ATRIAL FLUTTER
● Characterized by a large (macro) re-entry circuit, usually within the right atrium
encircling the tricuspid annulus.
● The atrial rate is typically 300 beats per minute.
● Usually associated with 2:1, 3:1 or 4:1 AV Block
PATHOPHYSIOLOGY OF ATRIAL FLUTTER
• Atrial flutter is a form of supraventricular tachycardia caused by a re-entry circuit within
the right atrium. The length of the re-entry circuit corresponds to the size of the right
atrium, resulting in a fairly predictable atrial rate of around 300 bpm (range 200-400).
• Ventricular rate is determined by the AV conduction ratio (“degree of AV block”). The
most common AV ratio is 2:1, resulting in a ventricular rate of approximately 150 bpm.
• Higher-degree blocks can occur — usually due to medications or underlying heart disease
— resulting in lower rates of ventricular conduction, e.g., 3:1 or 4:1 block.
• Atrial flutter with 1:1 conduction can occur due to sympathetic stimulation, or in the
presence of an accessory pathway. The administration of AV-nodal blocking agents to a
patient with WPW can precipitate this.
• Atrial flutter with 1:1 conduction is associated with severe hemodynamic instability and
progression to ventricular fibrillation
• NB. The term “AV block” in the context of atrial flutter is something of a misnomer. AV
block is a physiological response to rapid atrial rates and implies a normally functioning
AV node.
, ECG FEATURES OF ATRIAL FLUTTER
• Narrow complex tachycardia
• Regular atrial activity at ~300 bpm
• “Saw-tooth-flutter wave” pattern of inverted flutter waves in leads II, III, aVF
• Upright flutter waves in V1 that may resemble P waves
• Loss of the isoelectric baseline
• Ventricular rate depends on AV conduction ratio
CLASSIFICATION
● Typical atrial flutter (Common, or Type I Atrial Flutter)
Involves the IVC & tricuspid isthmus in the reentry circuit. Can be further classified based
on the direction of the reentry circuit (anticlockwise or clockwise):
1. Anticlockwise Reentry: Commonest form of atrial flutter (90% of cases). Retrograde
atrial conduction produces:
• Inverted flutter waves in leads II, III, aVF
• Positive flutter waves in V1 – may resemble upright P waves
2. Clockwise Reentry: This uncommon variant produces the opposite pattern:
• Positive flutter waves in leads II, III, aVF
• Broad, inverted flutter waves in V1
● Atypical atrial flutter (Uncommon, or Type II Atrial Flutter)
• Does not fulfill criteria for typical atrial flutter
• Often associated with higher atrial rates and rhythm instability
• Less amenable to treatment with ablation
● Characterized by a large (macro) re-entry circuit, usually within the right atrium
encircling the tricuspid annulus.
● The atrial rate is typically 300 beats per minute.
● Usually associated with 2:1, 3:1 or 4:1 AV Block
PATHOPHYSIOLOGY OF ATRIAL FLUTTER
• Atrial flutter is a form of supraventricular tachycardia caused by a re-entry circuit within
the right atrium. The length of the re-entry circuit corresponds to the size of the right
atrium, resulting in a fairly predictable atrial rate of around 300 bpm (range 200-400).
• Ventricular rate is determined by the AV conduction ratio (“degree of AV block”). The
most common AV ratio is 2:1, resulting in a ventricular rate of approximately 150 bpm.
• Higher-degree blocks can occur — usually due to medications or underlying heart disease
— resulting in lower rates of ventricular conduction, e.g., 3:1 or 4:1 block.
• Atrial flutter with 1:1 conduction can occur due to sympathetic stimulation, or in the
presence of an accessory pathway. The administration of AV-nodal blocking agents to a
patient with WPW can precipitate this.
• Atrial flutter with 1:1 conduction is associated with severe hemodynamic instability and
progression to ventricular fibrillation
• NB. The term “AV block” in the context of atrial flutter is something of a misnomer. AV
block is a physiological response to rapid atrial rates and implies a normally functioning
AV node.
, ECG FEATURES OF ATRIAL FLUTTER
• Narrow complex tachycardia
• Regular atrial activity at ~300 bpm
• “Saw-tooth-flutter wave” pattern of inverted flutter waves in leads II, III, aVF
• Upright flutter waves in V1 that may resemble P waves
• Loss of the isoelectric baseline
• Ventricular rate depends on AV conduction ratio
CLASSIFICATION
● Typical atrial flutter (Common, or Type I Atrial Flutter)
Involves the IVC & tricuspid isthmus in the reentry circuit. Can be further classified based
on the direction of the reentry circuit (anticlockwise or clockwise):
1. Anticlockwise Reentry: Commonest form of atrial flutter (90% of cases). Retrograde
atrial conduction produces:
• Inverted flutter waves in leads II, III, aVF
• Positive flutter waves in V1 – may resemble upright P waves
2. Clockwise Reentry: This uncommon variant produces the opposite pattern:
• Positive flutter waves in leads II, III, aVF
• Broad, inverted flutter waves in V1
● Atypical atrial flutter (Uncommon, or Type II Atrial Flutter)
• Does not fulfill criteria for typical atrial flutter
• Often associated with higher atrial rates and rhythm instability
• Less amenable to treatment with ablation
