Atrioventricular Node Ablation and Pacemaker Implantation for Recurrent Syncope in a Patient With Postural Tachycardia Syndrome (POTS)

Randomized Trial of Ivabradine in Patients With Hyperadrenergic Postural Orthostatic Tachycardia Syndrome

BACKGROUND

Postural orthostatic tachycardia syndrome (POTS) is a complex, multifaceted disorder that impairs functional status and quality of life. Current pharmacological treatments are limited.

OBJECTIVES

This study investigated the effect of ivabradine (selective blocker of the I_funny channel in the sinoatrial node) on heart rate, quality of life (QOL), and plasma norepinephrine (NE) levels in patients with hyperadrenergic POTS defined by plasma NE >600 pg/ml and abnormal tilt table test.

METHODS

In total, 22 patients with hyperadrenergic POTS as the predominant subtype completed a randomized, double-blinded, placebo-controlled, crossover trial with ivabradine. Patients were randomized to start either ivabradine or placebo for 1 month, and then were crossed over to the other treatment for 1 month. Heart rate, QOL, and plasma NE levels were measured at baseline and at the end of each treatment month.

RESULTS

The average age was 33.9 ± 11.7 years, 95.5% were women (n = 21), and 86.4% were White (n = 23). There was a significant reduction in heart rate between placebo and ivabradine (p < 0.001). Patients reported significant improvements in QOL with RAND 36-Item Health Survey 1.0 for physical functioning (p = 0.008) and social functioning (p = 0.021). There was a strong trend in reduction of NE levels upon standing with ivabradine (p = 0.056). Patients did not experience any significant side-effects, such as bradycardia or hypotension, with ivabradine.

CONCLUSION

Ivabradine is safe and effective in significantly improving heart rate and QOL in patients with hyperadrenergic POTS as the predominant subtype.

Work Ability Assessment and Its Relationship with Cardiovascular Autonomic Profile in Postural Orthostatic Tachycardia Syndrome

Postural orthostatic tachycardia syndrome (POTS) negatively impacts quality of life. The excessive increase in cardiac sympathetic modulation during standing, which characterizes POTS patients, leads to many symptoms and signs of orthostatic intolerance. Little is known about the consequences of the disease on work performance and its relationship with individual autonomic profiles. Twenty-two POTS patients regularly engaged in working activity (20 females, age 36 ± 12 years) and 18 gender- and age-matched controls underwent a clinical evaluation and filled out the Work Ability Index (WAI) questionnaire. POTS patients completed the Composite Autonomic Symptom Score (COMPASS31) questionnaire, underwent continuous electrocardiogram, blood pressure and respiratory activity recordings while supine and during a 75° head-up tilt (HUT). A power spectrum analysis provided the index of cardiac sympatho-vagal balance (LF/HF). WAI scores were significantly reduced in POTS patients (29.84 ± 1.40) compared to controls (45.63 ± 0.53, p < 0.01). A significant inverse correlation was found between individual WAI and COMPASS31 scores (r = −0.46; p = 0.03), HUT increase in heart rate (r = −0.57; p = 0.01) and LF/HF (r = −0.55; p = 0.01). In POTS patients, the WAI scores were inversely correlated to the intensity of autonomic symptoms and to the excessive cardiac sympathetic activation induced by the gravitational stimulus.

Ivabradine in Postural Orthostatic Tachycardia Syndrome: A Review of the Literature

Postural orthostatic tachycardia syndrome (POTS) is an autonomic disorder characterized by symptoms such as palpitations, dyspnea, chest discomfort, and lightheadedness affecting various systems. The pathophysiology of POTS is not completely understood due to a variety of symptoms showing that the disease is multifactorial. There is no approved uniform management strategy for POTS and hence, no drug has been approved by the United States (US) Food and Drug Administration (FDA) for it. Ivabradine is an FDA-approved drug for stable symptomatic heart failure (HF) and patients with an ejection fraction (EF) of ≤35%. Previous studies have depicted improvement in symptoms of POTS with the use of ivabradine. It is a selective inhibitor of funny sodium channels (I_f) in the sinoatrial (SA) node cells resulting in the prolongation of the slow diastolic depolarization (phase IV) and reduction in the heart rate (HR). Although beta-adrenoceptor blockers are commonly used to lower HR in patients with POTS, they are less ideal due to numerous adverse effects. This review aims to provide a comprehensive and up-to-date picture of all the studies and case reports that utilized ivabradine for the treatment of POTS along with a precise overview of epidemiology, pathophysiology, and types of POTS. To conclude, we recommend further research on the effectiveness of ivabradine in patients who experience symptoms of POTS. Other than stable chronic angina pectoris, its application in this setting has been proven to be effective and safe. Further evaluation by means of randomized control trials is required to encourage use of this HR-lowering agent in common disorders other than HF and stable angina, i.e. POTS.

Is ivabradine a wonder drug for atypical POTS?

Syncope is a sudden loss and gain of consciousness. Traditionally, it is caused by the abnormalities of neurological, cardiac or vasovagal systems. We present a case of a 19-year-old woman presenting with recurrent syncopal episodes with no apparent cause. Examination and investigations were unremarkable for any aetiology except positive tilt tests for postural orthostatic tachycardia syndrome. The purpose of this report is to make physicians aware of the unique presentation of this rare aetiology with recurrent syncopal episodes and the novel management approach.

Ivabradine for the Treatment of Postural Orthostatic Tachycardia Syndrome: A Systematic Review

INTRODUCTION

Postural orthostatic tachycardia syndrome (POTS) impacts millions of patients, but there is currently no gold standard treatment for this condition. Ivabradine is a novel heart rate (HR) lowering agent that acts on the sinoatrial node cells by selectively inhibiting the If-current.

OBJECTIVE

The objective of this systematic review is to evaluate the evidence for the efficacy and safety of ivabradine for the treatment of POTS.

METHODS

MEDLINE (from 1956 to August 2017) and EMBASE (from 1957 to August 2017) were queried with the following search term: "postural orthostatic tachycardia syndrome" OR "postural tachycardia syndrome" OR "chronic orthostatic intolerance" AND "ivabradine." Articles in English with clinical outcomes of human patient(s) treated with ivabradine for POTS were included.

RESULTS

The initial search identified 73 articles. After screening, 13 articles were included. Two prospective open-label trials, three retrospective cohort studies, and eight case reports evaluated the safety and efficacy of ivabradine in a total of 132 patients with postural tachycardia. Overall, ivabradine lowered HR and provided symptomatic relief of POTS without blood pressure lowering. Dizziness, nausea, headache, and fatigue were the most common side effects and often did not lead to discontinuation of treatment.

CONCLUSION

Based on this small sample, ivabradine appears to be a reasonable option for patients with POTS who have failed or are unable to tolerate other treatment options, however, but a randomized controlled trial in this population is needed.