Effect of epicardial fat on electroanatomical mapping and epicardial catheter ablation

The purpose of this study was to correlate 3-dimensional distribution of epicardial fat on computed tomography (CT) with electroanatomical (EA) voltage maps obtained during percutaneous epicardial mapping in order to determine the fat thickness cut-off that results in voltage attenuation and to establish normal ventricular epicardial voltage criteria in the absence of fat.

Epicardial fat can mimic scar tissue when epicardial voltage mapping is performed, as both result in low epicardial voltage. Cardiac CT can differentiate epicardial fat from scar or muscle on the basis of their distinct attenuations.

Transcutaneous epicardial mapping was performed in a consecutive series of 14 patients. A cardiac CT was performed before the procedure and a 3-dimensional image of the epicardial fat was generated and registered with the epicardial EA voltage map.

In patients without cardiomyopathy (n = 8), a voltage ≥1.5 mV best correlated with the absence of epicardial fat. A fat thickness ≥2.8 mm resulted in voltage attenuation and best separated low voltage (<1.5 mV) from normal voltage (≥1.5 mV; sensitivity 81%, specificity 81%, area under the curve 0.85). In patients without cardiomyopathy, the low-voltage area matched well with the area of epicardial fat. In the 6 patients with nonischemic cardiomyopathy, the low-voltage area by far exceeded the area accounted for by epicardial fat; this corresponded with the presence of scar tissue. Epicardial ablations at sites with >10 mm of fat were ineffective.

Cardiac CT identifies epicardial fat that can mimic scar tissue during epicardial EA voltage mapping, which is important during epicardial mapping and ablation.