A Confounding Duo: Fat-Induced Disturbance of Low-Voltage Detection in Epicardial 3D Electroanatomical Mapping During Sinus and Ventricular-Paced Rhythm

Introduction: In patients with scar-related ventricular tachycardia, ultra-high-density multipolar catheters and 3D electroanatomical mapping are frequently used for ablation guidance. However, the impact of pacing-induced changes in activation vectors on voltage map accuracy and its interplay with the confounding epicardial fat tissue remains unclear.

Methods and Results: In healthy domestic pigs, we localized epicardial fat deposits using ECG-triggered, contrast-enhanced computed tomography and assessed their influence on 3D electroanatomical (EAM) epicardial high-density voltage and activation maps (>4000 points per heart) which were acquired on the same day. The EAMs were recorded in sinus and ventricular-paced rhythm during intubation narcosis using a 20-polar star-shaped catheter with a cardiac tissue proximity filter based on catheter location and impedance measurements. Ventricular pacing was performed at 120 bpm using a permanent pacemaker electrode placed in the right ventricular septum.

The CT scans showed a characteristic distribution of epicardial fat, predominantly located in the atrioventricular and interventricular sulci. As illustrated in Figure 1, one of the most prominent deposits of epicardial fat is found in the anterior interventricular sulcus (AIS), which surrounds the left anterior descending artery and provides cushioning between the heart and the sternum.

All EAMs in sinus and paced rhythm identified low-voltage areas (defined < 0.5 mV) from the basal to apical anterior wall corresponding to the AIS and the posterior wall's atrioventricular region. The extent of low voltage varied significantly between the sinus and the paced maps (p < 0.001, η² = 0.107–0.313). To evaluate the influence of epicardial fat, we analyzed the voltage heterogeneity of affected regions. For this purpose, all EAMs were segmented into 2 mm × 2 mm blocks, with the mean voltage calculated for each section. Low voltage was defined as <0.5 mV, while normal voltage was categorized as ≥1.5 mV. To evaluate mapping heterogeneity around the AIS, we compared the voltages of ten blocks along a midline representing the interventricular septum in both septal and lateral directions (Figure 2).

 

Comparisons of sinus and paced rhythm maps by blocks and columns revealed significant voltage heterogeneity across all maps (p < 0.001; n ≥ 1500 samples per condition from 2 hearts). In paced rhythm, voltage disparity was significantly increased as compared to sinus rhythm (Table 1).

 

Conclusion: Epicardial fat tissue contributes to low voltage regions in epicardial electroanatomical voltage maps. However, annotation accuracy decreases further when maps are obtained during right ventricular pacing compared to sinus rhythm.