Inappropriate sinus tachycardia: a review

Abstract

Inappropriate sinus tachycardia (IST) has been defined as a resting heart rate of >100 beats per minute and an average 24-hour heart rate >90 bpm with distressing symptoms resulting from the persistent tachycardia. IST is prevalent in 1% of the middle-aged population, mostly females. Rarely can elderly patients also present with IST. Possible mechanisms of IST include intrinsic sinus node abnormality, beta-adrenergic receptor stimulating autoantibody, beta-adrenergic receptor supersensitivity, muscarinic receptor autoantibody, or hyposensitivity, impaired baroreflex control, depressed efferent parasympathetic/vagal function, nociceptive stimulation, central autonomic overactivity, aberrant neurohumoral modulation, etc. Symptoms associated with IST are palpitations, chest pain, fatigue, shortness of breath, presyncope, and syncope. Despite these distressing symptoms, IST has not been associated with tachycardia-associated cardiomyopathy or increased major cardiovascular events. Various treatment options for patients with IST are ivabradine, beta-adrenergic blockers, calcium channel blockers, psychiatric evaluation, and exercise training. Although, endocardial radiofrequency ablation targeting the sinus node has been used as a treatment modality for otherwise treatment-refractory IST, the results have been dismal. The other modalities used for refractory IST treatment are endocardial modification of the sinus node using radiofrequency energy, combined endo and epicardial ablation of the sinus node, thoracoscopic epicardial ablation of the sinus node, sinus node sparing thoracoscopic and endocardial hybrid ablation. The goal of this review is to provide the readership with the pathophysiological basis of IST and its management options.

Refractory Inappropriate Sinus Tachycardia Treated with Pulsed-field Ablation of the Sinus Node: A Breath of Fresh Air

“…Endocardial RFA modification of the sinus node has limited success rates with significant complication rates. 3 , 4 The advantage of the PFA approach is that it will cause local tissue issue injury via electroporation but will not affect any collateral structures, which, in this case of sinus node modification, includes the phrenic nerve. Given the propensity for the creation of transmural scars with PFA, we anticipated the need for permanent pacemaker insertion to provide back-up atrial pacing; however, this was fortunately not required.…”

Translational Anatomy of the Sinoatrial Node

“… 3 SAN anatomical variations in shape, extent, and location within the sulcus terminalis and anatomical proximity to the phrenic nerve ( Figures 1A to 1C , Videos 1 and 2 ) have relevance for ablation therapy of atrial arrhythmias in this region. 4 , 5

Figure 1 Gross Anatomy and Histology of RA Structures and Anatomical Relationships (A) Lateral view of a human heart specimen showing the course of the right phrenic nerve (arrows) relative to the right atrium (RA). The location of the sinoatrial node (SAN) is outlined (blue dotted line).

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O eletrocardiograma aplicado a condições e demandas prevalentes na Atenção Primária à Saúde

“…A taquicardia sinusal 26 , a seu turno, é definida como a presença de batimentos sinusais em frequência que exceda 100 bpm. A causa da taquicardia sinusal é, em geral, aumento da automaticidade do nó sinusal, com aumento de sua excitabilidade.…”

“…Está com frequência relacionada a consumo de estimulantes, como álcool, alimentos com cafeína ou determinadas drogas (salbutamol, antidepressivos tricíclicos, adrenalina, atropina, entre outras). Não há grandes associações entre taquicardia sinusal e eventos cardiovasculares de maior gravidade 26 . Contudo, a condição, caso persistente e progressiva, deve ser cautelosamente investigada de modo a avaliar efeitos adversos de medicamentos usados, possíveis superdosagens e até mesmo eventuais reflexos hemodinâmicos.…”