Inappropriate sinus tachycardia — ailment or disease?

Abstract

We present a case of a 36-year-old female patient with a long history of persistent palpitations, limited exercise tolerance, and pre-syncope. ECG recordings revealed long lasting episodes of inappropriate sinus tachycardia (IST). IST is characterised by persistent cardiac arrhythmias with sinus P waves in the ECG, and an exaggerated response to a minimal physical effort or stress. Using 24-h Holter definition the average heart rate in patients with IST should be > 90 bpm or daytime heart rate > 100 bpm. The syndrome is associated neither with structural heart disease nor with any reversible causes of sinus tachycardia (i.e. fever, anemia, infection, hyperthyroidism, drug abuse). Therefore the diagnosis is generally one of exclusion. Beta-blockers are most frequently used as first line therapy. Other potentially effective drugs are nondihydropyridine calcium antagonists or ivabradine. The prognosis in patients with IST is very good but in some cases the symptoms can be severe and debilitating.