What is the initial management for a patient presenting with supraventricular arrhythmia?

Initial Management of Supraventricular Arrhythmia

The initial management of supraventricular arrhythmia should include immediate 12-lead ECG recording (if hemodynamically stable) or immediate DC cardioversion (if hemodynamically unstable), followed by vagal maneuvers and/or intravenous adenosine for stable narrow-complex tachycardias. 1

Assessment and Diagnosis

Immediate Evaluation

1. Assess hemodynamic stability

   • Check for signs of shock, hypotension, altered mental status, chest pain, or heart failure
   • Obtain vital signs including blood pressure and heart rate

2. Obtain ECG documentation

   • 12-lead ECG during tachycardia (if patient is stable)
   • At minimum, obtain a monitor strip before any intervention 1
   • Determine if QRS is narrow (<120 ms) or wide (≥120 ms)

Differential Diagnosis

• Narrow QRS complex (<120 ms): Almost always supraventricular

  • AVNRT (AV nodal reentrant tachycardia) - most common if regular with no visible P waves
  • AVRT (AV reciprocating tachycardia) - likely if P wave visible in ST segment
  • Atrial tachycardia
  • Atrial flutter
  • Atrial fibrillation

• Wide QRS complex (≥120 ms): Could be SVT with aberrancy or ventricular tachycardia

  • If uncertain, treat as ventricular tachycardia 1

Management Algorithm

For Hemodynamically Unstable Patients

1. Immediate synchronized DC cardioversion regardless of QRS width 1
   • Use lower energy (50 joules) for atrial flutter
   • Higher energy may be needed for other SVTs

For Hemodynamically Stable Patients with Narrow QRS

1. Vagal maneuvers (first-line)

   • Valsalva maneuver
   • Carotid sinus massage (if appropriate)
   • Record 12-lead ECG during maneuvers if possible

2. IV Adenosine (if vagal maneuvers fail)

   • Initial dose: 6 mg rapid IV push followed by saline flush
   • If ineffective, give 12 mg IV push (can repeat once if needed)
   • Contraindicated in severe asthma
   • Use with caution in patients on theophylline (may need higher doses)
   • Effects potentiated by dipyridamole
   • Higher rates of heart block may occur with concomitant carbamazepine 1

3. IV Calcium-channel blockers or beta blockers (if adenosine fails or is contraindicated)

   • Verapamil or diltiazem
   • Metoprolol
   • Avoid combining IV calcium-channel blockers with beta blockers due to risk of hypotension/bradycardia 1

For Hemodynamically Stable Patients with Wide QRS

1. If definitely SVT with aberrancy: Treat as narrow QRS SVT
2. If uncertain origin: Treat as ventricular tachycardia
   • IV procainamide or sotalol (if stable)
   • Amiodarone (preferred in patients with impaired LV function or heart failure) 1

Special Considerations

Pre-excited SVT (WPW Syndrome)

• Avoid adenosine, calcium-channel blockers, and digoxin
• These can accelerate conduction through accessory pathway in atrial fibrillation
• DC cardioversion is preferred for irregular wide-complex tachycardias 1

Post-conversion Management

• Identify and eliminate precipitating factors:

  • Caffeine, alcohol, nicotine
  • Recreational drugs
  • Hyperthyroidism
  • Electrolyte abnormalities

• Consider empiric beta-blocker if symptoms are significant and bradycardia (<50 bpm) has been excluded 1

Additional Investigations After Stabilization

• Echocardiogram to exclude structural heart disease
• Consider 24-hour Holter monitoring for frequent episodes
• Event recorder for less frequent episodes
• Exercise testing if arrhythmia is exertion-triggered 1

Indications for Specialist Referral

• All patients with WPW syndrome
• Wide complex tachycardia of unknown origin
• Drug resistance or intolerance
• Patients desiring to be free of drug therapy
• Severe symptoms (syncope, dyspnea) during palpitations 1

Remember that the most effective and rapid means of terminating any hemodynamically unstable tachycardia is DC cardioversion, which should not be delayed for diagnostic procedures in unstable patients.