title: Increased T wave complexity can indicate subclinical myocardial ischemia in asymptomatic adults.
abstract: BACKGROUND
  Altered ventricular repolarization and cardiovascular mortality are closely correlated, and recent novel findings show that a distorted T wave loop morphology is also strongly correlated with subsequent onset of myocardial infarction among patients with stable angina. Therefore, we hypothesized that an abnormal T wave complexity ratio (CR) can indicate vulnerability to myocardial ischemia in asymptomatic, apparently healthy adults.
  
  
  METHODS
  Healthy firefighters were enrolled in the current investigation where they completed symptom-limited, graded exercise treadmill testing (ETT) and 24-hour Holter electrocardiogram recording. The CR was automatically calculated using principal component analysis of the high-resolution Holter electrocardiogram signal then averaged over 24 hours (CR(24h)). End points were manually analyzed from the ETT; recordings revealing horizontal ST-segment depression (≥ 1 mm) in 2 or more leads for at least 1 minute during the peak of exercise were considered indicators of myocardial ischemia.
  
  
  RESULTS
  One hundred four firefighters (age, 44 ± 8 years; 96% men) completed both ETT and Holter recording. Firefighters with positive end points (n = 34, or 33%) had higher CR(24h) compared with those with negative end points (0.14 ± 0.06 vs 0.09 ± 0.04, P < .01); there were no demographic differences between the 2 groups. After controlling for age, smoking status, hypertension, and obesity, an abnormal CR(24h) (≥ 20%) significantly predicted exercise-induced myocardial ischemia (odds ratio, 4.6; P = .01).
  
  
  CONCLUSIONS
  Increased T wave CR(24h) can predict myocardial ischemia in asymptomatic middle-age adults; this suggests that the distorted T wave loop morphology can reflect an altered ventricular repolarization caused by prolonged subclinical myocardial ischemia possibly caused by early coronary artery disease.
authors.affiliation: School of Nursing, The State University of New York, University at Buffalo, Buffalo, NY 14214, USA. ssabdel@buffalo.edu
authors.forename: Salah S
authors.initials: SS
authors.lastname: Al-Zaiti
authors.forename: Kristen N
authors.initials: KN
authors.lastname: Runco
authors.forename: Mary G
authors.initials: MG
authors.lastname: Carey
mesh_terms: D000328:Adult; D015716:Electrocardiography, Ambulatory; D005080:Exercise Test; D005260:Female; D061388:Firefighters; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D017202:Myocardial Ischemia / Q000175:diagnosis*