What is the recommended treatment to abort supraventricular tachycardia (SVT)?

Adenosine for SVT Termination

Adenosine is recommended as the first-line pharmacological treatment for acute termination of regular supraventricular tachycardia (SVT) after vagal maneuvers have been attempted. 1

Treatment Algorithm for SVT

Step 1: Initial Assessment and Vagal Maneuvers

• First determine hemodynamic stability:

  • If unstable (hypotension, altered mental status, signs of shock, ischemic chest pain): proceed directly to synchronized cardioversion 2
  • If stable: proceed with vagal maneuvers

• Vagal maneuvers as first-line intervention:

  • Valsalva maneuver: patient bears down against closed glottis for 10-30 seconds (30-40 mmHg pressure)
  • Carotid sinus massage: apply steady pressure over carotid sinus for 5-10 seconds after confirming absence of bruits
  • Success rate of vagal maneuvers is approximately 28% 2

Step 2: Adenosine Administration

• If vagal maneuvers fail, adenosine is the recommended pharmacological treatment 1
• Administration technique:
  • Rapid IV bolus via proximal IV access
  • Follow immediately with saline flush
  • Maintain continuous ECG monitoring during administration
• Dosing:
  • Initial dose: 6 mg IV push
  • If ineffective after 1-2 minutes: 12 mg IV push
  • May repeat 12 mg dose once more if needed
• Efficacy:
  • Success rates of 78-96% for AVNRT and AVRT 1
  • Highly effective (95%) for terminating AVNRT 1, 2

Step 3: Alternative Pharmacological Options

• If adenosine fails and patient remains hemodynamically stable:
  • IV beta blockers, diltiazem, or verapamil are reasonable alternatives 1, 2
  • Caution: avoid calcium channel blockers in patients with hypotension, heart failure, or pre-excited AF 2

Step 4: Synchronized Cardioversion

• Indicated when:
  • Patient is hemodynamically unstable and adenosine/vagal maneuvers fail 1, 2
  • Pharmacological therapy fails or is contraindicated in stable patients 1

Mechanism and Diagnostic Value

• Adenosine produces transient AV nodal block, disrupting reentry circuits involving the AV node 3
• Also valuable diagnostically to unmask atrial flutter or atrial tachycardia, though it rarely terminates these arrhythmias 1
• Continuous ECG recording during administration helps distinguish drug failure from immediate arrhythmia reinitiation 1

Precautions and Contraindications

• Contraindications:

  • Second or third-degree AV block (unless patient has functioning pacemaker) 4
  • Sinus node disease or symptomatic bradycardia 4
  • Bronchoconstrictive or bronchospastic lung disease (e.g., asthma) 4
  • Known hypersensitivity to adenosine 4

• Potential adverse effects:

  • Common: chest discomfort, shortness of breath, flushing (transient due to short half-life) 1, 4
  • Serious but rare: cardiac arrest, ventricular arrhythmias, myocardial infarction 4
  • Transient high-grade AV block (occurs in approximately 6% of patients) 4
  • Hypotension, particularly in patients with autonomic dysfunction or hypovolemia 4

Common Pitfalls to Avoid

• Failing to differentiate SVT from ventricular tachycardia before treatment 2
• Using verapamil or diltiazem in patients with pre-excited AF (can precipitate ventricular fibrillation) 2
• Applying pressure to eyeballs as a vagal maneuver (dangerous and abandoned) 1, 2
• Inadequate IV push technique (adenosine must be given rapidly followed by saline flush) 1
• Not having resuscitation equipment available when administering adenosine 4

Special Situations

• For refractory cases, higher doses of adenosine (up to 24-36 mg) have been used successfully in some cases 5
• Intraosseous (IO) administration is possible when IV access is difficult, particularly in pediatric patients 6
• In pregnant patients, vagal maneuvers and adenosine are preferred over other antiarrhythmic drugs 2

Adenosine's rapid metabolism and extremely short half-life (few seconds) make it particularly safe compared to other antiarrhythmic agents, even when unsuccessful in terminating the arrhythmia 3, 7.