What are the treatment options for a patient with atrioventricular reentrant tachycardia (AVRT)?

Treatment of Atrioventricular Reentrant Tachycardia (AVRT)

For hemodynamically stable patients with AVRT, begin with vagal maneuvers (particularly the modified Valsalva technique), followed immediately by adenosine if unsuccessful, then proceed to IV calcium channel blockers or beta blockers as third-line therapy; for hemodynamically unstable patients, perform immediate synchronized cardioversion without delay. 1, 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

• Hemodynamically unstable patients (hypotension with altered mental status, signs of shock, acute heart failure, pulmonary edema, or ongoing chest pain) require immediate synchronized cardioversion as the definitive first-line treatment 1, 3
• Do not delay cardioversion to attempt vagal maneuvers or pharmacological therapy in truly unstable patients 3

Step 2: Treatment for Hemodynamically Stable Patients

First-Line: Vagal Maneuvers (Class I Recommendation)

• Modified Valsalva maneuver is 2.8-3.8 times more effective than standard technique and should be attempted first 2
• Position the patient supine before beginning 1, 2
• Patient should bear down against a closed glottis for 10-30 seconds, generating intrathoracic pressure of at least 30-40 mmHg 1, 2
• Alternative vagal maneuvers include carotid sinus massage (after confirming absence of carotid bruits by auscultation, apply steady pressure for 5-10 seconds) or applying an ice-cold wet towel to the face 1, 2
• Vagal maneuvers achieve approximately 27.7% success rate when switching between techniques 1

Second-Line: Adenosine (Class I Recommendation)

• Adenosine terminates orthodromic AVRT in 90-95% of patients and is the drug of choice for acute management 1, 2, 4, 5
• Administer as 6 mg rapid IV push through a large vein, followed immediately by saline flush 2
• If unsuccessful, give up to two subsequent doses of 12 mg 2
• Critical safety consideration: Have cardioversion equipment immediately available, as adenosine may precipitate atrial fibrillation that can conduct rapidly down the accessory pathway, potentially causing ventricular fibrillation 1, 6
• Minor side effects (flushing, chest discomfort, shortness of breath) occur in approximately 30% of patients but last less than 1 minute 1, 6
• Atrial or ventricular premature complexes may occur immediately after conversion, potentially retriggering AVRT 1, 2

Third-Line: IV Calcium Channel Blockers or Beta Blockers (Class IIa Recommendation)

• IV diltiazem, verapamil, or beta blockers achieve 80-98% success rates when adenosine fails 1, 2
• These agents are reasonable for acute treatment in hemodynamically stable patients 1

Fourth-Line: Synchronized Cardioversion

• Perform synchronized cardioversion when pharmacological therapy is ineffective or contraindicated in hemodynamically stable patients (Class I recommendation) 1
• Use 50-100J initial energy for SVT 2

Critical Pitfalls to Avoid

Pre-Excited Atrial Fibrillation

• Never use AV nodal blocking agents (adenosine, verapamil, diltiazem, beta blockers) in patients with manifest accessory pathways who develop atrial fibrillation 1, 2
• These agents may be contraindicated in patients at risk of rapid conduction down the accessory pathway during AF 1
• Immediate synchronized cardioversion is mandatory for pre-excited AF 1, 2
• Alternative pharmacological options for hemodynamically stable pre-excited AF include IV ibutilide or procainamide (Class I recommendation) 1

Distinguishing AVRT from Other Arrhythmias

• Ensure the rhythm is truly AVRT before administering verapamil or diltiazem, as these can be dangerous in ventricular tachycardia or pre-excited AF 3, 7
• Adenosine can serve as both a therapeutic and diagnostic agent, unmasking atrial activity in other arrhythmias 1, 5

Long-Term Management

Definitive Treatment: Catheter Ablation (Class I Recommendation)

• Catheter ablation targeting the accessory pathway is the definitive treatment with high success rates 1, 5, 8
• This is the preferred treatment in patients with symptomatic AVRT requiring long-term management 1, 5
• Ablation has revolutionized management with high efficacy and low complication rates 5, 9, 10

Pharmacological Prevention (for patients who decline or are not candidates for ablation)

Treatment can target either the AV node or the accessory pathway:

AV Nodal Blocking Agents:

• Oral beta blockers are the preferred first-line drugs for chronic management (Class I recommendation) 1, 4
• Oral verapamil or diltiazem are reasonable alternatives (Class IIa recommendation) 1, 4
• These agents should be avoided in patients with severe conduction abnormalities or sinus node dysfunction 1, 3

Accessory Pathway Blocking Agents:

• Flecainide or propafenone can be effective for ongoing management in patients without structural heart disease or ischemic heart disease (Class IIa recommendation) 1, 11, 4
• These agents should be avoided in patients with structurally abnormal hearts due to higher risk of proarrhythmia 11, 4
• Initiation should occur in an inpatient setting to monitor for proarrhythmias 4

Agents Affecting Both:

• Sotalol or amiodarone may be reasonable for resistant cases (Class IIb recommendation) 1, 4
• These are typically reserved for patients who fail other therapies 4, 5

Special Populations

Pediatric Patients

• Adenosine remains the drug of choice for acute management in hemodynamically stable children 4
• Beta blockers are preferred for chronic management in infants and small children, as catheter ablation carries higher risk in this population 4
• Verapamil should be avoided in infants and patients with decreased cardiac function 4

Pregnant Patients

• Vagal maneuvers remain first-line 2
• Adenosine is safe and recommended as first-line pharmacologic therapy 2
• Synchronized cardioversion is safe at all stages of pregnancy when pharmacologic therapy fails 2