Influence of paper electrocardiogram digitizing on T wave and QRS complex morphology parameters.

Background: Many morphological parameters of the electrocardiogram (ECG) can be calculated from a digital ECG and paper prints of ECG after digitizing. However, the digitizing process, including printing, scanning, ECG contour extraction, and alignment, can produce changes to the signals, reducing the reliability of some sensitive parameters of QRS complex and T wave.

Methods: The influence of the digitizing process on the parameters of T wave and QRS complex morphology was studied by comparing systematically the values of the nine ECG morphology parameters, computed from the digital ECG and the corresponding paper ECG. The robustness of the parameters to the digitizing process and their discrimination ability between healthy subjects and postinfarction patients were investigated.

Results: The standard T wave parameters and all selected dipolar loop-parameters retained their robustness and discrimination ability during the digitizing process of the paper ECGs. The non-dipolar parameters distorted strongly, especially those of the QRS complex. The T wave-based non-dipolar parameters retained their discrimination ability during the digitizing process.

Conclusions: The selected standard T wave parameters and the dipolar loop-parameters calculated from properly digitized ECG paper prints can be utilized in patient studies. Non-dipolar parameters distort strongly but T wave-based parameters retain discriminatory information.