Figure 1: Panel A shows the 12-lead ECG intrinsic LBBB with QRS duration of 196ms (the precordial leads were placed on the right side due to dextroposition of the heart chambers); Panel B shows the 12-lead ECG after His-CRT with QRS duration of 146ms and correction of the LBBB; Panel C shows the cardiac CT scan demonstrating the ‘Scimitar’ vein – anomalous drainage of the right pulmonary vein into the IVC. RA = right atrium, RV = right ventricle, LV = left ventricle, PA = pulmonary artery, IVC = inferior vena cava, SV = Scimitar vein.
Figure 2: Panel A shows the CARTOSEG™ modality wherein the Cardiac CT was integrated onto the CARTO™ electro-anatomical mapping system. Note the perpendicular orientation of the interventricular septum at RAO 20; Panels B and C show the geometries created by an electrophysiology catheter which was integrated with the cardiac CT scan. His bundle (yellow marker) was tagged (white arrow). Panel D and E show the intracardiac electrograms observed with the lead. The distal H-V was 58ms. Pacing at this site resulted in correction of the LBBB; AP = antero-posterior, RAO = right anterior oblique, LAO = left anterior oblique, TA = tricuspid annulus, CS = coronary sinus, RA = right atrium, RAA = right atrial appendage, RV = right ventricle, RVOT = right ventricular outflow tract, LV = left ventricle, PA = pulmonary artery, IVC = inferior vena cava.