Mechanism of atrial sounds in atrial fibrillation. Phonoechocardiographic correlation. Report of a case.

Audible atrial sounds were noted in a patient with congestive cardiomyopathy and atrial fibrillation with slow ventricular rate. Oscillatory motion of similar periodicity as fibrillation waves in the ECG and the sounds in the phonocardiogram was demonstrated in aortic and left ventricular walls, mitral, tricuspid and aortic leaflets by echocardiography. This suggests that the fibrillation motion of the atria is forceful enough to cause vibration of the cardiohemic system resulting in the audible sounds.