Total atrial conduction time (TACT) denotes the total period required for atrial activation. Conventionally it is measured using signal averaged electrocardiogram (SA-ECG) as the maximal P wave duration. It has been shown to be powerful predictor of atrial fibrillation. A simpler method which can be done in any echocardiography laboratory without the use of SA-ECG is a tissue Doppler and surface ECG combined measurement of atrial activation. PA-TDI is measured from the onset of the P wave on surface ECG to the tissue Doppler derived peak of A wave at the lateral left atrial wall). PA-TDI has been shown to predict new onset atrial fibrillation (AF), recurrence of AF after ablation, AF after acute myocardial infarction and even AF after cardiac surgery . Cardiac surgeries in which PA-TDI has been successfully used to predict AF include coronary artery bypass grafting (CABG), aortic valve replacement (AVR) for aortic stenosis  and surgery for mitral regurgitation .
In mitral regurgitation, prediction of AF is very important as the left atrium is very large. Onset of AF after relief of mitral regurgitation jet which has a cleansing action on the left atrium may lead to thrombus formation and increase the risk of stroke and other systemic embolism .