Optimal lead configuration in the detection and subtraction of QRS and T wave templates in atrial fibrillation

An in-house written software package was used to generate templates of QRS complexes and T waves using self-similarity techniques, and leave a residual signal representing only atrial activity. The templating performance differences between individual ECG leads were tested. The mean number of templates in each of the 3 ECG leads was 8±4, 2±1, 7±5 for the QRS complexes, and 11±5, 11±8, 10±5 for the T waves. Lead 2 generated less QRS templates than 2 other leads, left less unmatched QRS complexes and T waves (all p<0.005). The average correlation coefficients between templates were 0.69±0.27, 0.21±0.36, and 0.63±0.27 respectively for QRS complexes, and 0.33±0.24, 0.46±0.31, and 0.50±0.24 respectively for T wave in leads 1, 2, and 3. These data suggest that the QRS subtraction process performed well. Lead 2 (a bipolar V5) performed best, but optimal subtraction may require more templates, and hence auto-tuning by the algorithm to the signal encountered