Magnetocardiographic study of patients with right and left bundle branch blocks

It has been recently proposed that magnetocardiographic mapping (MCG) can be useful for early diagnosis of IHD also in patients with LBBB; however, MCG patterns of cBBB in the absence of IHD have not so far extensively investigated. This study was aimed to define typical magnetic field distribution (MFD) patterns and several quantitative parameters of ventricular depolarization (QRS) and repolarization (VR), in patients with cBBB. 38 patients (pts) with cBBB at the ECG [15 RBBB, 19 LBBB, 4 RBBB+LAH] and 33 healthy subjects (HS) were consecutively investigated with an unshielded 36-channels DC SQUID MCG system (sensitivity is 20 fT/Hza1/2, above 1 Hz). Quantitative analysis of MFD maps was automatically performed during the QRS and VR intervals. In RBBB pts, the direction of septal depolarization was normal. A significant ( pb0.001) difference of Rpeak effective magnetic dipole orientation (EMDo) was observed between RBBB pts with (52.8°±15) and without (−50.8°±28.5) cardiac abnormalities (CaAb), or associated with LAH (−148°±17.3). In pts with RBBB+LAH, average ST and Tpeak EMDo values were different ( pb0.01 and pb0.05, respectively) from those of pts with RBBB only. 8 pts with LBBB had dilated cardiomyopathy (DCM), 3 had IHD. As compared to HS, LBBB was characterized by inverted (from right-to-left) direction of septal activation, counterclockwise rotation of Rpeak EMDo (−113.4°±7.6) and an inversion of ST and Tpeak EMDo (61.4°±14.1 and 57.9°±14.1, respectively). In the 3 IHD pts, T-wave parameters were not significantly different from those with non-ischemic 22 LBBB. In one post-myocarditis DCM, ST and Tpeak EMDo rotated clockwise, toward more positive 23 values. MCG differentiates RBBB associated with CaAb from those without CaAb. MCG criteria to 24 detect ischemia in LBBB pts are not defined yet.