Understanding ECG in Atrial Flutter

Introduction

Atrial flutter is a type of arrhythmia that originates in the atria, the upper chambers of the heart. It is characterized by a rapid but regular electrical activity, leading to inefficient atrial contractions and abnormal ventricular response.

Electrocardiography (ECG) is the primary diagnostic tool for atrial flutter, as it helps identify the distinct electrical patterns typical of this condition.

ECG Features of Atrial Flutter

1. Flutter Waves (F-waves)

• Unlike normal P waves seen in a regular heart rhythm, atrial flutter presents as sawtooth-shaped flutter waves.
• These waves are best seen in leads II, III, and aVF.
• The atrial rate is typically around 250–350 beats per minute (bpm).

2. Ventricular Rate and Conduction Patterns

• The AV node only allows a fraction of atrial impulses to reach the ventricles, commonly in ratios like 2:1 (most common), 3:1, or 4:1 conduction.
• A 2:1 conduction results in a ventricular heart rate of around 150 bpm.

3. Lack of an Isoelectric Baseline

• A key feature is the absence of a flat baseline between flutter waves.

4. Regular Rhythm (Unless Variable Block is Present)

• Unlike atrial fibrillation (which is irregular), atrial flutter often presents with a regular ventricular rhythm, depending on conduction.

Causes of Atrial Flutter

Atrial flutter is often associated with: - Structural heart diseases (e.g., atrial enlargement, valve disease, cardiomyopathy) - Hypertension - Ischemic heart disease - Chronic lung disease - Hyperthyroidism - Alcohol use (“holiday heart syndrome”) - Post-cardiac surgery or procedure complications

Clinical Symptoms

Patients may experience: - Palpitations - Shortness of breath - Dizziness or near-syncope - Fatigue

However, some cases are asymptomatic and only detected via ECG.

Treatment Options

1. Rate Control

• Beta-blockers (e.g., metoprolol) or calcium channel blockers (e.g., diltiazem) are used to slow down the ventricular response.

2. Rhythm Control

• Electrical cardioversion is often used for restoring normal sinus rhythm.
• Class IC and III antiarrhythmic drugs (like flecainide or amiodarone) may be used to maintain sinus rhythm.

3. Ablation Therapy

• Catheter ablation is often a curative approach, targeting the reentrant circuit in the right atrium.

4. Anticoagulation

• Patients with atrial flutter have an increased risk of stroke, so anticoagulation therapy (e.g., warfarin, NOACs) may be required based on CHA₂DS₂-VASc criteria.

Conclusion

ECG interpretation is crucial for diagnosing atrial flutter, which is characterized by sawtooth waves and a regular but often rapid ventricular rate. Understanding the underlying cause and choosing the appropriate management strategy—whether rate control, rhythm control, or ablation—are essential for optimizing patient outcomes.

Source recommendations

1. American College of Cardiology/American Heart Association (ACC/AHA) Guideline for Management of Atrial Flutter

1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
2. https://www.acc.org/Latest-in-Cardiology/ten-points-to-remember/2020/12/04/20/16/2020-Update-to-ACC-AHA-AF-AFL-Performance
3. https://www.sciencedirect.com/science/article/pii/S073510970101587X
4. https://www.acc.org/Latest-in-Cardiology/ten-points-to-remember/2023/11/27/19/46/2023-acc-guideline-for-af-gl-af
5. https://www.jacc.org/guidelines/atrial-fibrillation

2. European Society of Cardiology (ESC) Guidelines for Management of Supraventricular Tachycardia

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
2. https://academic.oup.com/eurheartj/article/41/5/655/5556821
3. https://pubmed.ncbi.nlm.nih.gov/31504425/
4. https://www.acc.org/Latest-in-Cardiology/ten-points-to-remember/2019/09/10/12/36/2019-ESC-Guidelines-for-Supraventricular-Tachycardia
5. https://pubmed.ncbi.nlm.nih.gov/14563598/