title: Relationships between heart rate variability, functional capacity, and left ventricular function following myocardial infarction: an evaluation after one week and six months.
abstract: BACKGROUND
  Relationships between heart rate (HR) variability and different prognostic markers such as ejection fraction, functional capacity, and patency of the infarct-related artery, as well as the comparison of their time courses are not fully elucidated.
  
  
  OBJECTIVE
  The aim of study was to assess prospectively the early postinfarction changes in HR variability and its evolution over a period of 6 months: the relationships between HR variability and functional capacity in exercise testing; left ventricular function in cardiac catheterization: status of the infarct-related artery; and the comparison of their time courses.
  
  
  METHODS
  In 42 patients with anterior myocardial infarction, a study was made of the early changes in HR variability analyzed by the complex demodulation method, its evolution over a period of 6 months. and the relationships between HR variability and (1) functional capacity in exercise testing, (2) left ventricular function in cardiac catheterization, and (3) status of the infarct-related artery.
  
  
  RESULTS
  At 1 week HR variability parameters correlated directly with functional capacity indicators such as METS, percent change in HR from rest to peak exercise (%deltaHR), difference between initial and peak HR (HR range), percent peak theoretical HR (% peak HR), left ventricular ejection fraction (EF), and, inversely, with end-systolic volume (ESV). Stepwise multiple regression analysis to establish HR variability parameters (recorded at 1 week) as related to functional capacity and left ventricular function at 1 week and 6 months postinfarction established the following variables: (1) At 1 week: standard deviation (SD) of the RR cycles in relation to %deltaHR (r = 0.60, p <0.0001), HR range (r = 0.43, p < 0.01), and EF (r = 0.79, p < 0.0001). (2) At 6 months, the sole accepted HR variability parameter was the SD in relation to %deltaHR (r = 0.38, p < 0.05) and HR range (r = 0.45, p < 0.01). No variability parameter was accepted in relation to METS, % peak HR, or ESV. Relationship between EF or ESV and HR variability parameters was not significant when both were evaluated at 6 months. At that time, there was a significant increase in all HR variability parameters among all surviving patients (n = 39), with the exception of the LF/HF ratio and mean RR cycle. The percent increase in HR variability between the first week and 6 months was greater among those patients with the lowest basal EF. No relation was established between HR variability and patency of the infarct-related artery.
  
  
  CONCLUSIONS
  The decrease in HR variability observed following myocardial infarction is associated with a diminished functional capacity and an increased alteration of the EF. This does not affect the recovery of HR variability, which was observed in all surviving patients.
authors: Cardiology Service, University Clinic Hospital, Valencia, Spain.
authors: J V
authors: JV
authors: Monmeneu
authors: F J
authors: FJ
authors: Chorro
authors: V
authors: V
authors: Bodí
authors: J
authors: J
authors: Sanchis
authors: A
authors: A
authors: Llácer
authors: R
authors: R
authors: García-Civera
authors: R
authors: R
authors: Ruiz
authors: R
authors: R
authors: Sanjuán
authors: M
authors: M
authors: Burguera
authors: V
authors: V
authors: López-Merino
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D017023:Coronary Angiography; D003331:Coronary Vessels / Q000000981:diagnostic imaging; D004562:Electrocardiography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015635:Radionuclide Ventriculography; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology*