A Study on Atrial Ta Wave Morphology in Healthy Subjects: An Approach Using P Wave Signal-Averaging Method

Introduction: Filtered and unfiltered signal-averaged P wave analyses are in existence for the detailed study on the P wave morphology. Information on the atrial repolarization (Ta wave) is seldom explained. Objective: In the present study, Modified Limb Lead (MLL) ECGs were recorded and studied using unfiltered signal-averaged P wave analysis to better describe the atrial P and Ta wave morphology. In addition, a novel algorithm is proposed for the R wave peak detection from the recorded MLL ECG. Methods: Sixty healthy male subjects (mean age 39 years) were included in this study. MLL ECGs were recorded with BIOKIT INDIA ECG (3-lead) system and EDAN SE-1010 PC ECG system. Unfiltered signal-averaged P wave analysis was used to investigate the measured P and Ta wave peak amplitude and duration. Results: The average P wave duration was 91 +/- 2.6 ms. The observable Ta wave duration was 109 +/- 4.7 ms, the P-Ta interval was 198 +/- 2.9 ms and the corrected P-Ta interval was 241 +/- 4.7 ms. The P wave and the Ta wave amplitude was 117 +/- 23 mu V and 43 +/- 12 mu V respectively. The Ta wave maxima was located at 150 +/- 5.7 ms. Significant correlation was found between the values of P wave and Ta wave amplitude (r = 0.30, P = 0.01). Conclusion: The Ta wave was clearly observed in the healthy subjects using the MLL system with better beat averaging. The Ta wave was opposite in polarity to the P wave and longer in duration. The Ta wave maxima are generally located in the PR interval during normal AV conduction. The P and Ta wave duration was altered due to increase in age. The P-Ta interval shortened with increasing heart rate. The proposed algorithm showed excellent P and R peak detection.