Dissimilar atrial rhythms diagnosed by echocardiography

A 27-year-old woman with ectopic atrial rhythm and apparent atrioventricular dissociation was found to have A waves on the mitral echocardiogram that bore no relation to the P wave on the surface electrocardiogram. The ECG did not reflect the presence of dissimilar atrial rhythms, and their presence became apparent only during the echocardiographic studies. The mechanism of this phenomenon and its clinical implications are discussed.