Atrial activation time determined by transthoracic Doppler tissue imaging can be used as an estimate of the total duration of atrial electrical activation.

Background: Currently, the total atrial activation time, as indicated by the P-wave duration using signal-averaged (SA) electrocardiogram (ECG) (SA-ECG), is the most powerful predictor of atrial fibrillation. However, because of practical limitations, this technique is not used in clinical routine. In this study we evaluated several alternative techniques to measure the total atrial activation time, including a new parameter that uses atrial Doppler tissue imaging (DTI).
Methods: For 30 patients who were in sinus rhythm and underwent a transthoracic echocardiogram, we determined the P-wave duration on surface ECG and SA-ECG, and the interval from the onset of the P wave (lead II) until the onset of the echocardiographic flow Doppler A wave over the mitral valve. In addition, using pulsed wave DTI in the 4-chamber view, we measured the interval of time from initiation of the ECG P wave (lead II) until the peak of the local lateral left atrial (LA) DTI signal. Correlation between the SA-ECG, surface ECG, and echocardiographic parameters were evaluated by Spearman correlation tests.
Results: All parameters that were used to estimate total atrial activation time showed a significant correlation with the SA-ECG P-wave duration. Although the interval of time from initiation of the ECG P wave until the peak of the local lateral LA DTI signal was significantly longer than the SA-ECG P-wave duration (151.12 +/- 19.4 vs 128.4 +/- 15.8 milliseconds, respectively, P < .01), it showed the highest correlation (R = 0.91, P < .001). There was no significant correlation between the SA-ECG and routine echocardiographic parameters such as LA, right atrial, or total atrial size. Measurement of the interval of time from initiation of the ECG P wave until the peak of the local lateral LA DTI signal added 1 +/- 0.5 minutes to a routine echocardiographic evaluation, whereas measurement of the SA-ECG P-wave duration took 20 +/- 5 minutes (P < .01).
Conclusion: LA DTI is an easy, fast, and reliable method to estimate the total atrial electrical activation time, and may be useful in the identification of those prone to develop atrial fibrillation.