When is adenosine administered during cardiac issues, specifically supraventricular tachycardia (SVT)?

From the Guidelines

Adenosine is administered during specific cardiac emergencies, primarily to treat paroxysmal supraventricular tachycardia (PSVT), and is recommended for acute treatment in patients with regular SVT, including AVNRT and AVRT, with a success rate of 90% to 95% 1. The standard dosing protocol begins with 6 mg given as a rapid intravenous bolus over 1-2 seconds, followed by a saline flush. If the first dose is ineffective after 1-2 minutes, a 12 mg dose can be administered, with a possible third dose of 12 mg if needed.

Key Considerations

• Adenosine works by temporarily blocking electrical conduction through the AV node, interrupting the reentry circuit that maintains PSVT and allowing the heart to reset to normal sinus rhythm.
• The medication has an extremely short half-life of less than 10 seconds, which makes it ideal for emergency use as any side effects quickly resolve.
• Patients should be warned about transient symptoms including chest pressure, flushing, shortness of breath, and a brief period of asystole that may occur during administration.
• Adenosine is contraindicated in patients with second or third-degree heart block, sick sinus syndrome without a pacemaker, and those with known hypersensitivity to the drug.
• It should be used with caution in patients with asthma due to potential bronchospasm.

Administration Guidelines

• Adenosine should be administered via proximal IV as a rapid bolus infusion followed by a saline flush.
• Continuous ECG recording during adenosine administration may help diagnostically and can also distinguish drug failure due to failure to terminate the arrhythmias versus successful termination with immediate arrhythmia reinitiation 1.

Clinical Context

• Vagal maneuvers, including Valsalva and carotid sinus massage, are recommended as the first-line intervention to terminate SVT, but adenosine is beneficial when these maneuvers are ineffective or not feasible 1.
• Synchronized cardioversion is recommended for acute treatment in patients with hemodynamically unstable SVT when vagal maneuvers or adenosine are ineffective or not feasible 1.

From the Research

Administration of Adenosine in Heart Issues

• Adenosine is administered during heart issues such as paroxysmal supraventricular tachycardia (PSVT) to convert the arrhythmia to sinus rhythm 2, 3, 4.
• The typical dose of adenosine for PSVT is 6-12 mg, administered as a rapid intravenous bolus 2, 3.
• If the initial dose is ineffective, additional doses of 12 mg can be administered until the arrhythmia is terminated 2, 3.
• In some cases, higher doses of adenosine (up to 36 mg) may be necessary to terminate the arrhythmia 5.

Timing of Adenosine Administration

• Adenosine can be administered at any time during the treatment of PSVT, but it is most effective when administered early in the course of the arrhythmia 3, 4.
• Adenosine can also be used to induce coronary vasodilation in patients undergoing diagnostic procedures such as thallium-201 single photon emission computed tomography (201Tl SPECT) or positron emission tomography (PET) 2.

Comparison with Other Treatments

• Adenosine has been compared to other treatments for PSVT, including calcium channel antagonists (CCAs) 6.
• Studies have shown that adenosine and CCAs are equally effective in terminating PSVT, but adenosine may have a faster onset of action and fewer side effects 6.
• However, the choice of treatment ultimately depends on the individual patient's condition and medical history 4, 6.