Inappropriate sinus tachycardia

Abstract

Inappropriate sinus tachycardia (IST) is a clinical syndrome, oftentimes debilitating, defined by fast sinus rates (>100 b.p.m. at rest or >90 b.p.m. on average over 24 h and not due to underlying causes) associated with symptoms that may include palpitations, as described in some guidelines and consensus documents. While heart rates may vary by patient, especially based upon gender and age, some individuals experience sinus tachycardia or persistent fast sinus rates with no symptoms; these individuals would not necessarily be considered to have the syndrome of IST. Various explanations for IST have been considered but a definitive common mechanism is not yet known; the true aetiology may be multifactorial. A thorough evaluation of secondary causes of tachycardia is required in the work-up of all cases and if found, must be treated before a diagnosis of IST can be made. Finally, effective treatments vary but can include ivabradine, beta-blockers, or calcium channel antagonists; ablation is seldom advised.

Natural history and clinical outcomes of inappropriate sinus tachycardia

“…IST has been hypothesized to be linked to viral infections, though no cases have been reported in the literature . A syndrome with overlapping features to IST, POTS, has a prevalence of 27.6% of patients reporting a preceding illness before the development of the condition .…”

“…IST has been thought to be a condition typically found in young females, though there are reports of patients diagnosed in their 6th and 7th decade of life . Symptoms of IST are quite broad and include palpitations, chest pain, weakness, lightheadedness, fatigue, and exercise intolerance . Isolated case reports within the literature have described IST causing tachycardia‐induced cardiomyopathy, challenging the notion that IST is an isolated benign condition.…”

What Have We Learned from the European Society of Cardiology 2019 Guidelines on Supraventricular Tachycardia

“…Treatment of reversible causes is recommended in recent guidelines. (1) Inappropriate sinus tachycardia (IST) is defined as a sinus rhythm >100 bpm at rest or minimal activity with disproportionately faster than expected [24]. The diagnosis of IST is based on the exclusion of the other arrhythmias such as physiologic sinus tachycardia, postural orthostatic tachycardia syndrome, sinus re-entrant tachycardia, or focal AT from the superior part of the crista terminalis or right superior pulmonary veins.…”

Patient Selection for Epicardial Ablation—Part I: The Role of Epicardial Ablation in Various Cardiac Disease States

“…76 Additional studies need to be performed to determine the safety and efficacy of endocardial-epicardial ablation in patients with refractory IST. 77 In many cases of IST, the risks of ablation may outweigh the benefits, and the procedure is not currently recommended in the guidelines as first-line therapy.…”