar voltage on electroanatomic map (EAM) and no scar on LGE-CMR were 86.1±21.1 HU and, 80.3±17.0 HU, respectively. In addition, the mean intensities in transmural scar with 0.5mV> bipolar voltage and >75% scar transmurality were 20.7±36.9 HU and 21.9±12.2 HU, respectively. HU=Hounsfield unit, LGE-CMR=late gadolinium enhanced cardiac magnetic resonance
Figure 5
Figure 5. Association of Fat Depositions with VT Circuit Sites
The figure summarizes electrogram characteristics of 32 VT circuit sites among sites stratified by the absence of fat depositions (FAT-DEP), being on the border of FAT-DEP, or within regions of FAT-DEP.
Figure 6
Figure 6. VT Circuit Sites within the Area with Fat Depositions in a Case with inferior myocardial Infarction
(A) Bipolar voltage map shows large low voltage area in regions with inferior myocardial infarction. (B) The segmented FAT-DEP on EAM looks very similar to the bipolar voltage map and the segmented scar on LGE-CMR. (C, D) A critical VT circuit site with 12/12 pace match and a concealed entrainment was identified within FAT-DEP. (E) FAT-DEP on CE-CT and (F) scar on LGE-CMR was identified in the same area with myocardial infarction.
Figure 7
Figure 7. Histology of Fat Depositions in a Case with Anteroseptal Myocardial Infarction
Fat depositions within myocardium in the left ventricle (LV) were observed (A) macroscopically and (B) microscopically in a patient with anteroseptal myocardial infarction.
See this image and copyright information in PMC

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