title: QRS-T morphology measured from exercise electrocardiogram as a predictor of cardiac mortality.
abstract: OBJECTIVE
  Total cosine R-to-T (TCRT) measured from the standard 12-lead electrocardiogram (ECG) reflects the spatial relationship between depolarization and repolarization wavefronts and a low TCRT value is a marker of poor prognosis. We tested the hypothesis that measurement of TCRT or QRS/T angle from exercise ECG would provide even more powerful prognostic information.
  
  
  RESULTS
  The prognostic significances of TCRT and QRS/T angle were assessed from exercise ECG recordings in 1297 patients [age 56 ± 13 years (mean ± SD), 67% males] undergoing a clinically indicated bicycle stress-test and the subsequent follow-up. During an average follow-up of 45 ± 12 months, 74 patients died (5.7%); 34 (2.6%) were cardiac deaths, and 24 (1.9%) were sudden cardiac deaths. Total cosine R-to-T and QRS/T angle exhibited a correlation with the RR intervals in the total cohort, but the individual responses were variable, e.g. median correlation of TCRT-RR was 0.89 with an inter-quartile range from 0.55 to 0.98. A reduced correlation of TCRT-RR during the recovery phase of exercise ECG predicted cardiac death [adjusted heart rate (HR) 3.5, 95% confidence interval (CI): 1.8-6.8, P= 0.001] similarly as the baseline TCRT measured from ECG at rest (adjusted HR 3.4, 95% CI: 1.4-8.1, P= 0.01). The poor correlation between the TCRT-RR both during the exercise and recovery was specifically related to a risk of sudden cardiac death (adjusted HR 6.2, 95% CI: 2.1-17.8, P< 0.001).
  
  
  CONCLUSIONS
  Loss of rate-adaptation of the spatial relationship between depolarization and repolarization wavefronts is a strong predictor of cardiac death, especially of sudden cardiac death.
authors.affiliation: Division of Cardiology, Institute of Clinical Medicine, University of Oulu, Oulu, Finland. tuomas.kentta@oulu.fi
authors.forename: Tuomas
authors.initials: T
authors.lastname: Kenttä
authors.forename: Mari
authors.initials: M
authors.lastname: Karsikas
authors.forename: M Juhani
authors.initials: MJ
authors.lastname: Junttila
authors.forename: Juha S
authors.initials: JS
authors.lastname: Perkiömäki
authors.forename: Tapio
authors.initials: T
authors.lastname: Seppänen
authors.forename: Antti
authors.initials: A
authors.lastname: Kiviniemi
authors.forename: Tuomo
authors.initials: T
authors.lastname: Nieminen
authors.forename: Terho
authors.initials: T
authors.lastname: Lehtimäki
authors.forename: Kjell
authors.initials: K
authors.lastname: Nikus
authors.forename: Rami
authors.initials: R
authors.lastname: Lehtinen
authors.forename: Jari
authors.initials: J
authors.lastname: Viik
authors.forename: Mika
authors.initials: M
authors.lastname: Kähönen
authors.forename: Heikki V
authors.initials: HV
authors.lastname: Huikuri
mesh_terms: D000328:Adult; D000368:Aged; D016757:Death, Sudden, Cardiac / Q000453:epidemiology*; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006331:Heart Diseases / Q000175:diagnosis* / Q000401:mortality*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D012307:Risk Factors; D013318:Stroke Volume