10-33: Atrial Flutter

Various ECG patterns produced by atrial flutter. A: A trial flutter showing the typical sawtoothed pattern is present. The atrial rate is unusually slow at about 220/min. The flutter waves deform the ST segments, mimicking ST elevation (arrows). Careful attention to the variation in QRST morphology should provide a clue to the correct diagnosis. The ventricular rate shows group beating characteristic of type I (Wenckebach) second-degree block of the flutter impulses. Type I atrioventricular (AV) block of flutter impulses that occurs within the AV node has no clinical significance since the AV nodal block often occurs in response to rapid atrial rates. B: F lutter waves superimposed upon QRS complexes deform them (arrows), mimicking an intermittent intraventricular conduction delay. Careful measurement of the atrial rate provides evidence that the wave deforming the downstroke of the QRS complexes is a flutter wave. Note the unusually slow flutter rate of about 190/min. C: F lutter waves having the same amplitude as the QRS complexes (arrows) mimic a period of ventricular asystole. Simultaneous recording of other leads will more clearly define the QRS complexes. D: Flutter waves superimposed upon the downstrokes of the QRS complexes (arrows) mimic ST-segment depression. E: Flutter waves occurring at the ends of the QRS complexes (arrows) mimic a Qr configuration and an intraventricular conduction delay. Since the ventricular rate is regular at 150/min, the diagnosis of atrial flutter with 2:1 AV conduction should always be strongly considered. (Reproduced, with permission, from Goldschlager N, Goldman MJ. Principles of Clinical Electrocardiography, 13th ed. Originally published by Appleton & Lange. Copyright © 1989 by The McGraw-Hill Companies, Inc.)