Tachycardia mediated atrial cardiomyopathy is the term sometimes used to denote atrial mechanical stunning after reversion of persistent atrial arrhythmias like atrial fibrillation or atrial flutter to sinus rhythm. This can persist for a variable period of time and can be documented by assessing left atrial appendage emptying velocity by Doppler studies. The intrinsic late diastolic contraction of the left atrial appendage produces the so-called “a”-wave, which is seen as a positive flow (directed toward the transducer) on trans esophageal echocardiography and appears just after the P wave on the electrocardiogram. This wave occurs simultaneously with the A wave of mitral inflow. There is no correlation between the velocities of the left atrial appendage a wave and the mitral inflow A wave. Left atrial appendage a wave is the largest wave in sinus rhythm with normal left atrial appendage function. It correlates with the ejection fraction of the left atrial appendage. In post cardioversion atrial stunning (tachycardia mediated atrial cardiomyopathy) the e wave due to passive left atrial appendage emptying becomes preponderant. This e wave is caused by a combination of factors which include passive compression induced by left ventricular relaxation, passive suction effect due to opening of the mitral valve and the rapid emptying of the left atrium in early diastole.