What is the treatment approach for a patient presenting with supraventricular tachycardia (SVT), considering their medical history and potential underlying health conditions?

Treatment of Supraventricular Tachycardia

Begin with vagal maneuvers immediately, followed by adenosine if unsuccessful, and proceed to synchronized cardioversion for hemodynamically unstable patients or those who fail pharmacological therapy. 1

Acute Management Algorithm

Step 1: Initial Assessment and Vagal Maneuvers

Vagal maneuvers are the first-line intervention for all hemodynamically stable SVT patients and should be performed before any pharmacological therapy. 1

• Modified Valsalva maneuver is the most effective vagal technique: patient bears down against a closed glottis for 10-30 seconds (generating 30-40 mmHg pressure), then immediately lies flat with legs raised 2, 3
• The modified Valsalva has a 5.47-fold higher success rate compared to carotid sinus massage 3
• Carotid sinus massage (after confirming absence of bruit): apply steady pressure over right or left carotid sinus for 5-10 seconds 1
• Ice-cold towel to face (diving reflex): apply ice-cold wet towel to face or facial immersion in 10°C water 1
• Overall success rate when switching between techniques reaches 27.7% 1
• Critical caveat: Avoid eyeball pressure (dangerous and abandoned) 1

Step 2: Pharmacological Therapy (if vagal maneuvers fail)

Adenosine is the first-line medication with 90-95% effectiveness for terminating SVT. 1, 2

• Dosing: 6 mg rapid IV bolus followed immediately by saline flush 2
• If unsuccessful, give 12 mg rapid IV bolus 1
• Adenosine terminates AVNRT in approximately 95% of patients and serves as both therapeutic and diagnostic agent 1
• Important safety consideration: Adenosine is safe during pregnancy due to short half-life 2

Alternative agents for hemodynamically stable patients who don't respond to adenosine: 1

• IV calcium channel blockers (diltiazem or verapamil): particularly effective with 80-98% success rates 1
• IV beta blockers (metoprolol or esmolol): reasonable alternative though less effective than calcium channel blockers 1
• Critical warning: Never give verapamil or diltiazem if VT or pre-excited atrial fibrillation is suspected—this can cause hemodynamic collapse or ventricular fibrillation 1
• Avoid calcium channel blockers in patients with suspected systolic heart failure 1

Step 3: Electrical Cardioversion

Synchronized cardioversion is mandatory for hemodynamically unstable patients when adenosine and vagal maneuvers fail or are not feasible. 1

• Synchronized cardioversion is highly effective, terminating SVT in the vast majority of cases 1
• Also indicated for hemodynamically stable patients when pharmacological therapy fails or is contraindicated 1
• Safe at all stages of pregnancy if necessary 2

Special Population Considerations

Pregnancy

• Vagal maneuvers remain first-line and are safe 2
• Adenosine is safe due to short half-life 2
• Avoid atenolol and verapamil due to teratogenic effects 4
• Synchronized cardioversion can be performed safely at all trimesters 2, 4

Pre-excitation (Wolff-Parkinson-White)

• Avoid all AV nodal blocking agents (adenosine, calcium channel blockers, beta blockers) 2
• Use ibutilide or IV procainamide for hemodynamically stable pre-excited atrial fibrillation 2
• Synchronized cardioversion for hemodynamically unstable patients 5

Elderly Patients (>65 years)

• Consider proceeding directly to verapamil rather than vagal maneuvers due to higher risk of coronary and cerebrovascular disease with carotid massage 6

Long-term Management

Beta blockers are the first-line option for long-term prevention of recurrent SVT. 2

• Calcium channel blockers serve as alternative to beta blockers 2
• Catheter ablation is curative and indicated for: 2
  • Frequent symptomatic episodes
  • Poor tolerance or ineffectiveness of medications
  • Patient preference for non-pharmacological approach

Critical Diagnostic Considerations

Always obtain a 12-lead ECG before treatment to differentiate tachycardia mechanisms. 1, 2

• Essential to distinguish SVT with aberrancy from ventricular tachycardia before initiating treatment 2
• If QRS >120 ms, must rule out VT before giving calcium channel blockers 1
• Determine if AV node is obligate component of circuit, as this guides therapy 1

Common Pitfalls to Avoid

• Never use verapamil/diltiazem for wide-complex tachycardia of uncertain etiology—this can be fatal if rhythm is VT 1
• Never use AV nodal blockers in pre-excitation syndromes with atrial fibrillation—can accelerate ventricular rate and cause ventricular fibrillation 2, 5
• Don't perform carotid massage without first auscultating for bruits 1
• Ensure vagal maneuvers are performed with patient in supine position for maximum effectiveness 1, 2