This ECG (11) shows a narrow complex tachycardia at a rate of 143 per minute- Deep
negative atrial waves are seen in the inferior leads, one in the usual position of the P wave and another just following the ORS complex-
The negative nadirs have a regular rhythm with a rate of 286 per minute- Small upright
atrial waves are seen in V1, one just preceding the QRS and the other closely
following the previous ORS, also having a regular rhythm at a rate of 286 per minute.
This pattern is typical of atrial flutter with 2:1 conduction ratio.
Atrial flutter with 2:1 conduction ratio is often misdiagnosed because it is somewhat
difficult to appreciate the atrial waveform when most of the atrial activity is superimposed on either the ORS complex or the T wave. Slowing the ventricular rate
transiently with carotid sinus pressure or adenosine administration reveals the typical
continuous atrial waveform
Atrial flutter is characterized by an atrial waveform that is regular in rhythm. constant
in waveform. and is a continuous undulation in the inferior Iimb leads rather than discrete P waves- ln V1 on the other hand. there are discrete waves separated by isoelectric periods. The atrial rate may vary widely. But is often very close to 300 per minute.
Three types of atrial flutter have been described. The common form of classical
atrial flutter usually has an atrial rate in the range of 260 to 320 per minute. unless slowed by antiarrhythmic drugs or by marked enlargement of the right atrium. The atrial waveform features sharp negative nadirs in the inferior leads and resembles a sawtooth. or a picket fence. The mechanism of the common form of classical flutter is a macro reentrant circuit around virtually the entire right atrium. in a counterclockwise direction-
A critical part of the circuit is a zone of slow conduction in the isthmus area of the low
right atrium. between the inferior vena caval orifice and the tricuspid annulus.
An uncommon form of classical flutter exists. in which the waveform appears to have
predorninantly positive waves in the inferior leads but is otherwise similar to the common form. The uncommon form usually has a circuit in the clockwise direction.
The third form of atrial flutter (Type II flutter) is characterized by faster atrial rates. in the range of 340 to 440 per minute and also by an inability to be terminated by atrial overdrive pacing.
Classical atrial flutter can usually be controlled by radio frequency catheter
ablation. which produces a block in the slowly conducting isthmus-
Puech P. Latour H. Grolleau R. Le flutter et ses lirnits- Arch Mal Coeur Vaiss
Schwartzman D. Callans DJ. Gottlieb CD. Dillon SM. Movsowitz C. Marchlinski FE-
Conduction block in the inferior vena cavaltricuspid valve isthmus: association with
outcorne of radiofrequency ablation of type l atrial flutter- J Am Coll Cardiol
Waldo AL- Atrial flutter. ln: Podrid PJ. Kowey PR. eds. Cardiac Arrhythmia Mechanisms- Diagnosis and management- Baltimore
Williams & Wilkins: 1995:p. 791 -802- WeIIs JL. MacLean WA- James TN- Waldo AL- Characterization of atrial flutter- Studies in rnan after open heart surgery using fixed atrial electrodes- Circulation 1979:60:665-73