Atrial flutter

This illustration shows atrial flutter with a variable block (between 5:1 and 4:1). Atrial flutter is a type of abnormal heart rhythm characterised by a rapid and regular atrial rate.

Image by James Heilman, MD and derivative work by Mysid. Licensed under the CC BY-SA 3.0. Source: Wikimedia Commons. Created on 13 October 2012.

Definition

Atrial Flutter is an abnormal heart rhythm (arrhythmia) originating in the upper chambers of the heart (atria). It is characterised by a rapid and regular atrial rate, typically around 250–350 beats per minute, leading to an irregular or fast pulse.

Aetiology

Common causes of atrial flutter include:

Heart Conditions: E.g., ischaemic heart disease, heart failure, or valvular heart disease.
Hypertension: Long-standing high blood pressure.
Thyroid Disorders: Particularly hyperthyroidism.
Lung Diseases: Chronic obstructive pulmonary disease (COPD) or pulmonary embolism.
Post-Surgery: Common after cardiac surgery.
Alcohol Consumption: Particularly binge drinking ("holiday heart syndrome").

Pathophysiology

Atrial flutter occurs due to abnormal electrical activity in the atria:

Re-entry Circuit: A continuous electrical loop within the atria causes rapid and repetitive atrial contractions.
Ventricular Response: The atrioventricular (AV) node limits how many atrial signals reach the ventricles, often resulting in a 2:1 conduction ratio (e.g., atrial rate of 300 bpm with a ventricular rate of 150 bpm).
This inefficient pumping reduces cardiac output and may lead to blood pooling in the atria, increasing the risk of clots.

Risk Factors

Risk factors include:

Ageing, as atrial flutter is more common in older adults.
Existing heart conditions, such as heart failure or coronary artery disease.
High blood pressure.
Thyroid disorders, particularly overactive thyroid (hyperthyroidism).
Lung diseases like COPD or pulmonary embolism.
Alcohol consumption or binge drinking.

Signs and Symptoms

Symptoms of atrial flutter include:

Palpitations: Feeling of a fast or irregular heartbeat.
Fatigue: Due to reduced cardiac output.
Shortness of Breath: Especially on exertion.
Dizziness or Lightheadedness: Due to reduced blood flow to the brain.
Chest Discomfort: Rarely, this may mimic angina.
Stroke Symptoms: Sudden weakness or difficulty speaking, if clots form and embolise.

Investigations

Key investigations include:

Electrocardiogram (ECG):
- Shows a "sawtooth" pattern of flutter waves, especially in leads II, III, and aVF.
- May show a regular or irregular ventricular rhythm, depending on AV node conduction.
Blood Tests:
- Thyroid Function Tests: To rule out hyperthyroidism.
- Electrolytes: To detect abnormalities like low potassium or magnesium.
Echocardiography: To assess heart structure and rule out underlying valvular or structural abnormalities.
24-hour Holter Monitoring: To capture intermittent episodes of atrial flutter.

Management

1. Rate Control

Beta-blockers: E.g., bisoprolol to slow the heart rate.
Calcium Channel Blockers: E.g., diltiazem, particularly if beta-blockers are not suitable.

2. Rhythm Control

Electrical Cardioversion: A controlled shock delivered to restore normal rhythm, particularly in unstable patients.
Antiarrhythmic Drugs: E.g., amiodarone, used under specialist guidance to maintain sinus rhythm.

3. Anticoagulation

Anticoagulants (e.g., apixaban, rivaroxaban) to reduce the risk of stroke in patients with a CHA₂DS₂-VASc score ≥2.

4. Specialist Referral

Referral for catheter ablation, which targets and disrupts the re-entry circuit, may be considered for recurrent or symptomatic atrial flutter.

Patient Advice

Key advice includes:

Take prescribed medications consistently to manage symptoms and reduce complications.
Adopt a heart-healthy lifestyle, including a balanced diet and regular exercise.
Avoid excessive alcohol consumption, which can trigger atrial flutter.
Seek urgent medical attention if symptoms such as severe breathlessness or chest pain occur.

Cardiologymypanotes30 January 2025Atrial flutter