What is the initial treatment for a patient with Atrioventricular Reentrant Tachycardia (AVRT)?

Initial Treatment for Atrioventricular Reentrant Tachycardia (AVRT)

Begin with vagal maneuvers immediately as first-line treatment, followed by adenosine if vagal maneuvers fail, and proceed to synchronized cardioversion for hemodynamically unstable patients or when pharmacological therapy is ineffective. 1

Treatment Algorithm for Hemodynamically Stable Patients

First-Line: Vagal Maneuvers

• Perform the modified Valsalva maneuver with the patient in the supine position, which is 2.8-3.8 times more effective than the standard technique 2
• The patient should bear down against a closed glottis for 10-30 seconds, generating intrathoracic pressure of at least 30-40 mmHg 1
• Alternative vagal maneuvers include carotid sinus massage (after confirming absence of carotid bruits by auscultation, applying steady pressure for 5-10 seconds) or applying an ice-cold wet towel to the face 1
• Valsalva maneuver combined with carotid sinus massage achieves an overall success rate of 27.7% when switching between techniques 1

Second-Line: Adenosine

• Adenosine is effective for conversion of orthodromic AVRT in 90-95% of patients 1, 3
• Administer 6 mg as a rapid IV push through a large vein, followed immediately by saline flush 2
• If unsuccessful, give 12 mg doses (up to two additional doses) 4
• Critical safety consideration: Have electrical cardioversion equipment immediately available, as adenosine may precipitate atrial fibrillation that can conduct rapidly to the ventricle and potentially cause ventricular fibrillation 1
• Minor side effects occur in approximately 30% of patients but last less than 1 minute 1

Third-Line: IV Calcium Channel Blockers or Beta Blockers

• IV verapamil or diltiazem achieve 80-98% success rates in resistant cases 2, 3
• Verapamil initial dose is 0.075-0.1 mg/kg, with subsequent 5 mg boluses up to a maximum of 15-20 mg 3
• These agents are only appropriate for hemodynamically stable patients 5

Treatment for Hemodynamically Unstable Patients

Immediate Synchronized Cardioversion

• Perform immediate synchronized cardioversion without delay if the patient demonstrates hypotension with altered mental status, signs of shock, acute heart failure, pulmonary edema, or ongoing chest pain 1, 5
• Synchronized cardioversion is highly effective in terminating AVRT and avoids complications associated with antiarrhythmic drug therapy 1
• Use 50-100J initial energy for SVT 2
• Do not delay cardioversion to attempt vagal maneuvers or adenosine if the patient is truly unstable 5

Critical Pitfalls to Avoid

Pre-Excited Atrial Fibrillation

• Never administer AV nodal blocking agents (verapamil, diltiazem, digoxin, or beta blockers) to patients with pre-excited AF, as these may enhance accessory pathway conduction and lead to ventricular fibrillation 1, 3, 6
• For hemodynamically unstable pre-excited AF, perform immediate synchronized cardioversion 1
• For hemodynamically stable pre-excited AF, use ibutilide or IV procainamide 1, 6

Post-Conversion Management

• Atrial or ventricular premature complexes may occur immediately after conversion (whether from adenosine or cardioversion) and may reinitiate AVRT 1
• An antiarrhythmic drug may be required to prevent acute reinitiation of tachycardia 1, 2

Contraindications to Specific Therapies

• Avoid verapamil in infants and patients with decreased cardiac function 7
• Beta blockers should be avoided in patients with severe conduction abnormalities or sinus node dysfunction 5
• Confirm the rhythm is truly AVRT before administering AV nodal blocking agents, as these can be dangerous in ventricular tachycardia 5