[Noninvasive Electrophysiological Mapping in Patients With Complete Left Bundle Branch Block and Different Modes of...

to investigate possibilities of noninvasive electrophysiological mapping (NEM) during biventricular (BiV) pacing and to compare the results with data of 12 lead ECG and tissue Doppler echocardiography (TDI).

The study included 25 patients with complete left bundle branch block (LBBB) and implanted cardiac resynchronization therapy (CRT) system. Twenty-two patients were CRT responders, three other patients did not demonstrate a clear effect. NEM was performed with "Amycard 01C EP LAB" system and multi slice computed tomography.

Qualitative analysis of isochronous maps at NEM showed that the most homogenous color coding of the left ventricle (LV) may correspond to the optimal BiV pacing mode. A statistically significant positive correlation between the width of the QRS complex during a set BiV pacing mode and the standard activation deviation time, measured at NEM, for 12 segments (SD12) LV (r= 0,88, p<0,0001) was observed. With the minimum value of SD12 and biventricular QRS width at the same time, three patients had intraventricular dyssynchrony. A comparative analysis of NEM and TDI methods in terms of interventricular dyssynchrony (IVD) at LBBB revealed statistically significant positive correlation (r=0,58, p=0,005).

These data show that both minimal values of QRS and SD12 at BiV pacing are not accompanied by the effect of CRT in all patients. The lack of response from this type of therapy is associated with a non-optimal position of the LV electrode. Qualitative assessment of isochronous maps at NEM demonstrates intraventricular dyssynchrony and can help in selecting the optimal mode of BiV pacing.