What is Inappropriate Sinus Tachycardia

Inappropriate Sinus Tachycardia (IST) is a condition where the heart beats faster than normal at rest or with minimal activity, without an underlying cause such as fever, dehydration, or other medical conditions. The fast heart rate arises from abnormal regulation of the sinus node, the heart’s natural pacemaker.

Common Symptoms:

  • Persistent or rapid resting heart rate (often >100 bpm)

  • Palpitations or awareness of the heartbeat

  • Fatigue and exercise intolerance

  • Dizziness or light-headedness

  • Shortness of breath

  • Anxiety or feelings of “racing heart”

Diagnosis:

  • Electrocardiogram (ECG) to monitor heart rhythm

  • Holter monitor or event monitor to track heart rate over time

  • Exclusion of other causes of rapid heart rate (thyroid issues, anemia, medications etc.)

Management Strategies:

  • Lifestyle modifications: pacing activity, managing stress, and avoiding stimulants (caffeine, certain medications)

  • Exercise programs: gentle, structured cardiovascular activity to improve tolerance

  • Medications: beta-blockers or other heart-rate controlling drugs may be prescribed under specialist supervision

  • Monitoring & Support: ongoing assessment by a cardiologist or autonomic specialist is often recommended

Inappropriate Sinus Tachycardia (IST)