Background: Inverse electrocardiography (iECG) is used to non-invasively estimate the cardiac activation sequence. This becomes increasingly difficult during His-Purkinje mediated ventricular activation when the myocardium is activated through multiple activation wavefronts. Equivalent dipole layer based iECG requires an initial estimate of the ventricular activation sequence, wherein cardiac physiology can be incorporated. A physiologically realistic initial estimation should be based on a combination of waveforms initiated at His-Purkinje associated endocardial locations, instead of an iterative multi-focal search. In this study, performance of multi-focal iECG and multi-wave iECG was compared.
Methods: Six subject specific CT-based geometries of ventricles, lungs and thorax were created and supplemented with electrode positions. In ventricular geometries, papillary muscles and moderator band were incorporated. For each subject, His-Purkinje mediated activation with (RBBB/LBBB) and without (normal) conduction defect were simulated. Corresponding 67-lead body surface potentials (BSP) were computed and used as input for both iECG techniques. Estimated activation sequences of both iECG techniques were compared to simulated activation sequences. In one subject, 67-lead BSP measurement was performed during His-Purkinje mediated activation and used as input for both iECG techniques. For this subject, iECG estimated maps were compared to invasive mapping.
Results: Figure 1 displays an example of the estimation of normal activation. Mean inter-map correlation between simulated and estimated activation sequences for multi-focal iECG vs. multi-wave iECG was 59±36% vs. 86±7% for normal activation, 79±8% vs. 72±17% for RBBB activation and 41±31% vs. 62±25% for LBBB activation. In the subject with measured BSP and invasive mapping, epicardial inter-map correlation between invasive and iECG maps was -4±8% for multi-focal iECG and 65±1% for multi-wave iECG.
Conclusion: This study shows improved performance of multi-wave iECG for the estimation of His-Purkinje mediated activation sequences with and without conduction defect. Future research focusses on further validation of multi-wave iECG using invasive mapping.