Postural orthostatic tachycardia syndrome ( #POTS) is a complex, multifaceted disorder that commonly affect young #women & impairs functional status & quality of life

https://www.jacc.org/doi/10.1016/j.jacc.2020.12.029#.YCuW5WRmvQE.twitter

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POTS is characterised by #lightheadedness, #palpitations, #breathlessness, #headaches, #fatgue, #weakness & near #collapse upon assuming a standing position from a lying down, & is associated with an increase in heart rate by 30 bpm

This randomised controlled trial by @PamTaubMD published in @JACCJournals tested the effectiveness of #ivabrdine on quality of life for people with #POTS

Current pharmacological (drug) treatments are limited for #POTS

#POTS is currently understood to be composed of 5 subtypes: 1) hyperadrenergic; 2) neuropathic; 3) hypovolemic; 4) joint-hypermobility-related &
& 5) immune-related

The hyperadrenergic subtype, which comprises up to 50% of POTS, is characterized by abnormal sympathetic nervous system activation…

…& the body is in a constant “flight or fight” mode

For this study, hyperadrenergic POTS was defined by plasma NE >600 pg/ml & an abnormal head up tilt table test (HUTT)

HUTT was abnormal if patients had an increase in heart rate by at least 30bpm from baseline & experienced symptoms of orthostatic intolerance

The study was a randomized, double-blinded, placebo-controlled, crossover design

After randomization, patients were started on a 5mg twice daily dose of ivabradine or placebo

The medication dose was changed according to the
patient’s heart rate response and tolerance. If the resting supine heart rate was >70 bpm, doses were increased to 7.5 mg bd

Ivabradine has a unique & selective mechanism of action, which specifically blocks the Ifunny channel of the sinoatrial node, consequently lowering heart rate without lowering blood pressure

As part of the crossover design, patients on placebo were switched to ivabradine & patients on ivabradine were switched to placebo, following a 1 week wash out period

Medications in each arm were prescribed for 1 month

Quality of life was assessed using the RAND 36-Item Health Survey 1.0 (SF-36) questionnaire

The study found that ivabradine lowered heart rate compared with placebo & decreased the surge in heart rate upon standing

Patients reported improvements in quality of life with RAND 36-Item Health Survey 1.0 for physical functioning & social functioning

The reduction of NE levels upon standing with ivabradine was not found to be statistically significant

Notably, patients did not experience any significant side effects, such as bradycardia (slow heart rate) or hypotension (low blood pressure) with ivabradine

The authors conclude by stating that #ivabradine is safe & effective in improving heart rate and quality of life in patients with hyperadrenergic #POTS

Limitation of this study is the small sample size, therefore susceptible to false negative (type II) error. However, the study team actually found several statistically significant results

Another limitation is that although the study investigators & patients were blinded to the intervention, the study team report that many patients noticed differences & suspected that they were on ivabradine

To date, this is reported to be the first study of its kind to investigate the effects of ivabradine in patients with hyperadrenergic POTS as the predominant subtype in a randomized, double blinded, placebo-controlled, crossover trial

Read the full article by @PamTaubMD here @JACC https://www.jacc.org/doi/10.1016/j.jacc.2020.12.029#.YCuW5WRmvQE.twitter

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