What is the initial management approach for a patient with Supraventricular Tachycardia (SVT)?

Initial Management of Supraventricular Tachycardia

For hemodynamically stable SVT patients, begin with vagal maneuvers immediately, followed by intravenous adenosine if unsuccessful, while hemodynamically unstable patients require immediate synchronized cardioversion. 1, 2

Immediate Assessment: Hemodynamic Stability

Determine hemodynamic stability first - this dictates your entire management pathway. Unstable patients present with altered mental status, hypotension, acute heart failure, or ongoing chest pain indicating ischemia. 1

For Hemodynamically Unstable Patients

• Perform synchronized cardioversion immediately if vagal maneuvers and adenosine fail or are not feasible - this is a Class I recommendation with proven safety and effectiveness. 1
• Do not delay cardioversion attempting multiple pharmacologic agents in unstable patients. 1

For Hemodynamically Stable Patients

Step 1: Vagal Maneuvers (First-Line)

• Attempt vagal maneuvers first - these are Class I recommended initial interventions with a 27.7% overall success rate when switching between techniques. 1, 2

Specific techniques to employ:

• Modified Valsalva maneuver (most effective): Patient bears down against a closed glottis for 10-30 seconds in the supine position, generating at least 30-40 mm Hg intrathoracic pressure - this achieves 43% effectiveness. 1, 2, 3
• Carotid sinus massage: Apply steady pressure over the right or left carotid sinus for 5-10 seconds, but only after confirming absence of carotid bruits by auscultation. 1, 2
• Diving reflex: Apply an ice-cold, wet towel to the face or facial immersion in 10°C water. 1, 2

Critical pitfall to avoid: Never apply pressure to the eyeball - this practice is dangerous and has been abandoned. 1, 2

Step 2: Adenosine (First-Line Pharmacotherapy)

• Administer intravenous adenosine if vagal maneuvers fail - this is a Class I recommendation with 91-95% effectiveness for terminating AVNRT. 1, 2, 3
• Adenosine serves dual purposes: therapeutic termination and diagnostic unmasking of atrial activity in flutter or atrial tachycardia. 1

Step 3: Alternative Pharmacologic Agents

If adenosine fails or is contraindicated, proceed with AV nodal blocking agents:

• Intravenous diltiazem or verapamil are particularly effective for converting AVNRT to sinus rhythm with 80-98% success rates - these are Class IIa recommendations. 1, 2
• Intravenous beta-blockers are reasonable alternatives with excellent safety profiles, though less effective than calcium channel blockers (Class IIa recommendation). 1, 2

Critical safety considerations before administering calcium channel blockers or beta-blockers:

• Confirm absence of ventricular tachycardia - these agents can cause hemodynamic collapse and ventricular fibrillation if given for VT or pre-excited atrial fibrillation. 1, 2
• Avoid in suspected systolic heart failure - calcium channel blockers and beta-blockers should not be used in patients with heart failure. 1
• Avoid in pre-excitation syndromes (Wolff-Parkinson-White) - AV nodal blocking agents may accelerate ventricular rate and precipitate ventricular fibrillation. 1, 2

Step 4: Refractory Cases

• Oral combination therapy with diltiazem plus propranolol may be reasonable when IV access is unavailable (Class IIb recommendation). 1
• Intravenous amiodarone may be considered when other therapies are ineffective or contraindicated (Class IIb recommendation). 1
• Synchronized cardioversion is recommended for stable patients when pharmacologic therapy fails or is contraindicated (Class I recommendation). 1

Special Population: Pre-Excited Atrial Fibrillation

This requires different management:

• Hemodynamically unstable: Immediate synchronized cardioversion (Class I). 2
• Hemodynamically stable: Intravenous ibutilide or procainamide (Class I recommendation). 2
• Never use AV nodal blockers (verapamil, diltiazem, beta-blockers, adenosine) - these can be lethal in pre-excited AF. 2

Post-Conversion Management

• Obtain 12-lead ECG in sinus rhythm to assess for pre-excitation (delta waves) and guide long-term management. 2, 4
• Refer all patients to cardiology for consideration of electrophysiology study and catheter ablation, which has 94.3-98.5% single-procedure success rates and is first-line therapy for preventing recurrence. 2, 3, 5
• Patient education on vagal maneuvers for self-termination of future episodes. 2