What is Atrioventricular Nodal Reentrant Tachycardia (AVNRT), its diagnosis, treatment, and maintenance medications?

From the Guidelines

Atrioventricular nodal reentrant tachycardia (AVNRT) is a common type of supraventricular tachycardia that can be diagnosed with an ECG and treated with vagal maneuvers, adenosine, or catheter ablation, with a focus on improving quality of life and reducing morbidity and mortality. AVNRT is caused by an abnormal electrical circuit within the AV node that creates a reentry loop, resulting in a narrow-complex tachycardia with heart rates of 140-250 beats per minute and often "pseudo-S waves" in inferior leads or "pseudo-R prime" in lead V1 1.

Diagnosis and Acute Treatment

Diagnosis typically involves documenting the arrhythmia with an ECG during symptoms. Acute treatment includes:

• Vagal maneuvers like the Valsalva maneuver or carotid sinus massage as first-line interventions 1
• Intravenous adenosine (6mg rapid push, followed by 12mg if needed) as the medication of choice to terminate an acute episode 1
• Synchronized cardioversion for hemodynamically unstable patients or those who do not respond to adenosine or vagal maneuvers 1

Long-term Management

For long-term management, catheter ablation is considered the definitive treatment with a success rate over 95% and low complication risk 1. For those who cannot undergo ablation or prefer medication, options include:

• Beta-blockers (metoprolol 25-100mg twice daily) 1
• Calcium channel blockers (diltiazem 120-360mg daily or verapamil 120-360mg daily) 1
• Class IC antiarrhythmics like flecainide (50-200mg twice daily) for those without structural heart disease 1

Lifestyle Modifications and Follow-up

Patients living with AVNRT should:

• Avoid triggers like excessive caffeine, alcohol, and stress when possible
• Stay well-hydrated
• Learn to perform vagal maneuvers correctly
• Regular follow-up with a cardiologist is important to monitor medication effectiveness and adjust treatment as needed 1

Quality of Life and Prognosis

The condition is generally benign but can significantly impact quality of life due to symptoms like palpitations, dizziness, shortness of breath, and anxiety during episodes. With proper treatment and management, patients with AVNRT can lead normal lives with minimal symptoms and improved quality of life 1.

From the FDA Drug Label

In patients without structural heart disease, flecainide acetate tablets, USP are indicated for the prevention of: •paroxysmal supraventricular tachycardias (PSVT), including atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia and other supraventricular tachycardias of unspecified mechanism associated with disabling symptoms

AVNRT Definition and Diagnosis: Atrioventricular Nodal Reentrant Tachycardia (AVNRT) is a type of supraventricular tachycardia. The diagnosis of AVNRT is typically made based on symptoms and electrocardiogram (ECG) findings, but the provided drug labels do not directly address the diagnostic process.

Treatment and Maintenance:

• Flecainide: may be used for the prevention of paroxysmal supraventricular tachycardias (PSVT), including AVNRT, in patients without structural heart disease 2.
• Adenosine: is not directly indicated for the treatment of AVNRT, but it can be used for diagnostic purposes in certain cardiac conditions 3.

Note: The provided drug labels do not offer comprehensive information on the diagnosis, treatment, and maintenance of AVNRT.

From the Research

What is AVNRT

• Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of regular narrow complex tachycardia 4
• It is due to dual atrioventricular nodal conduction over two pathways with different electrophysiological properties 4
• The first pathway ('fast' pathway) conducts faster but has longer refractory period than the second pathway ('slow' pathway) 4

Diagnosis of AVNRT

• Clinically, AVNRT patients usually have palpitations in their neck during attacks 4
• On the surface electrocardiogram, the diagnosis is suggested by the absence of P waves during tachycardia or very discrete P waves immediately after the QRS or an rSr' pattern in lead VI 4
• Electrophysiologically, it can be reproducibly initiated or terminated by cardiac pacing 4
• A Holter monitor or event recorder may be needed to confirm the diagnosis 5

Treatment of AVNRT

• Acute termination of tachycardia can be achieved by vagal manoeuvres or drugs 4
• Adenosine compounds are excellent drugs, as are calcium channel blockers, for acute termination of the arrhythmia 4
• Vagal maneuvers, such as the Valsalva maneuver, can terminate the arrhythmia 6
• A rectal thermometer can be used as an alternative vagal maneuver to convert AVNRT into sinus rhythm 7
• If chronic therapy is indicated, digitalis, calcium blockers and beta-blockers are effective and simple initial options 4
• Catheter ablation, especially using radiofrequency energy, antitachycardia pacing and surgery are therapeutic alternatives for the resistant patient 4
• Radiofrequency catheter ablation (RFA) has been used increasingly in children as treatment for AVNRT 8
• Catheter ablation has a success rate of 95% and recurrence rate of less than 5%, and causes inadvertent heart block in less than 1% of patients 5

Maintenance Drugs

• Calcium channel blockers (diltiazem or verapamil) or beta blockers (metoprolol) can be used acutely or as long-term therapy 5
• Class Ic antiarrhythmics (flecainide or propafenone) can be used long-term 5
• Class Ia antiarrhythmics (quinidine, procainamide, or disopyramide) are used less often because of their modest effectiveness and adverse effects 5
• Class III antiarrhythmics (amiodarone, sotalol, or dofetilide) are effective, but have potential adverse effects and should be administered in consultation with a cardiologist 5