Detection of incomplete left bundle branch block by non-invasive electrocardiographic imaging

This study sought to compare noninvasive ECGi with local epicardial activation time mapping to detect subtle electrical dyssynchrony between the left and right ventricles. We used an ex-vivo porcine model of complete and incomplete left bundle branch block (LBBB) in an experimental torso-tank. LBBB was induced in Langendorff-perfused pig hearts suspended in tank shaped as a male torso fitted with 256 body surface electrodes and 108 epicardial electrodes. Epicardial and surface potentials were recorded during sinus rhythm and ventricular pacing. Post-experiment MRI provided the epicardial geometry and electrode (epicardial and surface) locations. Epicardial electrograms were calculated and the derived reconstructed values for electrical dyssynchrony were compared to those recorded. LBBB with varying levels of electrical delay was successfully induced in 7 out of 8 hearts, with incomplete LBBB present in 4. ECGi correctly identified the presence/absence of dyssynchronous activity in 7 of the 8 cases, including incomplete LBBB with very subtle delay (VEU = 17 ms, TAT = 45 ms). Overall, there was no significant difference between measured and calculated VEU (p=0.06), or TAT values (p=0.21).