AVNRT medical therapy
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Medical therapy can be initiated with drugs that slow AV nodal conduction:
First Line Therapy
Adenosine
Adenosine is generally considered first line therapy for AVNRT.
Treatment of AVNRT with adenosine can be complicated by:
- The development of shortness of breath due to bronchospasm
- In some cases there can be asystole which is transient given the short half life of adenosine
- Atrial fibrillation may be induced by adenosine administration
- Ventricular fibrillation is rarely induced by adenosine. When it does occur it is due to block of the AV node with rapid antegrade conduction of atrial fibrillation down the bypass tract. It is for this reason that defibrillation equipment be available.
- Adenosine should not be used in heart transplant patients
- Dipyridamole may potentiate the effect of adenosine
- Theophylline may reduce the effectiveness of adenosine
Administration:
- Place a large bore (18 gauge and larger) intravenous line
- The initial dose is 6 mg and this should be followed a saline flush with elevation of the arm to assure that the drug is infused
- If this is not effective, then 12 mg or 18 mg of adenosine can be admininistered
Beta blockers
A short acting beta-blocker such as esmolol (half life of 8 minutes) can be used to terminate an episode of AVNRT. Longer acting beta-blockers such as atenolol, metoprolol, and propranolol can also be used to reduce the risk of recurrent episodes. Atenolol may be preferable among patients with bronchospasm as it selectively blocks beta-1 receptors with little effect on beta- 2 receptors.