What are the treatment options for Supraventricular Tachycardia (SVT)?

Treatment of Supraventricular Tachycardia (SVT)

For acute SVT management, begin with vagal maneuvers (specifically the modified Valsalva maneuver in supine position with legs raised), followed immediately by adenosine 6 mg IV rapid push if vagal maneuvers fail, and proceed to synchronized cardioversion if the patient is hemodynamically unstable or medications fail. 1, 2

Acute Management Algorithm

Step 1: Vagal Maneuvers (First-Line)

• Perform the modified Valsalva maneuver as the initial intervention: patient bears down against a closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) while supine, then immediately lies flat with legs raised 1, 2
• If Valsalva fails, attempt carotid sinus massage after confirming absence of carotid bruits by auscultation—apply steady pressure over the right or left carotid sinus for 5-10 seconds 1
• Alternative vagal maneuver: apply an ice-cold, wet towel to the face to trigger the diving reflex 1, 3
• Success rate of vagal maneuvers is approximately 27.7% when switching between techniques 1
• Critical caveat: Never apply pressure to the eyeball—this practice is dangerous and abandoned 1

Step 2: Adenosine (First-Line Medication)

• Administer adenosine 6 mg rapid IV bolus through a large peripheral vein, followed immediately by saline flush 1, 2, 4
• If ineffective after 1-2 minutes, give 12 mg rapid IV bolus (may repeat once) 1, 4
• Effectiveness: 90-95% conversion rate for AVNRT and AVRT 1, 2, 3
• Essential preparation: Have resuscitative equipment immediately available, as adenosine can cause transient asystole, high-grade AV block, or precipitate atrial fibrillation 4
• Contraindications: Second- or third-degree AV block (without pacemaker), sick sinus syndrome, bronchospastic lung disease (asthma), and known hypersensitivity 4
• Warning: Fatal cardiac arrest, sustained ventricular tachycardia, and myocardial infarction have occurred—avoid in patients with acute myocardial ischemia or unstable angina 4

Step 3: Alternative Medications (If Adenosine Fails or Contraindicated)

• For hemodynamically stable patients, use IV calcium channel blockers or beta-blockers 1, 2:
  • IV diltiazem or verapamil are particularly effective for AVNRT conversion (80-98% success rate) 1
  • IV beta-blockers (e.g., metoprolol, esmolol) are reasonable alternatives, though less effective than calcium channel blockers 1
• Critical warning: Do NOT give verapamil or diltiazem if ventricular tachycardia or pre-excited atrial fibrillation is suspected—this can cause hemodynamic collapse or ventricular fibrillation 1, 3
• Avoid calcium channel blockers in patients with suspected systolic heart failure 1

Step 4: Synchronized Cardioversion

• For hemodynamically unstable patients: Perform immediate synchronized cardioversion when vagal maneuvers and adenosine fail or are not feasible 1
• For hemodynamically stable patients: Use synchronized cardioversion when pharmacological therapy fails or is contraindicated 1
• Initial energy: 50-100 joules for SVT 3
• Safety note: Synchronized cardioversion is safe and effective in all trimesters of pregnancy if necessary 1, 5

Long-Term Management

Pharmacological Prevention

• Beta-blockers are the first-line option for long-term prevention of recurrent SVT 2, 6
• Calcium channel blockers (diltiazem or verapamil) are reasonable alternatives to beta-blockers 2
• Important caveat: When discontinuing beta-blockers in patients with coronary artery disease, taper gradually over 1-2 weeks to avoid severe exacerbation of angina, myocardial infarction, or ventricular arrhythmias 6

Catheter Ablation (Curative Option)

• Catheter ablation is the definitive curative treatment for patients with 2, 7:
  • Frequent symptomatic episodes
  • Poor tolerance or ineffectiveness of medications
  • Patient preference for non-pharmacological approach
• Ablation is curative in the majority of patients and should be discussed with all patients after initial SVT episode 7

Special Populations

Pregnancy

• Vagal maneuvers remain first-line and are safe during pregnancy 1, 5
• Adenosine is safe due to its extremely short half-life (unlikely to reach fetal circulation) 1, 5
• Avoid atenolol and verapamil for long-term management due to teratogenic effects 5
• Synchronized cardioversion can be performed safely at all stages of pregnancy if necessary 1

Pre-Excitation Syndromes (e.g., Wolff-Parkinson-White)

• Avoid all AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers, digoxin) in pre-excited atrial fibrillation—these can accelerate ventricular rate and cause hemodynamic collapse 1, 3
• Use IV procainamide or ibutilide for hemodynamically stable pre-excited AF 2
• Use immediate cardioversion for hemodynamically unstable patients 8

Patients with Low Baseline Heart Rate

• Vagal maneuvers remain safe as first-line treatment 3
• Reduce adenosine dosing and monitor carefully for prolonged bradycardia 3
• Consider synchronized cardioversion earlier in the treatment algorithm, as these patients may not tolerate rate-controlling medications 3
• Avoid high doses of AV nodal blocking agents (beta-blockers, calcium channel blockers) as they may exacerbate underlying bradycardia 3

Critical Diagnostic Considerations

• Always obtain a 12-lead ECG during tachycardia before treatment to differentiate SVT mechanisms 2
• Distinguish SVT with aberrancy from ventricular tachycardia before initiating treatment—giving calcium channel blockers or beta-blockers for VT can be fatal 1, 2
• Rule out organic heart disease (especially mitral stenosis from rheumatic heart disease) in patients presenting with SVT 5

Common Pitfalls to Avoid

• Never abruptly discontinue beta-blocker therapy in patients with coronary artery disease—this can precipitate severe angina, MI, or ventricular arrhythmias 6
• Do not use calcium channel blockers or beta-blockers if pre-excited AF or VT is suspected 1, 3
• Prepare for atrial fibrillation when giving adenosine—it may precipitate AF requiring cardioversion 3, 4
• Automatic tachycardias (ectopic atrial tachycardia, multifocal atrial tachycardia) will not respond to cardioversion and require different treatment approaches 3
• Beta-blockers may mask hypoglycemia in diabetic patients (tachycardia will be blunted, though dizziness and sweating persist) 6