How many electrodes and where? A "poldermodel" for electrocardiography.

It is known that body surface potential maps (BSPMs) contain diagnostic information not easily retrieved from the standard 12-lead electrocardiogram (ECG). Alternate lead sets that can reconstruct the BSPM have been proposed, but they are impractical because they require more than the 10 electrodes of the standard ECG and use nonstandard positions. We propose a practical approach to increasing the diagnostic information content of the standard ECG by repositioning selected chest electrodes. Thus, in the best tradition of the Dutch "poldermodel," we have sought to strike a compromise between the demands of different parties, one that, while suboptimal for each, will be seen by all as the best attainable result. We used a set of 746 120-lead BSPMs from healthy individuals and patients with various abnormalities. Data were split in a learning and a test set. Using the learning set, a general transformation to reconstruct all BSPM leads from the standard 12-lead ECG was derived by linear regression. Similarly, BSPMs were reconstructed when 2 of electrodes V(3)-V(6) were moved to other positions on the anterior part of the chest. Reconstruction performance was assessed on the test set by correlation and similarity coefficients. Thanks to the redundancy of information in the precordial leads, 2 missing precordial leads can be reconstructed from the others, using general coefficients, to a high degree of accuracy, particularly when the missing leads were not adjacent. We chose to reposition V(4) and V(6) to different sites on the anterior thorax. From the many electrode sites that we explored, those at 2 intercostal spaces below and above V(2) yielded better BSPM reconstruction than was attainable from the standard electrode positions, in most parts of the anterior thorax, including regions that are known to contain important diagnostic information less well brought forward by the standard ECG. Slight variations in the new electrode positions did not appreciably change the results. The standard 12-lead ECG proved to produce better overall reconstructions than either the EASI configuration or vectorcardiographic lead systems. Repositioning electrodes V(4) and V(6) provides a simple, practical method by which to improve the sampling of diagnostic information from the body surface while maintaining the full diagnostic content of the standard 12-lead ECG. This approach also obviates the need to determine the precise location of V(4) electrode, which may be difficult in women.