This study aimed to evaluate the effect of omega-3 supplementation on heart rate (HR) control and heart rate variability (HRV) in children with inappropriate sinus tachycardia (IST).

Inappropriate sinus tachycardia (IST) is a is a common disease of the autonomic nervous system in children in which tachyarrhythmia characterized by a persistent increase in resting sinus rate or disproportionate elevation of heart rate (HR) with minimal physiological effort accompanied by wide ranging symptoms including palpitations, fatigue, presyncope, and exercise intolerance it could cause lead to total disability in severe cases .it also takes a chronic course with Significant adverse effects on quality of life.

Inclusion Criteria:

• Age from 12 to 16 years.
• Both sexes.
• Patients diagnosed with inappropriate sinus tachycardia (IST).
• Patients with resting heart rate (HR) ≥100 bpm (sitting) and/or 24-hour average HR ≥90.

Exclusion Criteria:

• Structural heart disease.
• Patients receiving antiarrhythmic medication.
• Patients with a prior history of arrhythmias such as paroxysmal supraventricular tachycardia (PSVT) or sick sinus syndrome, or orthostatic hypotension.
• Secondary conditions such as anemia, infection, or hyperthyroidism.

The data will be available upon a reasonable request from the corresponding author after the end of study for one year.

After the end of study for one year.

The data will be available upon a reasonable request from the corresponding author.