What is the mechanism of action of adenosine for supraventricular tachycardia (SVT)?

From the Guidelines

Adenosine is the recommended treatment for supraventricular tachycardia (SVT) due to its effectiveness in terminating the arrhythmia by temporarily blocking electrical conduction through the atrioventricular (AV) node, with a success rate ranging from 78% to 96% 1.

Mechanism of Action

Adenosine works by activating adenosine receptors that increase potassium conductance and hyperpolarize cardiac cells, making them less excitable and temporarily interrupting the tachycardia circuit. This mechanism allows adenosine to effectively terminate SVT that is due to either AVNRT or AVRT.

Administration and Dosage

The standard dosing of adenosine begins with 6 mg given as a rapid intravenous push, followed by a saline flush. If the first dose is ineffective, a second dose of 12 mg can be administered after 1-2 minutes, and a third dose of 12 mg can be given if necessary 1. It is essential to administer adenosine via proximal IV as a rapid bolus infusion followed by a saline flush.

Side Effects and Contraindications

Patients should be warned about transient symptoms including chest pressure, flushing, shortness of breath, and a sense of impending doom, which typically resolve within seconds. Adenosine is contraindicated in patients with severe asthma, second or third-degree heart block without a pacemaker, and those taking dipyridamole or carbamazepine 1.

Key Points

• Adenosine is effective in terminating SVT with a success rate ranging from 78% to 96% 1.
• The medication has an extremely short half-life of less than 10 seconds, which minimizes side effects but necessitates rapid administration.
• Adenosine should be administered in a monitored environment, such as a critical care unit or accident and emergency department, as it can cause transient complete heart block 1.

From the FDA Drug Label

Adenosine produces a direct negative chronotropic, dromotropic and inotropic effect on the heart, presumably due to A1-receptor agonism, and produces peripheral vasodilation, presumably due to A2-receptor agonism

• Mechanism of Action: Adenosine works for supraventricular tachycardia (SVT) by activating purine receptors (cell-surface A1 and A2 adenosine receptors), which leads to:

• Negative chronotropic effect (decreases heart rate)
• Negative dromotropic effect (decreases conduction velocity)
• Negative inotropic effect (decreases contractility)

• Key Effect: The activation of A1 receptors is thought to be responsible for the therapeutic effect of adenosine in SVT, by slowing the heart rate and increasing the refractoriness of the AV node 2

From the Research

Mechanism of Adenosine in SVT

• Adenosine works by causing a transient heart block, which can help terminate supraventricular tachycardia (SVT) that is dependent on the atrioventricular (AV) node 3, 4.
• The use of adenosine is recommended as a first-line therapy in the acute diagnosis and management of SVT, according to recent European Society of Cardiology guidelines 3.
• Adenosine is effective in treating SVT because it can slow down or block the electrical conduction between the atria and ventricles, thereby interrupting the reentrant circuit that maintains the tachycardia 4, 5.

Administration and Dosage

• The standard dosing regimen for adenosine is 6 mg, 12 mg, and 12 mg, administered intravenously 4, 5.
• However, in cases where the standard dosing regimen fails to terminate SVT, higher doses of adenosine (up to 24 mg or 36 mg) may be considered, in consultation with a cardiologist 5.
• The administration of adenosine should be done under close monitoring, with continuous electrocardiogram (ECG) recording and rhythm strip analysis 4, 5.

Efficacy and Safety

• Adenosine is generally safe and effective in treating SVT, with a high success rate in terminating the arrhythmia 3, 4, 6.
• However, adenosine may not be effective in all cases of SVT, and alternative therapies such as beta blockers, calcium channel blockers, or catheter ablation may be necessary 3, 7, 6.
• The use of adenosine should be carefully considered in patients with certain underlying medical conditions, such as heart failure or atrioventricular block 4, 6.