August 2026 Br J Cardiol 2026;33(3) doi:10.5837/bjc.2026.040 Online First
Matthew Laird, Paul Foley
Introduction Inappropriate sinus tachycardia (IST) is a rare, potentially debilitating syndrome, characterised by persistent or paroxysmal sinus tachycardia in the presence of symptoms, such as palpitations, chest discomfort, dyspnoea, fatigue, or syncope.1 It is a diagnosis of exclusion, defined by an elevated resting heart rate (HR) in the absence of an identifiable physiological cause.1,2 Prevalence is estimated at around 1%, with a predominance in young women.2 The pathogenesis remains poorly understood, but appears multi-factorial, with autonomic dysfunction a central abnormality.1 In many individuals, IST is a self-limiting condition, a
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