What is the initial treatment for Atrioventricular Nodal Reentrant Tachycardia (AVNRT)?

From the Guidelines

The initial treatment for Atrioventricular Nodal Reentrant Tachycardia (AVNRT) involves vagal maneuvers followed by intravenous adenosine if necessary. Patients should first attempt vagal maneuvers such as the Valsalva maneuver (bearing down as if having a bowel movement) or carotid sinus massage, which can terminate the arrhythmia by increasing parasympathetic tone and slowing AV nodal conduction 1. If vagal maneuvers fail, adenosine should be administered intravenously, typically starting with 6 mg as a rapid bolus, followed by a saline flush. If the first dose is ineffective, a second dose of 12 mg can be given after 1-2 minutes, with a possible third dose of 12 mg if needed. Adenosine works by temporarily blocking AV nodal conduction, interrupting the reentry circuit. Patients should be warned about transient side effects including chest discomfort, flushing, and brief asystole. For hemodynamically unstable patients with AVNRT, immediate synchronized cardioversion at 50-100 joules is indicated instead. Alternative medications for stable patients include calcium channel blockers (verapamil 5-10 mg IV or diltiazem 15-20 mg IV) or beta-blockers (metoprolol 5 mg IV, repeated up to 3 doses) 1.

Some key points to consider when treating AVNRT include:

• Vagal maneuvers are recommended as the first-line treatment for AVNRT, with a success rate of approximately 27.7% 1.
• Adenosine is recommended as the second-line treatment for AVNRT, with a success rate of approximately 95% 1.
• Synchronized cardioversion is recommended for hemodynamically unstable patients with AVNRT, or for patients who do not respond to vagal maneuvers or adenosine 1.
• Calcium channel blockers and beta-blockers may be used as alternative treatments for stable patients with AVNRT, but their effectiveness may vary depending on the individual patient 1.

It's worth noting that the evidence for the treatment of AVNRT is based on guidelines from the American College of Cardiology, American Heart Association, and Heart Rhythm Society, which recommend a step-wise approach to treatment, starting with vagal maneuvers and progressing to pharmacological therapy and cardioversion as needed 1.

From the FDA Drug Label

ADENOSINE INJECTION, USP for intravenous use INDICATIONS AND USAGE Adenosine Injection, a pharmacologic stress agent, is indicated as an adjunct to thallium-201 myocardial perfusion scintigraphy in patients unable to exercise adequately ( 1) DOSAGE AND ADMINISTRATION Recommended dose is 0.14 mg/kg/min infused over six minutes as a continuous peripheral intravenous infusion (total dose of 0. 84 mg/kg) ( 2)

The initial treatment for Atrioventricular Nodal Reentrant Tachycardia (AVNRT) is adenosine (IV), with a recommended dose of 0.14 mg/kg/min infused over six minutes as a continuous peripheral intravenous infusion. 2

From the Research

Initial Treatment for Atrioventricular Nodal Reentrant Tachycardia (AVNRT)

The initial treatment for AVNRT typically involves vagal maneuvers, which are techniques used to increase parasympathetic tone, particularly useful in the management of hemodynamically stable supraventricular tachycardias 3.

Vagal Maneuvers

• Vagal maneuvers include the Valsalva maneuver, carotid sinus massage, and other techniques such as the rectal vagal maneuver 3.
• The success rate of vagal maneuvers can vary, with one study showing a success rate of 36% for vagal maneuvers compared to 84% for verapamil 4.
• Another study found that the modified Valsalva maneuver (mVM) was superior to the carotid sinus massage (CSM) maneuver in terminating SVT and maintaining rhythm, with a success rate of 43.7% for mVM compared to 9.1% for CSM 5.

Adenosine and Other Medications

• If vagal maneuvers are ineffective, adenosine can be attempted 3.
• Adenosine is a rapid-acting medication with a high conversion rate, but it can also cause negative short-term side effects such as flushing or chest discomfort 6.
• Nondihydropyridine calcium channel blockers, such as verapamil and diltiazem, may be as effective as adenosine in converting AVNRT to sinus rhythm, without the negative side effects 6.
• Beta-blockers have been evaluated but should not be used routinely due to lower efficacy 6.

Other Treatment Options

• Electrical cardioversion should be utilized for hemodynamically unstable patients 6.
• Catheter ablation is a highly effective therapy to prevent recurrence of PSVT, with single procedure success rates of 94.3% to 98.5% 7.
• Pharmacotherapy, including calcium channel blockers, β-blockers, and antiarrhythmic agents, is an important component of acute and long-term management of PSVT 7.