The patient underwent Non-invasive EPI of the heart. A typical extrasystolic ventricular complex was selected for calculation. Isopotential maps revealed a stable region of negative potential spreading concentrically in the anterior septum of the excretory tract of the right ventricle; that proves the presence of ectopic factor in the given zone.
Activation break on the endocardial surface appeared at the 264th millisecond from the beginning of the analyzed ECG fragment, break on the epicardial surface appeared at the 268th millisecond. Advance of endocardial activation is 4 milliseconds. Taking into account a small (3 mm) thickness of myocardium in this zone, this advance indicates subendocardial location of ectopic focus.
These maps show sequence of myocardium activation at the beginning of myocardium activation. However, activation maps in the FND mode do not allow tracking the dynamics of ventricular activation during the entire period of depolarization. To visualize the full sequence of myocardium activation, activation mapping in the ADM mode was used.
Vector field of myocardium activation directions revealed typical effect of divergence of vector from the regions of endocardial and epicardial activation breaks.
According to data of isochronous maps and activation spread maps, activation appeared in the endocardial surface of the anterior-lateral wall of excretory tract of the right ventricle and ended in the posterior walls and in the apical regions of the right and left ventricles. The advance of endocardial activation break in the region of early activation is also 4 milliseconds.
Additionally, isochronous maps according to the TID method were built in the "advanced" mode.
Isochronous map according to the TID method reveals the same sequence of ventricular activation compared to the AMD method. However, isochronous map according to the TID method has much lower spatial resolution (Fig. 12).
Thus, according to data of Non-invasive activation mapping using different research methods of myocardium activation it is established that the reason for premature heartbeats is an ectopic source located subendocardially in the anterior-septum wall of excretory tract of the right ventricle. Position of the ectopic focus is highlighted with the markers on the voxel model of the heart (Fig. 13). Invasive EPI confirmed the determined location of ectopic focus. The patient underwent effective RFA.