Epicardial excitation of the atria in a patient with atrial flutter.

Atrial epicardial excitation mapping was performed during open heart operation in a patient with atrial flutter and rheumatic mitral and aortic valve disease. Though it was impossible to study completely the epicardial excitation of both atria, our results do exclude a circus movement involving a large part of the atria. The two possible mechanisms responsible for the atrial flutter in our patient were: (i) an ectopic focus located low in the atrium; and (2) a reciprocal rhythm situated in a small area low in the atrium or upper part of the A V junction.