What is the best treatment approach for a patient with Inappropriate Sinus Tachycardia (IST) and persistent symptoms of tachycardia, despite normal diagnostic test results, who is currently taking propranolol (Propranolol) and alprazolam (Alprazolam)?

Management of Inappropriate Sinus Tachycardia (IST)

Ivabradine is the most effective first-line therapy for symptomatic inappropriate sinus tachycardia, with superior efficacy compared to beta-blockers like propranolol. 1, 2

Diagnosis Confirmation

• Patient's symptoms (palpitations, heart "speeding up and stopping") match classic IST presentation
• 7-day event monitor confirms predominantly sinus rhythm (average HR 79 bpm, range 47-161 bpm)
• 32 patient-triggered events correlating with sinus rhythm/tachycardia
• Normal echocardiogram (LVEF 52%, normal valves)
• No evidence of other arrhythmias (no A-fib/flutter/SVT)

Treatment Algorithm

First-Line Therapy

1. Ivabradine

   • Start at 5 mg twice daily (as proposed in the case)
   • Can be titrated up to 7.5 mg twice daily based on heart rate response and symptom improvement 1, 2
   • Mechanism: Selectively inhibits If current in sinus node, providing pure negative chronotropic effect
   • Evidence: In a randomized crossover trial, ivabradine significantly reduced daytime heart rate from 98.4±11.2 to 84.7±9.0 bpm (p<0.001) and improved exercise tolerance 1
   • Multiple observational studies show complete symptom resolution in many patients 1

2. Beta-blockers

   • Only modestly effective for IST compared to ivabradine 1, 3
   • Can be used as needed for breakthrough symptoms (propranolol 10 mg twice daily PRN as proposed)
   • Discontinue standing daily dose of propranolol 80 mg when starting ivabradine

For Refractory Symptoms

• Combination therapy: Ivabradine plus beta-blocker may be considered for patients with particularly refractory symptoms 1
• In one observational study, combination therapy resolved symptoms in all patients 1
• Monitor closely for excessive bradycardia with combination therapy

Monitoring and Follow-up

• Follow-up in 2 weeks to assess medication effectiveness (as proposed)
• Monitor for side effects:
  • Phosphenes (enhanced brightness in visual field) - occurs in approximately 3% of patients, usually transient 1, 4
  • Excessive bradycardia, especially if combined with beta-blockers

Special Considerations

• Alprazolam may be helpful for anxiety component but is not a primary treatment for IST
• Avoid ablation procedures due to significant risks including:
  • Symptomatic bradycardia requiring pacemaker
  • Phrenic nerve injury
  • Superior vena cava syndrome
  • Only consider in highly symptomatic patients who fail medical therapy 1

Expected Outcomes

• Reduction in resting heart rate by approximately 20-30 bpm 2
• Improvement in exercise tolerance and symptoms 1, 2
• Some patients may maintain normal heart rate even after discontinuation of therapy 2, 4

The proposed treatment plan of switching from daily propranolol to ivabradine 5 mg twice daily with propranolol 10 mg PRN for breakthrough symptoms is well-supported by current guidelines and evidence.