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Point | Counterpoint – Adenosine First-Line for SVT?

May 14, 2024

Written by Sam Parnell

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Adenosine is an effective, rapid onset, short acting atrioventricular (AV) nodal blocker that can be used as a diagnostic aid for regular narrow and wide complex tachycardias and for definitive management for supraventricular tachycardia (SVT). It should remain first-line over calcium channel blockers (CCB) for SVT.

Make new friends, but keep the old. CCBs are silver, but adenosine is gold!
Patients with stable SVT should be initially managed with vagal maneuvers, but what if that fails?  This clinical controversy article discusses the advantages of adenosine for treatment of SVT over other AV nodal blocking agents, such as CCBs and beta blockers (BB).

Adenosine’s rapid onset and short half-life (~10 seconds) make it a superb option for SVT and diagnostic tool to establish the underlying rhythm in both wide and narrow complex regular tachyarrhythmias (AVNRT, AVRT, Atrial Flutter, SVT with aberrancy, VTach, etc.).

Adenosine and CCBs both have high efficacy for termination of SVT, both with low rates of serious adverse events. However, unlike CCBs, adenosine is approved for use in most patient populations, including pregnant patients, pediatric patients, and those with congenital heart disease. CCBs also take longer to work, can be more labor intensive (i.e. slow infusion), and can cause hypotension, especially for patients with systolic heart failure. Moreover, administration of CCB to patients with atrial fibrillation with pre-excitation can lead to ventricular fibrillation and death (see Editor’s Note below). Potential drug interactions are more likely with CCB as they act on the cytochrome P450 system (though most are not clinically significant).

Caffeine is an important adenosine receptor antagonist and intake within 4 hours can reduce the efficacy of 6 mg of adenosine, so use an initial 12 mg dose of adenosine for patients with recent caffeine consumption.

Adenosine can cause initial, transient discomfort with chest tightness, shortness of breath, flushing, headache, and a “sense of impending doom”. However, these effects are fleeting, benign, and can be partially mitigated by explaining the effects to the patient before treatment.

Finally, adenosine is still recommended as first-line medical management of SVT by the American Heart Association and European Society of Cardiology guidelines.

How will this change my practice?
A wise Jedi once said, “Only a Sith deals in absolutes”, and this applies to medical management of SVT as well. Adenosine and CCBs are both important tools in my SVT toolbox. However, adenosine’s rapid onset, diagnostic utility, ease of administration, and safety in special populations outweighs the transient discomfort of administration and makes it my preferred choice for SVT.

Editor’s note added 5/14/24 12:45PM: We have gotten some comments and emails about yesterday’s post and this post. Remember, adenosine can cause severe bronchospasm. Use caution in patients with severe asthma or COPD. I have seen this go poorly! Also, any AV nodal blocker – including adenosine – is contraindicated in atrial fibrillation with preexcitation (i.e. WPW). Thanks for the comments and clarifying emails! ~Clay Smith

Adenosine Should be First-Line Treatment for Supraventricular Tachycardia. Annals of Emergency Medicine. Published December 19, 2023. doi: 10.1016/j.annemergmed.2023.10.017

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