Left atrial impulse formation in atrial flutter.

Abstract
Four cases of atrial flutter of left atrial origin are reported. The ecg was characterized by distinctive dome and dart P waves in lead V1 and inverted P waves in leads I and V6. Vectorial analysis of atrial activation located the ectopic focus in the posterior portion of the left atrium. The possible role of left atrial automaticity in the genesis of atrial flutter is discussed.