Is Torpor (Verapamil) 25mg daily effective for managing Supraventricular Tachycardia (SVT) with a heart rate in the 60s?

Management of SVT with Heart Rate in the 60s on Verapamil 25mg Daily

Verapamil 25mg daily is likely excessive for this patient with SVT and a heart rate averaging in the 60s, and dose reduction should be considered to prevent excessive bradycardia while maintaining arrhythmia control.

Assessment of Current Therapy

Verapamil (Torpor) is a non-dihydropyridine calcium channel blocker that acts on nodal tissue to:

• Slow conduction through the AV node
• Terminate reentry PSVTs that depend on AV nodal conduction
• Control ventricular rate in atrial arrhythmias 1

Current Situation Analysis

• The patient has SVT but is currently experiencing a heart rate averaging in the 60s
• This suggests the 25mg daily dose of verapamil may be excessive
• Bradycardia is a known side effect of verapamil 1

Management Recommendations

Immediate Considerations

1. Evaluate for symptoms of bradycardia:

   • Fatigue
   • Dizziness
   • Syncope or near-syncope
   • Exercise intolerance

2. Assess for hemodynamic compromise:

   • Hypotension
   • Signs of decreased cardiac output

Treatment Algorithm

1. If patient is symptomatic with bradycardia:

   • Reduce verapamil dose to 20mg daily or consider alternate-day dosing
   • Monitor heart rate response
   • Consider switching to a different agent if symptoms persist

2. If patient is asymptomatic:

   • Options include:
     • Continue current dose with close monitoring if SVT is well-controlled
     • Reduce dose to 20mg daily if concerned about excessive bradycardia
     • Consider alternate-day dosing (25mg every other day)

3. If SVT is not adequately controlled:

   • Consider alternative therapy options:
     • Beta-blockers (if not contraindicated)
     • Catheter ablation for definitive treatment 1, 2

Evidence-Based Rationale

The American College of Cardiology/American Heart Association guidelines recommend oral calcium channel blockers like verapamil for ongoing management of symptomatic SVT 1. However, dosing must be carefully titrated to prevent excessive bradycardia.

Verapamil has been shown to be effective in terminating SVT in 64-98% of patients and is useful for long-term management 1. However, the guidelines emphasize monitoring for side effects including bradycardia and hypotension.

Important Considerations

• Avoid combination with other AV nodal blocking agents (beta-blockers, digoxin) as this can cause profound bradycardia 1
• Monitor for hypotension, especially if dose is increased
• Contraindications: Verapamil should not be used in patients with:
  • Impaired ventricular function
  • Heart failure
  • Pre-excited atrial fibrillation/flutter 1

Follow-up Recommendations

• ECG monitoring to assess heart rate and rhythm
• Clinical evaluation for symptoms of bradycardia
• Consider 24-hour Holter monitoring to assess heart rate throughout the day
• If symptoms persist or SVT is not adequately controlled, referral to a cardiac electrophysiologist for consideration of catheter ablation 2

Catheter ablation is a definitive treatment option with high success rates (>95%) for most SVT mechanisms and should be considered if medical therapy is ineffective or poorly tolerated 2.