Management of Supraventricular Tachycardia
Immediate Assessment: Hemodynamic Stability
The first and most critical decision is determining hemodynamic stability—if the patient shows hypotension, signs of shock, altered mental status, chest pain, acute heart failure, or respiratory compromise, proceed immediately to synchronized cardioversion without attempting vagal maneuvers or medications. 1, 2
- Hemodynamically unstable patients require immediate synchronized cardioversion at 50-100 J (biphasic) as the definitive treatment 2
- Do not delay cardioversion for any other intervention in unstable patients 2, 3
Management of Hemodynamically Stable SVT
Step 1: Vagal Maneuvers (First-Line)
Vagal maneuvers are Class I, Level B evidence and should be attempted first in all stable patients. 1, 2
- Modified Valsalva maneuver is most effective: patient bears down against closed glottis for 10-30 seconds (generating 30-40 mm Hg pressure) while supine, then immediately lies flat with legs elevated 1, 2
- Carotid sinus massage: Apply steady pressure over right or left carotid sinus for 5-10 seconds after confirming absence of bruit by auscultation 1
- Ice-cold towel to face or facial immersion in 10°C water activates diving reflex 1
- Success rate approximately 27.7% when switching between techniques 1
- Never apply pressure to eyeballs—this is dangerous and abandoned 1
Step 2: Adenosine (Second-Line)
If vagal maneuvers fail, adenosine is the next intervention with 90-95% effectiveness for terminating AVNRT and orthodromic AVRT. 1, 2
- Dosing: 6 mg rapid IV push through large peripheral vein, followed immediately by 20 mL saline flush 2
- If ineffective, give 12 mg, then another 12 mg if needed 1
- Dose adjustments: Reduce to 3 mg for patients on dipyridamole, carbamazepine, or with transplanted hearts; larger doses needed with theophylline or caffeine 2
- Contraindications: Severe asthma (can cause severe bronchoconstriction) 2
- Always have resuscitation equipment immediately available 2
Step 3: Alternative Pharmacologic Agents
If adenosine fails or is contraindicated:
- Beta-blockers (metoprolol) or non-dihydropyridine calcium channel blockers (verapamil, diltiazem) are reasonable alternatives 1
- Verapamil has advantage of not exacerbating pulmonary disease 1
Step 4: Synchronized Cardioversion
If pharmacologic therapy fails or is contraindicated in stable patients, proceed to synchronized cardioversion with adequate sedation/anesthesia. 1, 2
Critical Safety Warnings
Absolute Contraindications to AV Nodal Blocking Agents
Never use verapamil, diltiazem, or other AV nodal blocking agents in:
- Wide-complex tachycardia of uncertain etiology—may be ventricular tachycardia and these agents can cause hemodynamic collapse 1, 2
- Pre-excited atrial fibrillation (Wolff-Parkinson-White with AF)—can precipitate ventricular fibrillation by accelerating ventricular rate 1, 2, 3
- Severe systolic heart failure—risk of hemodynamic collapse 2
Wide-Complex Tachycardia Pitfall
- If QRS duration >120 ms, treat as ventricular tachycardia until proven otherwise 1, 3
- Administration of verapamil or diltiazem for VT can lead to hemodynamic compromise or ventricular fibrillation 1
- The presence of previous myocardial infarction strongly indicates VT 1
Special Considerations
Automatic Tachycardias (Non-Reentrant)
- Multifocal atrial tachycardia, ectopic atrial tachycardia, and junctional tachycardia do not respond to cardioversion 2
- These require rate control with AV nodal blocking agents (verapamil, diltiazem, or metoprolol) rather than rhythm control 1, 2
- Verapamil or diltiazem preferred for MAT in patients with pulmonary disease 1
Long-Term Management
- All patients treated for SVT should be referred to a heart rhythm specialist 4
- Catheter ablation is first-line for long-term management of recurrent, symptomatic paroxysmal SVT with high success rates 5, 4
- Beta-blockers or calcium channel blockers may be used for chronic suppressive therapy if ablation is declined or not feasible 5, 4