title: Detecting acute graft rejection in patients after orthotopic heart transplantation: analysis of heart rate variability in the frequency domain.
abstract: BACKGROUND
  Acute transplant rejection is a major complication after heart transplantation. To treat patients with rejection, early detection is necessary before fatal heart dysfunction. Because of its invasive aspect, endomyocardial biopsy is limited with respect to its frequency and complication rate. Little work has been done so far to develop noninvasive methods for detecting rejection, and, hence, investigation for such methods would seem to be of considerable value.
  
  
  METHODS
  After routine endomyocardial biopsy in 117 heart transplant recipients (age 49 +/- 13 years time after transplantation 6 to 48 months), electrocardiography results were recorded with the patient in a supine position at a controlled respiratory rate (0.25 Hz) over 10 minutes. Patients with an artificial pacemaker or severe arrhythmia were excluded. On the basis of endomyocardial biopsy reports, two groups of patients were defined: patients without rejection (AR0, n = 73) and patients with severe rejection (AR1b to AR4, n = 32). The spectra of R-wave to R-wave intervals were calculated, and different spectral components were evaluated: low frequency (LF, 0.05 to 0.18 Hz), high frequency (HF, 0.18 to 0.5 Hz), LF + HF, LF + HF minus the respiratory peak (RP) (LF + HF - RP), and the total power (0 to 0.5 Hz).
  
  
  RESULTS
  All frequency domain parameters except HF were significantly higher in patients with severe rejection than in patients without rejection. By means of the calculation of receiver operating characteristic curves, LF + HF - RP was the most reliable frequency domain parameter for the detection of severe rejection. Setting its threshold value to 5 msec2, 77% sensitivity, and 76% specificity could be achieved.
  
  
  CONCLUSIONS
  Spectral analysis of heart rate variability may be used as a noninvasive tool to detect severe rejection episodes.
authors.affiliation: Herz-Zentrum Bad Krozingen, Herzchirurgie Grosshadern, Germany.
authors.forename: A W
authors.initials: AW
authors.lastname: Frey
authors.forename: P
authors.initials: P
authors.lastname: Uberfuhr
authors.forename: H
authors.initials: H
authors.lastname: Achakri
authors.forename: A
authors.initials: A
authors.lastname: Fuchs
authors.forename: B
authors.initials: B
authors.lastname: Reichart
authors.forename: K
authors.initials: K
authors.lastname: Theisen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001146:Arrhythmia, Sinus / Q000175:diagnosis / Q000209:etiology; D002648:Child; D004562:Electrocardiography; D005260:Female; D006084:Graft Rejection / Q000175:diagnosis*; D006339:Heart Rate; D016027:Heart Transplantation; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012119:Respiration; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted