Overview
Atrial flutter is most commonly due to a right atrial macro-reentrant circuit, and has significant crossover with atrial fibrillation in its pathogenesis.
Pathogenesis
Mechanism
- Typical atrial flutter occurs as a macro-reentrant circuit around the tricuspid valve annulus, most commonly in a counter-clockwise direction. The slow aspect of the sawtooth wave occurs as the impulse is conducted through the cavotricuspid isthmus.
Reverse typical atrial flutter is where the reentrant circuit travels in a clockwise direction. There are also several types of atypical atrial flutter, caused by a variety of other reentrant circuits.
Causes of Atrial Flutter
- Severe acute illness - especially in septic or postoperative patients
- Cardiac - post cardiac surgery, myocardial infarction, valvular disease, cardiomyopathy, congestive cardiac failure, congenital heart disease, Wolff-Parkinson-White
- Cardiovascular risk factors - hypertension, diabetes, obesity
- Pulmonary embolism
- Obstructive sleep apnoea
- Thyrotoxicosis
- Alcohol abuse
Diagnosis
ECG Findings
- Heart rate ~150bpm
- Regular rhythm (RR interval)
- Saw-toothed baseline 'flutter' waves at ~300bpm
- Atrioventricular block (not every flutter wave is followed by a QRS complex)
In typical atrial flutter, 2:1 AV block is present with every second flutter wave resulting in a QRS complex. The block may also be 3:1, 4:1 or variable. 1:1 conduction is associated with extreme tachycardia and is immediately life-threatening.
- Atrial flutter with 3:1 block:
![Atrial flutter with 31 block]()
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