title: Heart Rate Variability as an Alternative Indicator for Identifying Cardiac Iron Status in Non-Transfusion Dependent Thalassemia Patients.
abstract: BACKGROUND
  Iron-overload cardiomyopathy is a major cause of death in thalassemia patients due to the lack of an early detection strategy. Although cardiac magnetic resonance (CMR) T2* is used for early detection of cardiac iron accumulation, its availability is limited. Heart rate variability (HRV) has been used to evaluate cardiac autonomic function and found to be depressed in thalassemia. However, its direct correlation with cardiac iron accumulation has never been investigated. We investigated whether HRV can be used as an alternative indicator for early identification of cardiac iron deposition in thalassemia patients.
  
  
  METHODS
  Ninety-nine non-transfusion dependent thalassemia patients (23.00 (17.00, 32.75) years, 35 male) were enrolled. The correlation between HRV recorded using 24-hour Holter monitoring and non-transferrin bound iron (NTBI), hemoglobin (Hb), serum ferritin, LV ejection fraction (LVEF), and CMR-T2* were determined.
  
  
  RESULTS
  The median NTBI value was 3.15 (1.11, 6.59) μM. Both time and frequency domains of HRV showed a significant correlation with the NTBI level, supporting HRV as a marker of iron overload. Moreover, the LF/HF ratio showed a significant correlation with CMR-T2* with the receiver operating characteristic (ROC) curve of 0.684±0.063, suggesting that it could represent the cardiac iron deposit in thalassemia patients. HRV was also significantly correlated with serum ferritin and Hb.
  
  
  CONCLUSIONS
  This novel finding regarding the correlation between HRV and CMR-T2* indicates that HRV could be a potential marker in identifying early cardiac iron deposition prior to the development of LV dysfunction, and may be used as an alternative to CMR-T2* for screening cardiac iron status in thalassemia patients.
authors.affiliation: Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Center of Excellence in Cardiac Electrophysiology, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Karn
authors.initials: K
authors.lastname: Wijarnpreecha
authors.affiliation: Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Center of Excellence in Cardiac Electrophysiology, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Natthaphat
authors.initials: N
authors.lastname: Siri-Angkul
authors.affiliation: Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Center of Excellence in Cardiac Electrophysiology, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Krekwit
authors.initials: K
authors.lastname: Shinlapawittayatorn
authors.affiliation: Center of Excellence in Cardiac Electrophysiology, Chiang Mai University, Chiang Mai, Thailand; Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Pimlak
authors.initials: P
authors.lastname: Charoenkwan
authors.affiliation: Center of Excellence in Cardiac Electrophysiology, Chiang Mai University, Chiang Mai, Thailand; Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Suchaya
authors.initials: S
authors.lastname: Silvilairat
authors.affiliation: Department of Radiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Chate
authors.initials: C
authors.lastname: Siwasomboon
authors.affiliation: Department of Radiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Pannee
authors.initials: P
authors.lastname: Visarutratna
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Somdet
authors.initials: S
authors.lastname: Srichairatanakool
authors.affiliation: Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Adisak
authors.initials: A
authors.lastname: Tantiworawit
authors.affiliation: Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Arintaya
authors.initials: A
authors.lastname: Phrommintikul
authors.affiliation: Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Center of Excellence in Cardiac Electrophysiology, Chiang Mai University, Chiang Mai, Thailand; Department of Oral Biology and Diagnostic Sciences, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Siriporn C
authors.initials: SC
authors.lastname: Chattipakorn
authors.affiliation: Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Center of Excellence in Cardiac Electrophysiology, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Nipon
authors.initials: N
authors.lastname: Chattipakorn
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D004452:Echocardiography; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000209:etiology; D006339:Heart Rate; D006801:Humans; D007501:Iron / Q000378:metabolism*; D019190:Iron Overload / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D012372:ROC Curve; D013318:Stroke Volume; D013789:Thalassemia / Q000150:complications*; D055815:Young Adult
chemical_list: D007501:Iron