Atrial Flutter and Heart Rate

Introduction

Atrial flutter (AFL) is a type of abnormal heart rhythm (arrhythmia) that originates in the atria, the upper chambers of the heart. It is characterized by a rapid and regular atrial rate, which typically ranges between 250-350 beats per minute (bpm). However, the actual heart rate (ventricular rate) that is measured in the patient depends on how many of these impulses are conducted to the ventricles.

Mechanism of Atrial Flutter

Atrial flutter is caused by a reentrant circuit in the atria, most commonly in the right atrium. This leads to a continuous cycle of electrical activity that results in the characteristic sawtooth pattern seen on an electrocardiogram (ECG).

Ventricular Response in Atrial Flutter

Since the atrioventricular (AV) node limits how many impulses reach the ventricles, the ventricular rate is usually lower than the atrial rate. The most common ventricular rates in untreated atrial flutter are: - 2:1 AV conduction -> Ventricular rate around 150 bpm - 3:1 AV conduction -> Ventricular rate around 100 bpm - 4:1 AV conduction -> Ventricular rate around 75 bpm

In some cases, the ventricular rate can become dangerously fast, especially if there is an underlying conduction disorder or another arrhythmia like atrial fibrillation.

Symptoms of Atrial Flutter

Patients with atrial flutter may experience: - Palpitations - Shortness of breath - Dizziness or lightheadedness - Fatigue - Chest discomfort

Diagnosis

Atrial flutter is diagnosed using an ECG, which shows the characteristic “sawtooth” flutter waves in leads II, III, and aVF. Other tests that may help include: - Holter monitoring - Echocardiography to assess heart structure and function - Blood tests to check for electrolyte imbalances or thyroid disorders

Treatment Options

1. Rate Control

• Medications like beta-blockers (e.g., metoprolol) or calcium channel blockers (e.g., diltiazem) to slow the ventricular response.

2. Rhythm Control

• Electrical Cardioversion: A procedure that delivers a controlled shock to restore normal rhythm.
• Medications: Such as class III antiarrhythmics (amiodarone, sotalol) to help maintain sinus rhythm.

3. Catheter Ablation

• Radiofrequency ablation is the preferred long-term solution for recurrent atrial flutter. It targets the reentrant circuit and can cure the condition in many cases.

4. Anticoagulation

• Patients with AFL are at risk of stroke, especially if risk factors like hypertension, diabetes, or previous stroke are present.
• Anticoagulants (e.g., warfarin or DOACs like apixaban) are often prescribed depending on stroke risk assessment (CHA₂DS₂-VASc score).

Conclusion

Atrial flutter is a common arrhythmia that can lead to significant symptoms and complications if left untreated. Proper diagnosis with ECG and management with rate or rhythm control, ablation, and anticoagulation can improve quality of life and reduce stroke risk.

Source recommendations

1. 2023 American College of Cardiology/American Heart Association/Heart Rhythm Society Guideline for the Management of Patients With Atrial Fibrillation

1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
2. https://pubmed.ncbi.nlm.nih.gov/38033089/
3. https://www.hrsonline.org/guidance/clinical-resources/2023-accahaaccphrs-guideline-diagnosis-and-management-patients-atrial-fibrillation
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.heartrhythmjournal.com/article/S1547-5271(23)02246-4/fulltext

2. 2020 European Society of Cardiology Guidelines for the Diagnosis and Management of Atrial Fibrillation

1. https://pubmed.ncbi.nlm.nih.gov/32860505/
2. https://academic.oup.com/eurheartj/article/42/5/373/5899003
3. https://www.escardio.org/static-file/Escardio/Guidelines/Documents/ehaa612.pdf
4. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
5. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Atrial-Fibrillation