title: Effects of acute mental stress and exercise on T-wave alternans in patients with implantable cardioverter defibrillators and controls.
abstract: BACKGROUND
  Malignant cardiac arrhythmias can be triggered by exercise and by mental stress in vulnerable patients. Exercise-induced T-wave alternans (TWA) is an established marker of cardiac electrical instability. However, the effects of acute mental stress on TWA have not been investigated as a vulnerability marker in humans.
  
  
  RESULTS
  TWA responses to mental stress (anger recall and mental arithmetic) and bicycle ergometry were evaluated in patients with implantable cardioverter defibrillators (ICDs) and documented coronary artery disease (n=23, age 62.1+/-12.3 years) and controls (n=17, age 54.2+/-12.1 years). TWA was assessed from digitized ECGs by modified moving average analysis. Dual-isotope single photon emission computed tomography was used to assess myocardial ischemia. TWA increased during mental stress and exercise (P values <0.001), and TWA responses were higher in ICD patients than in controls (arithmetic Delta=8.9+/-1.4 versus 4.3+/-2.2 microV, P=0.043; exercise Delta=21.4+/-2.8 versus 13.8+/-3.2 microV, P=0.038). TWA increases with mental stress occurred at substantially lower heart rates (anger recall Delta=9.7+/-7.7 bpm, arithmetic Delta=14.3+/-13.3 bpm) versus exercise (Delta=53.7+/-22.7 bpm; P values <0.001). After adjustment for heart rate increases, mental stress and exercise provoked increased TWA in ICD patients (P values <0.05), but not in controls (P values >0.2). Ejection fraction and stress-induced myocardial ischemia were not associated with TWA.
  
  
  CONCLUSIONS
  Mental stress can induce cardiac electrical instability, as assessed via TWA, among patients with arrhythmic vulnerability and occurs at lower heart rates than with exercise. Pathophysiological mechanisms of mental stress-induced arrhythmias may therefore involve central and autonomic nervous system pathways that differ from exercise-induced arrhythmias.
authors.affiliation: Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd, Bethesda, Md 20814, USA. wjkop@usuhs.mil
authors.forename: Willem J
authors.initials: WJ
authors.lastname: Kop
authors.forename: David S
authors.initials: DS
authors.lastname: Krantz
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Nearing
authors.forename: John S
authors.initials: JS
authors.lastname: Gottdiener
authors.forename: John F
authors.initials: JF
authors.lastname: Quigley
authors.forename: Mark
authors.initials: M
authors.lastname: O'Callahan
authors.forename: Albert A
authors.initials: AA
authors.lastname: DelNegro
authors.forename: Ted D
authors.initials: TD
authors.lastname: Friehling
authors.forename: Pamela
authors.initials: P
authors.lastname: Karasik
authors.forename: Sonia
authors.initials: S
authors.lastname: Suchday
authors.forename: Joseph
authors.initials: J
authors.lastname: Levine
authors.forename: Richard L
authors.initials: RL
authors.lastname: Verrier
mesh_terms: D000208:Acute Disease; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000209:etiology; D001794:Blood Pressure; D035061:Control Groups; D003324:Coronary Artery Disease / Q000150:complications / Q000628:therapy; D017147:Defibrillators, Implantable; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000209:etiology; D013315:Stress, Psychological / Q000150:complications*; D016277:Ventricular Function, Left