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

The pathogenesis of inappropriate sinus tachycardia is not well understood, and the symptoms of inappropriate sinus tachycardia can be difficult to manage. Here, we present a case of inappropriate sinus tachycardia refractory to medical therapy and discuss our approach to sinus node modification by catheter ablation.

Inappropriate Sinus Tachycardia: Etiology, Pathophysiology, and Management: JACC Review Topic of the Week

Inappropriate sinus tachycardia (IST) is a clinical syndrome that generally affects young patients and is associated with distressing symptoms. Although the most common symptom is palpitations, it can be accompanied by a myriad of symptoms, including anxiety, dizziness, presyncope, and syncope. The pathogenesis of IST is not well understood and considered multifactorial, with autonomic dysfunction being the central abnormality. IST is a diagnosis of exclusion. Management presents a clinical challenge. The overall efficacy of lifestyle modifications and medical therapy may be limited. Recent advances in catheter and surgical sinus node sparing ablation techniques have led to improvement in outcomes. In addition, increased focus has led to development of multimodality team-based interventions to improve outcomes in this group of patients. In this review, we discuss the mechanistic basis of IST, review current approaches to diagnosis, and outline contemporary therapeutic approaches.

Combined Epicardial and Endocardial Sinus Node Modification Using the Orion™ Mini-basket Mapping Catheter

In patients with inappropriate sinus tachycardia, conservative medical management targeting the relief of symptoms is the first line of therapy. Sinus node modification can offer a potential benefit in selected patients with severe, refractory inappropriate sinus tachycardia. Extensive endocardial radiofrequency (RF) ablation of the superior aspect of the sinus node complex is typically required but is often limited by the epicardial location of the sinus node and the proximity of the phrenic nerve. More recently, surgical and catheter-based epicardial approaches to the sinus node have been used to facilitate more direct access to the sinus node and mechanical displacement of the phrenic nerve from ablation target sites. In this case report, we describe a combined epicardial-endocardial sinus node modification procedure in a patient with refractory inappropriate sinus tachycardia and previous unsuccessful endocardial ablation. The Orion™ mini-basket catheter (Boston Scientific, Natick, MA, USA) was used both for mapping the sinus node and for mechanically displacing the phrenic nerve from ablation target sites, which facilitated successful ablation.

Efficacy of medical and ablation therapy for inappropriate sinus tachycardia: A single-center experience

BACKGROUND

Effective therapy for inappropriate sinus tachycardia (IST) remains challenging with high rates of treatment failure and symptom recurrence. It is uncertain how effective pharmacotherapy and procedural therapy are long-term, with poor response to medical therapy in general.

METHODS

We retrospectively reviewed all patients with the diagnosis of IST at a tertiary academic medical center from 1998 to 2018. We extracted data related to prescribing patterns and symptom response to medical therapy and sinus node modification (SNM), assessing efficacy and periprocedural complication rates.

RESULTS

A total of 305 patients with a formal diagnosis of IST were identified, with 259 (84.9%) receiving at least one prescription medication related to the condition. Beta-blockers were the most commonly used medication (n = 245), with a majority of patients reporting no change or worsening of symptoms, and poor response was seen to other medication classes. Improvement was seen significantly more often with ivabradine than beta blockers, though the sample size was limited (p = .003). Fifty-five patients (18.0% of all IST patients), mean age 32.0 ± 9.1 years, underwent a SNM procedure, with an average of 1.8 ± 0.9 procedures per patient. Acute symptomatic improvement (<6 months) was seen in 58.2% of patients. Long-term complete resolution of symptoms was seen in 5.5% of patients, modest improvement in 29.1%, and no long-term benefit was seen in 65.5% of patients.

CONCLUSIONS

Among all medical therapies, there were high rates of treatment failure or symptom worsening in over three-quarters of patients in our study. Ivabradine was most beneficial, though the sample size was small. While most patients receiving SNM ablation for IST perceive an acute symptomatic improvement, almost two-thirds of patients have no long-term improvement, and resolution of symptoms is quite rare. AV node ablation with pacemaker implantation following lack of response to SNM offered increased success, though the sample size was limited.