Cardiac Electrical Dyssynchrony is Accurately Detected by Noninvasive Electrocardiographic Imaging

Poor identification of electrical dyssynchrony is postulated to be a major factor contributing to the low success rate for cardiac resynchronization therapy (CRT). To evaluate body surface mapping and electrocardiographic imaging (ECGi) to detect electrical dyssynchrony noninvasively. Langendorff-perfused pig hearts (n=11) were suspended in a human torso-shaped tank, with LBBB induced through ablation. Recordings were taken simultaneously from a 108-electrode epicardial sock and 128 electrodes embedded in the tank surface during sinus rhythm and ventricular pacing. CT provided electrode and heart positions in the tank. Epicardial unipolar electrograms were reconstructed from torso potentials using ECGi. Dyssynchrony markers from torso potentials (e.g. QRS-duration) or ECGi (total activation time (TAT), interventricular delay (D-LR) and intraventricular markers) were correlated with those recorded from the sock. LBBB was induced (n=8) and sock-derived activation maps demonstrated interventricular dyssynchrony (D-LR and TAT) in all cases (p <0.05), and intraventricular dyssynchrony for complete LBBB (p <0.05) compared to normal. Only D-LR returned to normal with biventricular pacing (p=0.1). Torso markers increased with large degrees of dyssynchrony, and no reduction was seen during biventricular pacing (p>0.05). Although ECGi markers were significantly lower than recorded (p <0.05) there was a significant strong linear relationship between ECGi and recorded values. ECGi correctly diagnosed electrical dyssynchrony, and interventricular resynchronization in all cases. The latest site of activation was identified to 9.1±0.6 mm by ECGi. ECGi reliably and accurately detects electrical dyssynchrony, resynchronization by biventricular pacing, and the site of latest activation, providing more information than body surface potentials