BERLIN, Germany,

Study Shows Severe Fainting Can Be Treated with Cardiac Pacing Supported by Closed Loop Stimulation

A new study1 presented at this year’s European Society of Cardiology (ESC) Congress today shows that BIOTRONIK’s exclusive Closed Loop Stimulation (CLS) helps reduce unexplained fainting in patients with recurrent episodes due to skipped heartbeats.

The BIOSync study1 found that dual-chamber pacemaker supported by the CLS algorithm is highly effective in reducing the recurrence of asystolic vasovagal syncope – caused by temporary pause in the heart beat.

The multi-center study – the largest of its kind - was a double-blind, randomized and placebo controlled trial conducted across 24 sites in Italy, France, Spain, Portugal, Netherlands and Canada between 2015 and 2020, with a medium follow-up of 11.2 months. It had a sample size of 127 patients.

A vasovagal reflex is a frequent cause of unexplained loss of consciousness. In extreme cases this results in an asystolic pause which leads to severe syncope events. In addition to the impact caused by these syncopes on patients’ health, patients can become increasingly distressed due to the high frequency and unpredictable nature of these events – further hindering their quality of life.

When comparing the CLS-paced group versus the control group, the BIOSync study found that after two years:

  • Syncope recurrence rate was reduced by 77 per cent, and
  • The combined rate of syncope and/or pre-syncope was reduced by 56 per cent.

Additionally, until this study, the use of tilt-table testing to select patients with severe recurrent reflex syncope for cardiac pacing was controversial. The positive results demonstrated through this trial indicate that asystolic response to these tests is a valuable criterion for cardiac pacing.

“Dual-chamber pacemaker with CLS has the potential to provide significant relief for patients suffering from severe unexplained syncope,” said Prof. Michele Brignole, Istituto Auxologico Italiano, Ospedale San Luca in Italy, principal investigator of the BIOSync study. “Patients who have tried alternative therapies with no success, can now efficiently be treated through pacing, giving them more options to treat their distressing condition.”

“This trial provided promising results in the ability to use tilt-testing as a method for selecting pacemaker candidates and will help avoid delays in diagnosis and treatment for patients,” said Dr. Marco Tomaino, Central Hospital of Bolzano, Italy, co-chairman of the BIOSync study.

BIOTRONIK’s CLS is an algorithm which identifies changes in a patient’s cardiac contractility and translates this data to deliver proper heart rate adaptation – promoting more effective physiological therapy. This technology is exclusive to BIOTRONIK.



  1. The Benefit of Dual-Chamber Pacing with Closed Loop Stimulation in Tilt-Induced Cardioinhibitory Reflex Syncope (BIOSync CLS) study, reference number: NCT02324920.



At BIOTRONIK, patient well-being is our top priority and has been for 60 years. BIOTRONIK is a leading global medical technology company with products and services that save and improve the lives of millions suffering from heart and blood vessel diseases. Driven by a purpose to perfectly match technology with the human body, we are dedicated innovators who develop trusted cardiovascular and endovascular solutions. BIOTRONIK is headquartered in Berlin, Germany, and is represented in over 100 countries.