title: Recovery of autonomic nervous activity after myocardial infarction demonstrated by short-term measurements of SDNN.
abstract: OBJECTIVE
  Heart rate variability (HRV) has been demonstrated to be a risk factor after acute myocardial infarction (AMI). In the present study serial measurement of SDNN (standard deviation of the mean of qualified NN-interval) in short intervals was used to assess HRV changes after AMI, and determine the role of these as independent risk factors compared to clinical, arrhythmic, ischemic and anamnestic variables. Measurements from a normal healthy middle-aged male population were used as reference (n = 63).
  
  
  METHODS
  SDNN from a five-minute period during day and night-time, respectively, was examined in 103 patients 1 week (n = 54), 1 month (n = 72) and 12-16 months (n = 54) after infarction.
  
  
  RESULTS
  Day SDNN did not change during one-and-a-half years after AMI, and was significantly reduced compared with healthy males. Night SDNN, low after 1 week, with recovery 1 month after AMI, was significantly reduced compared with healthy males early, but not late after AMI. Thus, the study indicated during day-time a continuous abnormal sympathetic preponderance in the course of 16 months after AMI, and during night-time a gradual recovery of parasympathetic preponderance beginning early after AMI.
  
  
  CONCLUSIONS
  One week after AMI day-time SDNN of <30 ms, and night-time SDNN of < 18 ms, age > or =60 years, and myocardial ischemia (Holter monitoring) were independent predictors of 9 years' mortality. One and 12-16 months after AMI reduced day and night-time SDNN had no prognostic implication.
authors.affiliation: Department of Cardiology, Hvidovre University Hospital, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Vaage-Nilsen
authors.forename: V
authors.initials: V
authors.lastname: Rasmussen
authors.forename: G
authors.initials: G
authors.lastname: Jensen
authors.forename: L
authors.initials: L
authors.lastname: Simonsen
authors.forename: L S
authors.initials: LS
authors.lastname: Mortensen
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology; D001341:Autonomic Nervous System / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology*; D017202:Myocardial Ischemia / Q000503:physiopathology; D011379:Prognosis; D013997:Time Factors; D018879:Ventricular Premature Complexes / Q000503:physiopathology*