title: Global impairment of cardiac autonomic nervous activity late after the Fontan operation.
abstract: BACKGROUND
  Atrial tachyarrhythmia is a common cause of morbidity and mortality in patients with univentricular physiology undergoing the Fontan operation. We examined cardiac autonomic nervous activity, a predictor of arrhythmia and sudden death in other cardiovascular disease, in patients late after the Fontan operation, employing heart rate variability (HRV) and baroreflex sensitivity.
  
  
  RESULTS
  We measured HRV and baroreflex sensitivity in 22 consecutive patients (8 male, age 26+/-9 years) who had undergone the Fontan operation 13+/-6 years previously, and 22 age- and sex-matched healthy controls. Fontan patients had significantly lower HRV (P<0.0001). Baroreflex sensitivity was measured by the alpha-index method (square root of ratio of RR interval spectral power to systolic blood pressure (SBP) spectral power, in the LF and the HF band) and was also significantly depressed in the Fontan group (P<0.0001 for both). Both low frequency (LF) and high frequency (HF) components of HRV were reduced in the Fontan patients (P<0.0001), but there was interindividual variation so that the LF/(LF+HF) ratio may be high, normal, or low, and decreased with increasing right atrial dimensions (r=-0.62, P=0.006). Patients with a history of sustained atrial arrhythmia had a stronger baroreflex than those without (P=0.005).
  
  
  CONCLUSIONS
  Autonomic nervous control of the heart is markedly deranged in patients late after the Fontan operation, with reduced HRV and baroreflex sensitivity. A relative suppression of the sympathetic-compared with the parasympathetic-system was observed in patients with marked right atrial dilation within the Fontan group. Furthermore, stronger baroreflexes were seen in Fontan patients in association with a higher incidence of sustained atrial tachyarrhythmia, implying that sinus node dysfunction is unlikely to be the dominant mechanism. Additional studies are clearly required to examine the prognostic importance of impaired BRS and HRV in these patients.
authors.affiliation: Royal Brompton Adult Congenital Heart Programme, and Department of Clinical Cardiology, Royal Brompton Hospital and National Heart and Lung Institute, Imperial College School of Medicine, London, UK.
authors.forename: Constantinos H
authors.initials: CH
authors.lastname: Davos
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.forename: Marjolein F E
authors.initials: MF
authors.lastname: Leenarts
authors.forename: Sing-Chien
authors.initials: SC
authors.lastname: Yap
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Periklis A
authors.initials: PA
authors.lastname: Davlouros
authors.forename: Roland
authors.initials: R
authors.lastname: Wensel
authors.forename: Andrew J S
authors.initials: AJ
authors.lastname: Coats
authors.forename: Massimo
authors.initials: M
authors.lastname: Piepoli
authors.forename: Narayanswami
authors.initials: N
authors.lastname: Sreeram
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gatzoulis
mesh_terms: D000293:Adolescent; D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D017704:Baroreflex; D002648:Child; D005260:Female; D018729:Fontan Procedure; D006321:Heart / Q000294:innervation*; D006330:Heart Defects, Congenital / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery*; D006339:Heart Rate; D006801:Humans; D008297:Male; D011446:Prospective Studies; D013564:Sympathetic Nervous System / Q000503:physiopathology; D013610:Tachycardia / Q000209:etiology; D014630:Vagus Nerve / Q000503:physiopathology