title: Atrioventricular conduction and cardiovascular mortality: assessment of recovery PR interval is superior to pre-exercise measurement.
abstract: BACKGROUND
  A prolonged electrocardiographic PR interval at rest has been considered a benign phenomenon until recently.
  
  
  OBJECTIVE
  We hypothesized that measurement of the PR interval during recovery from physical exertion could improve cardiovascular mortality risk stratification because it would track the dynamic influences of homeostatic mechanisms controlling atrioventricular (AV) conduction.
  
  
  METHODS
  A total of 1,979 consecutive patients (1,244 men and 735 women) with clinically indicated bicycle ergometer tests enrolled in FINCAVAS (the Finnish Cardiovascular Study) were included in the study. The PR interval was measured at 1 min before and at 2 min after exercise.
  
  
  RESULTS
  During the mean follow-up period of 47 months (interquartile range: 37 to 59 months), 50 cardiovascular deaths (end point) were registered. The unadjusted hazard ratios (HR) in Cox regression analyses were significant for both continuous PR interval and first-degree atrioventricular (AV) block for pre- and post-exercise phases. After adjustment for standard markers, the PR interval for 20-ms increments (HR: 1.17, P = .117) and first-degree AV block (HR: 1.85, P = .138) during the pre-exercise phase were not prognostic. However, during recovery from exercise, prolonged AV conduction achieved significance both in continuous (HR: 1.29, P = .006) and dichotomized analyses (HR: 2.41, P = .045).
  
  
  CONCLUSIONS
  The PR interval before exercise is not a robust risk stratifier for cardiovascular death during 4-year follow-up. Post-exercise assessment of AV conduction may offer improved prediction because of functional abnormalities that become manifest only during this physiologic challenge to the heart.
authors.affiliation: Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA. tuomo.nieminen@iki.fi
authors.forename: Tuomo
authors.initials: T
authors.lastname: Nieminen
authors.forename: Richard L
authors.initials: RL
authors.lastname: Verrier
authors.forename: Johanna
authors.initials: J
authors.lastname: Leino
authors.forename: Kjell
authors.initials: K
authors.lastname: Nikus
authors.forename: Rami
authors.initials: R
authors.lastname: Lehtinen
authors.forename: Terho
authors.initials: T
authors.lastname: Lehtimäki
authors.forename: Mikko
authors.initials: M
authors.lastname: Minkkinen
authors.forename: Tiit
authors.initials: T
authors.lastname: Kööbi
authors.forename: Väinö
authors.initials: V
authors.lastname: Turjanmaa
authors.forename: Jari
authors.initials: J
authors.lastname: Viik
authors.forename: Mika
authors.initials: M
authors.lastname: Kähönen
mesh_terms: D000222:Adaptation, Physiological; D001283:Atrioventricular Node / Q000473:pathology*; D002318:Cardiovascular Diseases / Q000401:mortality* / Q000473:pathology; D004562:Electrocardiography / Q000295:instrumentation / Q000379:methods; D016552:Ergometry; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006305:Health Status Indicators; D006329:Heart Conduction System / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012044:Regression Analysis; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors