What is the treatment approach for supraventricular tachycardia (SVT)?

Treatment of Supraventricular Tachycardia (SVT)

For hemodynamically stable SVT, begin with vagal maneuvers followed immediately by adenosine 6-12 mg IV if unsuccessful, then proceed to IV calcium channel blockers or beta blockers if adenosine fails; for hemodynamically unstable patients, perform immediate synchronized cardioversion. 1, 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

Determine if the patient shows any signs of instability: hypotension, altered mental status, signs of shock, chest pain, or acute heart failure symptoms. 1, 2

• If hemodynamically unstable: Proceed immediately to synchronized cardioversion (see below). 1, 2
• If hemodynamically stable: Continue with stepwise approach below. 1, 2

Step 2: Hemodynamically Stable Patients

First-Line: Vagal Maneuvers

• Attempt vagal maneuvers first, with the modified Valsalva maneuver being most effective (overall success rate approximately 27.7%). 3, 2
• Record a 12-lead ECG during tachycardia before attempting conversion to aid in diagnosis. 3

Second-Line: Adenosine

• If vagal maneuvers fail, administer adenosine 6 mg IV rapid push, followed by 12 mg if needed. 3, 2
• Adenosine has a 90-95% success rate for terminating AVNRT and orthodromic AVRT. 3, 2
• Expect brief side effects in approximately 30% of patients (flushing, chest discomfort, dyspnea). 2
• Critical caveat: Adenosine may precipitate atrial fibrillation and should be used with caution if pre-excited AF is suspected. 3

Third-Line: Calcium Channel Blockers or Beta Blockers

• If adenosine fails or recurs after conversion, use IV diltiazem or verapamil. 1
• These agents terminate SVT in 64-98% of patients. 1
• Administer slowly over up to 20 minutes to minimize hypotension risk. 1
• Alternative: IV beta blockers (such as esmolol) are reasonable with an excellent safety profile, though slightly less effective than diltiazem. 1, 4
• Esmolol maintenance doses of 50-200 mcg/kg/min are effective, with about 60-70% of patients achieving heart rate control. 4

Fourth-Line: Synchronized Cardioversion

• If pharmacological therapy is ineffective or contraindicated in stable patients, perform synchronized cardioversion after adequate sedation. 1

Step 3: Hemodynamically Unstable Patients

Perform immediate synchronized cardioversion. 1, 2

• This is highly effective and successfully restores sinus rhythm in all patients when performed promptly. 1
• Exception: If the tachycardia is regular with narrow QRS complex, consider adenosine first even in unstable patients, but do not delay cardioversion if adenosine is unavailable or fails immediately. 1

Critical Warnings and Pitfalls

Pre-Excited Atrial Fibrillation

• Never use AV nodal blocking agents (adenosine, diltiazem, verapamil, beta-blockers) in pre-excited AF, as these may accelerate ventricular rate and precipitate ventricular fibrillation. 3
• For hemodynamically stable pre-excited AF, use ibutilide or IV procainamide instead. 3, 2
• For hemodynamically unstable pre-excited AF, synchronized cardioversion is mandatory. 3

Ventricular Tachycardia Mimics

• Do not give verapamil or diltiazem if you cannot definitively exclude VT, as this may cause hemodynamic collapse. 3
• Ensure QRS duration is assessed; if >120 ms, distinguish VT from SVT with aberrancy before administering AV nodal blockers. 3

Heart Failure Contraindications

• Diltiazem and verapamil are not appropriate for patients with suspected systolic heart failure. 1

Long-Term Management

First-Line: Catheter Ablation

Catheter ablation is the most effective therapy to prevent recurrent SVT and should be offered as first-line treatment for symptomatic patients. 1, 2

• Success rates are 94.3-98.5% with a single procedure. 2
• This provides definitive cure without need for chronic pharmacological therapy. 1

Alternative: Pharmacological Therapy

For patients who decline ablation or are not candidates:

• Oral beta blockers, diltiazem, or verapamil are useful for ongoing management in patients without ventricular pre-excitation. 1, 2
• Verapamil up to 480 mg/day has documented reductions in SVT episode frequency and duration. 1
• Flecainide or propafenone may be used for patients without structural heart disease. 2

Transition from IV to Oral Therapy

When transitioning from esmolol to alternative drugs:

• Administer first dose of alternative agent, then reduce esmolol infusion by 50% after 30 minutes. 4
• After second dose of alternative agent, monitor for one hour; if control is satisfactory, discontinue esmolol. 4