NONINVASIVE MYOCARDIUM ACTIVATION MAPPING BASED ON NUMERICAL RECONSTRUCTION OF BIPOLAR ELECTROGRAMS
Presently, methods of noninvasive imaging of electrophysiological activity in the heart - ECGI (Electrocardiographic Imaging) - are being developed, based on the solution of the inverse ECG problem, i.e. estimation of electrical potential on the epicardial heart surface on hand of body surface mapping (BSM) that samples electrical activity with high spatial resolution over an extensive thoracic surface. Myocardium activation sequence - activation mapping - is one of the main goals of the heart Electrophysiological (EP) study. To construct activation maps on hand of a set of unipolar electrograms received by solving the inverse ECG problem, the approach is mainly used, whereby the excitation wave arrival time to a definite myocardium location is estimated by the so called time of internal deflection (TID) of the unipolar Electrogram (EG). But the method adopted from the praxis of catheter EP study does not always give satisfactory results. Therefore, search for more effective activation mapping method is a topical task of the noninvasive Electrocardiography. We present a method of activation mapping comprising two stages: reconstruction of the vector field of myocardium excitation direction and subsequent construction of isochrones maps. In this method, the myocardium excitation direction is determined by analysing the bipolar Electrograms, reconstructed on the basis of BSM data. The direction is chosen in accordance with the modelling results as the axis direction of the bipolar lead with the maximal signal amplitude and symmetry. To verify the method of noninvasive activation mapping, 56 patients were investigated during years 2010-2011 at Bakoulev Scientific Centre for Cardiovascular Surgery of Russian Academy of Medical Sciences, Department for Tachyarrhythmia Surgical Treatment. The patients were characterized by: WPW syndrome - 18, atrial ectopic extrasystoles - 12, ventricular ectopic extrasystoles - 26. All patients underwent noninvasive activation mapping, invasive EP study afterwards, also with the aid of CARTO system, and catheter high frequency ablation (HFA). Noninvasive activation mapping has been performed with the aid of the “Amycard” diagnostic system. Additionally to options described elsewhere, the system enables for simultaneous epicardial and endocardial mapping. In all cases the noninvasive isochrones maps correspond to awaited course of myocardium excitation and satisfactory well coincide with CARTO endocardial isochrones maps. Noninvasive isochrones maps defined by reconstruction of the myocardium excitation directions have high spatial resolution: regions of early activation on those maps well coincide with localization of ectopic foci and zones of pre-excitation. Accordingly, the regions of early activation are much narrower than the appropriate zones on maps defined by internal deflection time of unipolar electrograms.