What are the indications for adenosine?

Indications for Adenosine

Adenosine is indicated for the acute termination of hemodynamically stable paroxysmal supraventricular tachycardia (PSVT), specifically AV nodal reentrant tachycardia (AVNRT) and AV reentrant tachycardia (AVRT), and as a diagnostic agent to unmask underlying atrial arrhythmias by transiently blocking the AV node. 1

Primary Therapeutic Indications

1. Narrow-Complex Tachycardia (NCT) - First-Line Therapy

Adenosine demonstrates very high conversion rates (78-96%) for terminating regular narrow-complex tachycardias after vagal maneuvers fail 1, 2. The drug is specifically effective for:

• AV nodal reentrant tachycardia (AVNRT) - most common indication
• AV reentrant tachycardia (AVRT) - including those with accessory pathways
• Focal atrial tachycardia - particularly triggered mechanisms 3

Dosing algorithm for NCT:

• Initial dose: 6 mg rapid IV push through large peripheral vein (antecubital preferred), followed immediately by 20 mL saline flush 4, 1
• If no conversion in 1-2 minutes: 12 mg rapid IV push with saline flush
• May repeat 12 mg dose once if needed 4

Critical dose modifications:

• Reduce initial dose to 3 mg (or 1 mg) for: patients on dipyridamole or carbamazepine, heart transplant recipients, or central venous administration 4
• Increase doses may be needed for patients on theophylline, caffeine, or theobromine 4

2. Wide-Complex Tachycardia (WCT) - Diagnostic and Therapeutic Role

For stable, regular, monomorphic wide-complex tachycardia, adenosine serves dual purposes 1:

• Terminates WCT if the rhythm involves the AV node (supraventricular origin with aberrancy)
• Diagnostic tool by transiently blocking the AV node to reveal underlying atrial rhythm (e.g., atrial flutter, atrial fibrillation)
• Does not terminate ventricular tachycardia but helps differentiate it from SVT with aberrancy 5

Important caveat: A defibrillator must be immediately available, as adenosine can rarely precipitate ventricular fibrillation or profound hypotension in WCT of ventricular origin 1, 5.

3. Diagnostic Indication - Rhythm Identification

Adenosine blocks the AV node, confirming diagnoses of:

• Atrial flutter (reveals flutter waves)
• Atrial fibrillation (reveals irregular atrial activity)
• Differentiates focal AT from AVNRT/AVRT 1, 3

This transient AV block typically lasts only seconds but provides critical diagnostic information when the underlying rhythm is unclear 1.

FDA-Approved Non-Arrhythmia Indication

Pharmacologic stress testing: Adenosine 0.14 mg/kg/min infused over 6 minutes (total 0.84 mg/kg) as adjunct to thallium-201 myocardial perfusion scintigraphy in patients unable to exercise adequately 6. This indication exploits adenosine's coronary vasodilation properties to unmask flow-limiting stenoses.

Absolute Contraindications

Adenosine must never be administered in:

• Second- or third-degree AV block (without functioning pacemaker)
• Sick sinus syndrome or symptomatic bradycardia (without functioning pacemaker)
• Asthma or bronchospastic lung disease - can cause severe, life-threatening bronchospasm 4, 1, 6
• Known hypersensitivity to adenosine 6

Critical Safety Considerations

Common but transient side effects (lasting <60 seconds):

• Flushing, chest discomfort, dyspnea, sense of impending doom 4, 1
• These symptoms actually confirm adequate dosing 1

Serious adverse events (rare but potentially fatal):

• Cardiac arrest, ventricular arrhythmias, myocardial infarction 6
• Transient complete heart block (40% with 100 μg in RCA, 15% with 200 μg in LCA for intracoronary use) 7
• Cerebrovascular accidents (hemorrhagic and ischemic) 6
• New-onset or recurrent seizures 6
• Atrial fibrillation with rapid ventricular response, especially in Wolff-Parkinson-White syndrome 4

Essential monitoring: Adenosine must be administered in a monitored environment (emergency department, critical care unit) with continuous ECG recording and immediate availability of resuscitative equipment and defibrillator 5, 6.

Comparison to Alternative Agents

The 2025 AHA guidelines 1 and 2015 ACC/AHA/HRS guidelines 2 prioritize adenosine over calcium channel blockers (verapamil, diltiazem) for acute SVT termination because:

• Faster onset of action (seconds vs. minutes)
• Shorter duration of side effects (<60 seconds vs. prolonged)
• Safer in pregnancy 4
• Lower risk of hypotension compared to verapamil 1

However, calcium channel blockers or beta-blockers are preferred for recurrent SVT or when longer-acting AV nodal blockade is needed 4, 1.

Clinical Algorithm for Adenosine Use

For hemodynamically stable regular tachycardia:

1. Attempt vagal maneuvers first (modified Valsalva with passive leg raise achieves 50% conversion) 1
2. If unsuccessful → Adenosine 6 mg rapid IV push
3. If no conversion in 1-2 minutes → Adenosine 12 mg
4. If still unsuccessful → Consider calcium channel blockers or cardioversion 1

For hemodynamically unstable tachycardia:

• Proceed directly to synchronized cardioversion - do not delay for adenosine 1, 2

The evidence strongly supports adenosine as the pharmacologic agent of choice for acute SVT termination, with success rates approaching 90% when appropriately indicated and dosed 1, 2, 8.