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The effects of phrenic nerve stimulation on heart rate variability: a case study

Session Poster Session 4

Speaker Andrew Coats

Event : Heart Failure 2019

  • Topic : heart failure
  • Sub-topic : Chronic Heart Failure: Comorbidities
  • Session type : Poster Session

Authors : AJ Coats (Warwick,AU), REG Germany (Oklahoma City,US), DW Bourn (Minnetonka,US), LR Goldberg (Philadelphia,US)

AJ Coats1 , REG Germany2 , DW Bourn3 , LR Goldberg4 , 1Monash University - Warwick - Australia , 2University of Oklahoma - Oklahoma City - United States of America , 3Cardialen, Inc. - Minnetonka - United States of America , 4University of Pennsylvania, Medicine - Philadelphia - United States of America ,


Introduction: Frequency based heart rate variability (HRV) measures are one method of measuring autonomic function and sympatho-vagal balance via subtle changes in R-R interval timing. The proportions of these measures describe the autonomic function and sympatho –vagal balance of a patient and are reflected in Total Power (TP), and Very Low Frequency (VLF), Low Frequency (LF) and High Frequency (HF) power. Heart failure patients with reduced Ejection Fraction (HFrEF) exhibit high levels of sympathetic drive, depressed baroreceptor responsiveness (LF), and decreased vagal tone (HF via respiration). Central sleep apnoea (CSA), a co-morbid condition often seen in HFrEF patients, contributes to increased sympathetic drive and is manifested by increases in the VLF component. Treatment of CSA using the remede® System has been shown to be effective in restoring a normal breathing pattern and may also contribute to improved autonomic function and sympatho–vagal balance.

Purpose:  To describe changes in HRV measures after 6 months of phrenic nerve stimulation experienced by a patient with reduced ejection fraction (EF) and CSA.

Methods: The remede® System pivotal trial assessed the effectiveness of unilateral phrenic nerve stimulation in treating moderate to severe CSA. In this analysis, overnight attended polysomnography studies performed at baseline (BL) and at 6 months of treatment (6M) were divided into 5-minute segments and the EKG was analysed by segment using an automated algorithm in Lab Chart (v8.1) HRV module. All segments were reviewed to ensure accuracy and consistency in the analysis. Here we present a single case of a trial participant that had an EF = 40%, was in normal sinus rhythm, and demonstrated an improvement in CSA as evidenced by a reduction in the Apnoea-Hypopnoea Index from 49 to 9 events/hour at 6M.

Results: The figure below shows the median values of the 5 minute segments for the VLF, LF and HF components of the HRV Measures. At BL (n=90, 5 min. segments) the total power is dominated by the VLF content while at 6M (n=84, 5 min. segments) the total power decreases by 20% and VLF decreases by 69% (Figure 1). Additionally, LF and HF power increased by 207 and 247% respectively, demonstrating decreased sympathetic drive.

Discussion:  In this case study, CSA improved at 6 months with phrenic nerve stimulation and the improvement corresponded to changes in magnitude and content of frequency domain HRV measures that suggest improved autonomic function and sympatho-vagal balance.  Further analysis is required in a larger sample of patients to validate this unique finding.

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