Obstructive Sleep Apnea Destabilizes Myocardial Repolarization Homogeneity
Condition: Obstructive Sleep Apnea; Heart Rhythm Disorder; Obesity, Abdominal
MeSH terms: Apnea; Sleep Apnea Syndromes; Sleep Apnea, Obstructive; Arrhythmias, Cardiac; Obesity, Abdominal
Study type: Observational [Patient Registry]

Summary: 
      Literature shows that patients with obesity and Obstructive Sleep Apnea (OSA), both occurring
      independently, are more likely to develop cardiovascular diseases and sudden cardiac death
      (SCD). Assuming that ventricular depolarization is more stable than repolarization then QT
      interval parameters may be used for heart muscle repolarization assessment for those groups
      of patients.

      There were 121 patients included in the study, both - women and men, aging from 35-65 with
      visceral obesity. Only healthy patients were included - the ones who were not treated for any
      chronic disease, taking QT elongating drugs, or were not treated with Continuous Positive
      Airway Pressure (CPAP) therapy at that time.
    

Detailed description: 
      The current study was a prospective, observational clinical trial performed between September
      2016 and August 2019 at a single-center institution specializing in treatment of patients
      with obstructive sleep apnea. The inclusion criteria were as follows: (1) gender: female or
      male, (2) age 35-65 years old, (3) visceral obesity, (4) lack of acute or chronic diseases
      that may have an influence on rhythm or conduction disorders, (5) not undergoing Continuous
      Positive Airway Pressure therapy (CPAP) or taking drugs that have or may have an influence on
      QT interval duration [according to Credible Meds list (Woosley et al, 2019)], (6) not
      consuming grapefruits or grapefruit juice for at least 2 weeks before Holter-ECG examination.
      Patients, who met all inclusion criteria, underwent subject and physical examination, an
      over-night Holter-ECG, polygraphy and laboratory biochemical tests (sodium, potassium,
      calcium, magnesium concentration and fasting glyceamia.

      Enrolled patients were asked questions about general frame of mind, daytime and nighttime
      symptoms that may suggest OSA [according to Epworth Sleepiness Scale
      (https://epworthsleepinessscale.com/about-the-ess/ access date 08 May 2020)]. All patients
      were fully physically examined. Neck and waist circumference were measured according to
      STEPwise Approach to Surveillance (STEPS) by WHO
      (https://www.who.int/ncds/surveillance/steps/en/. [access date 23 April.2019]. Upon subject
      examination (snoring and choking feeling during the sleep) a corrected neck circumference was
      calculated.

      Polygraphy was conducted using MED Recorder device by Infoscan company according to AASM
      guidelines (American Academy of Sleep Medicine, International classification of sleep
      disorders, 2016). The device registered blood saturation, heart rate, airflow, chest and
      abdomen movements, body position, snoring and single lead ECG. OSA was diagnosed according to
      AASM definition (American Academy of Sleep Medicine, Sleep-related breathing disorders in
      adults, 1999): in every patient with Respiratory Disturbance Index (RDI) ≥ 5/hour and with
      concomitant OSA sings (Epworth Sleepiness Scale ≥ 11 pts) or with RDI ≥ 15/hour. The minimum
      time of analyzed data without artifacts had to last at least 6 h.

      A Holter-ECG examination was conducted using DMS 300-3A device by Oxford company suitable for
      Cardioscan 10 system. Registration was made simultaneously with polygraphy, during the night.
      Chosen QT interval assessment parameters were evaluated upon partially automatically analyzed
      fragments of ECG records. Only nighttime ECG records were analyzed due to maximum
      comparability (similar patient's physical activity and minimized, because of limited body
      movements, artifacts). Moreover, the study aimed to assess a heart's activity simultaneous to
      sleep breathing disorders. Only ECG strips with constant heart rate, optimally within
      50-70/min limits, were chosen due to the minimum impact of such heart rate on QT interval
      correction formula. QTc data was calculated upon Bazett's formula. QTV and QTVi were
      calculated upon Berger's formula.

      After getting all results they were checked against the following exclusion criteria: 1)
      revealing that information about patient's chronic illness or drugs therapy was obfuscated,
      revealing increased fasting serum glucose concentration or ionic disturbances. It was
      strongly recommended to every patient to visit their GP for further diagnostics, 2) revealing
      any important deviation in physical examination i.a. blood pressure taken twice at the visit
      ≥140/ ≥90 mmHg, 3) revealing, upon Holter ECG examination, tachycardia or too numerous
      artifacts making QT interval assessment incredible, 4) too short total sleep time (< 6 hours)
      registered on polygraphy.

      Out of 187 consecutive patients meeting the inclusion criteria, 66 patients met at least one
      exclusion criterion, leaving 121 patients for the study analyses.
    

Intervention name(s): Polygraphy monitoring; laboratory tests
Intervention type(s): Diagnostic Test; Diagnostic Test
Intervention description(s): All patients with visceral obesity have been tested for Obstructive Sleep Apnea and heart rhythm disorders by usage of polygraphy and Holter-ECG monitoring.; Blood samples for sodium, potassium, calcium, magnesium concentration and fasting glyceamia assessment hae been taken from all patients with visceral obesity.
Other intervention name(s): Holter ECG monitoring
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Out of 187 consecutive patients meeting the inclusion criteria, 66 patients met at least
        one exclusion criterion, leaving 121 patients for the study analyses.
      
Keywords: Obstructive Sleep Apnea; QT interval; QTV; QTc; repolarisation homogeneity