title: Cardiac autonomic function in adolescents operated by arterial switch surgery.
abstract: BACKGROUND
  Children with transposition of the great arteries, in whom an arterial switch operation (ASO) is performed, have been shown to have an increased incidence of sudden death, which may be due to cardiac autonomic imbalance and repolarisation instability. We hypothesised that i) cardiac norepinephrine (NE) kinetics and ii) arterial baroreflex sensitivity (BRS), reflecting sympathetic activity and vagal function respectively, are altered in this group.
  
  
  RESULTS
  17 children (15.8 ± 1.5 years of age) with ASO-surgery in the neonatal period were studied. 17 had cardiac BRS assessed by spontaneous fluctuations of systolic blood pressure and RR-interval, and repolarisation was measured as QT variability index. Matched healthy subjects were controls. Cardiac vagal function and repolarisation pattern were unchanged following ASO-surgery. At cardiac catheterisation, we infused tritiated NE in 8 of these children to examine total body and cardiac sympathetic function at baseline and following 5 min of adenosine infusion to induce reflex sympathetic activation. Blood was sampled simultaneously from the aorta and coronary sinus. Cardiac fractional extraction of ([3H])NE was substantially lower in operated children, being 56 ± 10 vs. 82 ± 9% (p=0.0001). Following i.v. adenosine in the operated group, NE total body spillover doubled vs. baseline (p<0.002) and the coronary venous-arterial concentration gradient of ([3H])dihydroxyphenylglycol increased 4-fold (p=0.04).
  
  
  CONCLUSIONS
  Arterial switch operation performed neonatally appears to leave cardiac vagal function intact and, although cardiac sympathetic activation in response to adenosine occurs, cardiac neuronal NE reuptake is impaired. This may be pro-arrhythmic by reducing removal capacity of NE from the cardiac synaptic cleft.
authors: Division of Paediatric Cardiology, Institute of Clinical Sciences, Sahlgrenska University Hospital, Gothenburg University, Sweden.
authors: Cecilia
authors: C
authors: Falkenberg
authors: Ingegerd
authors: I
authors: Östman-Smith
authors: Thomas
authors: T
authors: Gilljam
authors: Gavin
authors: G
authors: Lambert
authors: Peter
authors: P
authors: Friberg
mesh_terms: D000293:Adolescent; D001341:Autonomic Nervous System / Q000503:physiopathology*; D017704:Baroreflex / Q000502:physiology*; D006348:Cardiac Surgical Procedures; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006321:Heart / Q000294:innervation* / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D011184:Postoperative Period; D012189:Retrospective Studies; D014188:Transposition of Great Vessels / Q000503:physiopathology* / Q000601:surgery
keywords: Adolescents; Autonomic nervous system; Congenital heart disease; Heart; Transposition of the great arteries