Makindo Medical Notes

Related Subjects: |Wolff-Parkinson White syndrome (WPW) AVRT |Lown Ganong Levine Syndrome AVRT |Supraventricular Tachycardia (SVT) |Atrioventricular Nodal Reentrant Tachycardia AVNRT |Atrial Flutter |Atrial Fibrillation |Sinus Tachycardia |Sinus Arrhythmia |Multifocal Atrial Tachycardia |Resuscitation - Adult Tachycardia Algorithm

Important: Class I and III antiarrhythmic drugs should not be administered until the heart rate is controlled using digoxin, beta-blockers, or calcium channel blockers. These drugs can slow the flutter rate, potentially leading to dangerous 1:1 conduction. Catheter ablation, which targets the reentrant circuit responsible for typical atrial flutter, has a success rate exceeding 90% in preventing recurrence.

About Atrial Flutter

• Atrial flutter is an atrial arrhythmia characterized by a rapid atrial rate of 280–350 beats per minute.
• Always suspect atrial flutter if the ventricular rate is approximately 150 beats per minute, especially in patients with no evidence of accessory pathways.
• Commonly associated with atrial fibrillation, and patients may alternate between the two rhythms (atrial fibrillation–flutter).

Aetiology

• Atrial flutter is a macro-reentrant arrhythmia typically involving the right atrium.
• May occur in structurally normal hearts or be associated with underlying cardiac or systemic conditions.
• Risk factors include prior atrial fibrillation, hypertension, coronary artery disease, and valvular heart disease.

ECG Appearances

ECG Findings

• Sawtooth Pattern: A characteristic sawtooth appearance of atrial activity, often best seen in the inferior leads (II, III, aVF).
• 1:1 AV Conduction: Ventricular rate of 300 bpm (rare but life-threatening due to reduced cardiac output).
• 2:1 AV Block: Ventricular rate of 150 bpm (most common presentation).
• 3:1 AV Block: Ventricular rate of 100 bpm.
• 4:1 AV Block: Ventricular rate of 75 bpm.
• Carotid sinus massage or adenosine can transiently increase AV block, making flutter waves more apparent.

Types of Atrial Flutter

• Type I (Typical): Caused by a macro-reentrant tachycardia circuit within the right atrium, usually around the tricuspid annulus (cavo-tricuspid isthmus dependent).
• Type II (Atypical): Involves non-cavo-tricuspid isthmus-dependent circuits and is often associated with prior atrial surgery or ablation.

Causes

• Idiopathic atrial flutter
• Pulmonary embolism
• Atrial septal defect
• Ischaemic heart disease
• Hypertension
• Cardiomyopathy
• Chronic obstructive pulmonary disease (COPD)
• Post-cardiac surgery
• Pericarditis
• Thyrotoxicosis
• Alcohol intoxication ("holiday heart syndrome")

Clinical Presentation

• May be asymptomatic, especially if the ventricular rate is well controlled.
• Common symptoms include palpitations, fatigue, shortness of breath, dizziness, or lightheadedness.
• Severe cases may present with hemodynamic instability, syncope, or heart failure symptoms.

Investigations

• Blood Tests: FBC, U&E, TFTs, CRP. Troponin and BNP levels may also help assess for cardiac stress or failure.
• ECG: Essential for diagnosis. Suspect atrial flutter in tachyarrhythmias with a ventricular rate of 150 bpm. Adenosine or carotid sinus massage may help unmask flutter waves.
• Echocardiogram: Evaluate left ventricular function, atrial size, valve pathology, and potential structural abnormalities.
• Holter Monitoring: Useful for detecting intermittent atrial flutter or related arrhythmias.

Management: See below

• Synchronized DC Cardioversion: First-line treatment for patients who are hemodynamically unstable.
• Rate Control: Achieved using beta-blockers, calcium channel blockers, or digoxin.
• Rhythm Control: Amiodarone or flecainide can help restore sinus rhythm, but caution is needed due to the risk of 1:1 conduction.
• Catheter Ablation: Gold-standard treatment for long-term management, with a high success rate for preventing recurrence.
• Anticoagulation: Assess stroke risk using CHA₂DS₂-VASc score and consider anticoagulation to reduce thromboembolic risk.
• Adjunctive Measures: Lifestyle modifications, including limiting alcohol intake and treating underlying conditions such as COPD or thyrotoxicosis, are essential for long-term management.

Contraindicated Drugs in Atrial Flutter

• Class I Antiarrhythmics (e.g., Flecainide, Propafenone):
  • Reason: These drugs can slow the atrial flutter rate without blocking conduction to the ventricles, increasing the risk of 1:1 atrioventricular (AV) conduction and dangerously high ventricular rates (e.g., 300 bpm).
  • Exception: May be used cautiously in combination with an AV nodal blocking agent (e.g., beta-blockers, calcium channel blockers) to prevent 1:1 conduction.
• Class III Antiarrhythmics (e.g., Amiodarone, Sotalol):
  • Reason: Like Class I drugs, these can slow atrial flutter rate, potentially facilitating 1:1 conduction if AV nodal conduction is intact.
  • Amiodarone Exception: May be used in specific situations but requires AV nodal blockade for safety.

Drugs to Use With Caution

• Beta-Blockers (e.g., Metoprolol, Bisoprolol):
  • Caution: Effective for rate control, but excessive doses can lead to bradycardia or hypotension, especially in combination with other rate-limiting agents.
• Non-Dihydropyridine Calcium Channel Blockers (e.g., Verapamil, Diltiazem):
  • Caution: Effective for rate control, but avoid in patients with decompensated heart failure or significant systolic dysfunction due to negative inotropic effects.

References

• Atrial Flutter, Typical and Atypical: A Review
• 2019 AHA/ACC/HRS Guidelines for Management of Atrial Arrhythmias