Which medication is the first-line treatment for acute supraventricular tachycardia (SVT)?

Which medication is the first-line treatment for acute supraventricular tachycardia (SVT)?

• A. Magnesium Sulfate
• B. Adenosine
• C. Calcium Channel Blockers
• D. Lidocaine

Answer: (B)

Adenosine is the first-line treatment for acute SVT because many narrow-complex SVTs are sustained by reentry that depends on the AV node. Adenosine briefly blocks AV nodal conduction, interrupting the reentrant circuit and often terminating the tachycardia within seconds. Its ultra-short half-life means it works quickly and then wears off, minimizing ongoing effects once the rhythm is reset. Administer it as a rapid IV push followed by a saline flush. Typical steps are an initial 6 mg dose; if there’s no conversion after 1–2 minutes, a rapid 12 mg dose may be given, with a possible second dose if needed. Monitor the patient closely during and after administration for transient chest discomfort, flushing, or brief AV block; avoid if there are contraindications such as certain AV conduction diseases or significant bronchospasm risk. Other options aren’t used first-line for this scenario because they don’t work as consistently or promptly for AV node–dependent SVT. Magnesium sulfate is geared toward torsades or electrolyte-related problems, not the common SVT reentry. Calcium channel blockers can slow conduction and help some patients but have slower onset and higher risk of hypotension. Lidocaine targets ventricular arrhythmias rather than AV node–dependent SVT.

Adenosine is the first-line treatment for acute SVT because many narrow-complex SVTs are sustained by reentry that depends on the AV node. Adenosine briefly blocks AV nodal conduction, interrupting the reentrant circuit and often terminating the tachycardia within seconds. Its ultra-short half-life means it works quickly and then wears off, minimizing ongoing effects once the rhythm is reset.

Administer it as a rapid IV push followed by a saline flush. Typical steps are an initial 6 mg dose; if there’s no conversion after 1–2 minutes, a rapid 12 mg dose may be given, with a possible second dose if needed. Monitor the patient closely during and after administration for transient chest discomfort, flushing, or brief AV block; avoid if there are contraindications such as certain AV conduction diseases or significant bronchospasm risk.

Other options aren’t used first-line for this scenario because they don’t work as consistently or promptly for AV node–dependent SVT. Magnesium sulfate is geared toward torsades or electrolyte-related problems, not the common SVT reentry. Calcium channel blockers can slow conduction and help some patients but have slower onset and higher risk of hypotension. Lidocaine targets ventricular arrhythmias rather than AV node–dependent SVT.