## 3 Results
### Testing Data
#### 3.2.2 Cardiac Resynchronization Therapy Simulations  
In the three analyzed testing cases, the optimal configuration consisted in leads located in the RV apex and the basal LV (\(RV_{apx}-LV_{bus}\) configuration), providing the best recovery metric values and overall cardiac resynchronization. The CRT leads were activated at practically the same time in the three testing cases, with a time interval under 0.5 ms between them. The RV was typically triggered prior to the LV (see histograms in Figure 6 for the infarcted testing case), where it was always located the last activation point. Figure 6 shows the local activation time maps for a an infarcted case (Fig 6) of the testing database in CRT condition, provided by the EAM, and for different simulated lead configurations. Furthermore, histograms of the percentage of electrically activated heart tissue for the right and left epicardial layers are displayed to better represent inter-ventricular delays with different lead configurations. It can be easily appreciated the better inter-ventricular synchronization provided by the \(RV_{apx}-LV_{bus}\) lead configuration when analyzing the histograms, which was also confirmed by a low TAT and recovery discrepancy between the SPH-based simulation and EAM data, as shown in Table 3. We can also see in Figure 6 the impact of changing the LV lead from the basal (or latest activated point) to the apex, increasing the inter-ventricular delay compared to the remaining configurations. Additionally, placing the RV lead in the RVOT was better than in the earliest activated point (i.e., lateral wall), as can be seen in Figure 6 (fourth and fifth row, respectively), the former having less IVD. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline  & \multicolumn{3}{c}{**Pig 4**} & \multicolumn{3}{c}{**Pig 5**} & \multicolumn{3}{c}{**Pig 6 (*)**} \\  & \multicolumn{2}{c}{**EAM**} & \multicolumn{2}{c}{**SPH-Sim**} & \multicolumn{2}{c}{**EAM**} & \multicolumn{2}{c}{**SPH-Sim**} & \multicolumn{2}{c}{**EAM**} & \multicolumn{2}{c}{**SPH-Sim**} \\ \cline{2-13}  & LBBB & CRT & LBBB & CRT (\(RV_{apx}-LV_{bus}\)) & LBBB & CRT & LBBB & CRT (\(RV_{apx}-LV_{bus}\)) & LBBB & CRT & LBBB & CRT (\(RV_{apx}-LV_{bus}\)) \\ \cline{2-13} TAT (ms) & 61 & 59 & 56 & 36.8 & 92 & 70 & 76 & 55 & 67 & 49 & 73.7 & 47 \\ \hline LAT RMSE (ms) & & & 5.1 & 13.2 & & & 8.2 & 14.6 & & 5.9 & 10.7 \\ \hline IVD (ms) & 19.61 & \(-\)9.04 & 14.7 & 0.5 & 25.58 & 7.83 & 21.5 & 1.2 & 12.75 & 2.63 & 18.3 & 0.8 \\ \hline LV-TD (ms) & 16.55 & \(-\)12.95 & 5.8 & \(-\)0.7 & 32.68 & \(-\)8.45 & 9.8 & -0.3 & 14.22 & \(-\)1.97 & 6.8 & 0.6 \\ \hline Recovery (\%) & 17.95 & & & 100.84 & 46.09 & & 68.2 & 637 & & 666 \\ \hline \end{tabular}
\end{table} 
Table 3: Metrics characterizing the electrical activation maps in testing cases from measurements and meshless simulations, including the best lead configuration in the cardiac resynchronization therapy scenario. EAM: electroanatomical maps. SPH-Sim: Simulation with smoothed particle hydrodynamics meshless method. LBBB: left bundle branch block. CRT: cardiac resynchronization therapy. TAT: total activation time. LAT-RMSE: local activation time root mean square error. IVD: inter-ventricular delay. LV-TD: left ventricle transmural delay. \(RV_{apx}-LV_{bus}\): CRT leads in the right ventricular apex and basal left ventricle. (*) indicates an infarcted pig. The non-infarcted cases of the testing database (Fig 4 and Fig 5) had an identical overall behavior with respect to optimal lead configuration. However, they presented large TAT errors between SPH-based simulations and EAM data (22.2 ms and 15 ms for Pig 4 and Pig 5, respectively), with CRT simulations providing lower TAT values and, consequently, larger recovery than EAM data (see Table 3). The difference between optimal SPH-based simulations and EAM measurements was due to a different lead location.