title: Beat-to-beat estimate of fetal cardiac time intervals using magnetocardiography: longitudinal charts of normality ranges and individual trends.
abstract: BACKGROUND
  Fetal magnetocardiography (fMCG) records fetal cardiac electro-physiological activity during the second half of gestation. We aimed at assessing normality values, related variability, and trends of fetal cardiac time intervals (fCTI) evaluated longitudinally from beat-to-beat fMCG analysis in uncomplicated pregnancies.
  
  
  METHODS
  The fMCG were recorded with multi-channel system in shielded room. FCTI were estimated on more than 2600 fetal cardiac cycles from 51 fMCG data sets of uncomplicated pregnancies. Independent component analysis (ICA) allowed reconstructing reliable fetal signals for beat-to-beat identification of fCTI (RR, P wave, PQ, PR, QT, QTc, QRS, ST, and T wave); intra-individual variability analysis and trends were calculated; reference longitudinal charts accounted for intra- and inter-individual variations and were compared with figures estimated on averaged signals.
  
  
  RESULTS
  For each data set, fCTI were calculated beat-to-beat on rhythm strips of more than 50 beats (95% overall detection rate). FCTI values, variability, and trends were in good agreement with available reference figures; intervals related to P and T waves were, respectively, underestimated and overestimated with respect to those estimated on averaged signals or obtained by other research groups. Errors were reduced and individual trends could be drawn.
  
  
  CONCLUSIONS
  ICA permitted the reconstruction of reliable time course of fetal cardiac signals and the beat-to-beat calculation of time intervals, and normality ranges, with smaller errors with respect to previous studies. The retrieval of fetal traces with clear morphology and the longitudinal character of the study allowed estimating individual trends and beat-to-beat characterization, impossible with cross-sectional studies on averaged beats.
authors.affiliation: ITAB-Institute of Advanced Biomedical Technologies, University Foundation G. D'Annunzio, Via dei Vestini 33, 66013 Chieti, Italy. comani@itab.unich.it
authors.forename: Silvia
authors.initials: S
authors.lastname: Comani
authors.forename: Marco
authors.initials: M
authors.lastname: Liberati
authors.forename: Dante
authors.initials: D
authors.lastname: Mantini
authors.forename: Biagio
authors.initials: B
authors.lastname: Merlino
authors.forename: Giovanna
authors.initials: G
authors.lastname: Alleva
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Gabriele
authors.forename: Silvano
authors.initials: S
authors.lastname: Di Luzio
authors.forename: Gian Luca
authors.initials: GL
authors.lastname: Romani
mesh_terms: D000328:Adult; D015148:Cardiotocography; D005260:Female; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third