title: Cardiac repolarization instability during psychological stress in patients with ventricular arrhythmias.
abstract: BACKGROUND
  Changes in the autonomic nervous system activity are a major trigger of life-threatening ventricular tachyarrhythmias (VTAs). Mental arithmetic, a condition administered in a laboratory setting, can provide insight into the autonomic nervous system activity effects on cardiac physiology. We examined the responses of cardiac repolarization to laboratory-induced psychological stressors in patients with implantable cardioverter-defibrillators (ICDs) with the objective of identifying the indices that differentiate patients with and without subsequent VTA in follow-up.
  
  
  METHODS
  Continuous electrocardiographic signals were recorded using 3 standard bipolar (Holter) leads in 56 patients (age, 63.6 ± 11.9; female, 12%; left ventricular ejection fraction, 32.3 ± 11) with ICDs during mental arithmetic. The patients were separated into those with subsequent VTA during 3 to 4 years of follow-up (group 1: n = 9) and those without VTA (group 2: n = 47). Changes in repolarization (QT interval, mean T wave amplitude [Tamp], and T wave area) were analyzed during 5 minutes at baseline, stress, and recovery. The temporal instability of Tamp and T wave area was examined using the range (Δ) and variance (σ(2)) of beat-to-beat variations of the corresponding parameters.
  
  
  RESULTS
  There were no significant differences in heart rate between the 2 groups at baseline (61 vs 63 beats per minute, P = .97), stress (64 vs 65 beats per minute, P = .40), and recovery (62 vs 61 beats per minute, P = .88). However, during mental stress and poststress recovery, ΔTamp was almost 2-fold greater in group 1 compared with group 2 (111 [57-203] vs 68 [44-94] μV, P = .04, respectively). Changes in QT intervals were also greater in group 1 compared with group 2 (P = .02).
  
  
  CONCLUSIONS
  Among patients with ICDs, changes of Tamp after psychological stress were greater in those with subsequent arrhythmic events. This might signal proarrhythmic repolarization response and help identify patients who would benefit the most from ICD implantation and proactive management.
authors.affiliation: Cardiovascular Institute, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
authors.forename: Saddam S
authors.initials: SS
authors.lastname: Abisse
authors.forename: Rachel
authors.initials: R
authors.lastname: Lampert
authors.forename: Matthew
authors.initials: M
authors.lastname: Burg
authors.forename: Robert
authors.initials: R
authors.lastname: Soufer
authors.forename: Vladimir
authors.initials: V
authors.lastname: Shusterman
mesh_terms: D000368:Aged; D002395:Catecholamines / Q000097:blood; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D013315:Stress, Psychological / Q000097:blood / Q000503:physiopathology*; D017180:Tachycardia, Ventricular / Q000503:physiopathology* / Q000523:psychology
chemical_list: D002395:Catecholamines