title: Arterial baroreflex modulation of heart rate in patients early after heart transplantation: lack of parasympathetic reinnervation.
abstract: BACKGROUND
  Orthotopic heart transplantation results in cardiac denervation. The presence of cardiac parasympathetic reinnervation in humans has been widely debated based on the application of differing indirect measures of autonomic control. However no attempt has been made to analyse the reflex heart rate response to baroreceptor stimulation whose occurrence is generally considered a reliable marker of the ability to activate cardiac vagal reflexes. This study tested the hypothesis that the presence of donor heart RR interval lengthening following phenylephrine induced blood pressure increase would be an index of parasympathetic reinnervation.
  
  
  METHODS
  Baroreflex sensitivity (BRS) was assessed in 30 patients (mean age 51+/-12 years) 1-24 months after heart transplantation carried out by the standard Lower-Shumway technique. In 6 patients the recipient atrium rate response (P-P interval) to baroreceptor stimulation by phenylephrine was also simultaneously determined by transesophageal recording.
  
  
  RESULTS
  None of the 30 patients showed prolongation of RR intervals in the donor heart. The average BRS value was -0.28+/-0.54 ms/mmHg (range -1.3-0.7 ms/mm Hg). In the 6 patients in whom BRS was obtained at both the recipient atrium (P-P) and donor heart (R-R) the changes were 7.6+/-5.7 ms/mm Hg and -0.38+/-0.58 ms/mm Hg respectively (p = 0.02), thus confirming that the absent RR interval lengthening in the donor heart is the consequence of efferent vagal fiber interruption.
  
  
  CONCLUSIONS
  The absence of any RR interval prolongation following phenylephrine induced baroreceptor stimulation demonstrates that vagal efferent reinnervation of the donor heart does not occur up to 24 months in patients operated via the standard Lower-Shumway procedure. It is also suggested that analysis of baroreceptor reflexes is a more specific method in the examination of cardiac parasympathetic reinnervation.
authors.affiliation: II Department of Cardiology, Medical University of Gdańsk, Poland.
authors.forename: G
authors.initials: G
authors.lastname: Raczak
authors.forename: M T
authors.initials: MT
authors.lastname: La Rovere
authors.forename: A
authors.initials: A
authors.lastname: Mortara
authors.forename: J
authors.initials: J
authors.lastname: Assandri
authors.forename: A
authors.initials: A
authors.lastname: Prpa
authors.forename: G D
authors.initials: GD
authors.lastname: Pinna
authors.forename: R
authors.initials: R
authors.lastname: Maestri
authors.forename: A M
authors.initials: AM
authors.lastname: D'Armini
authors.forename: M
authors.initials: M
authors.lastname: Viganó
authors.forename: F
authors.initials: F
authors.lastname: Cobelli
mesh_terms: D001158:Arteries / Q000187:drug effects / Q000502:physiology; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006321:Heart / Q000294:innervation; D006339:Heart Rate / Q000502:physiology*; D016027:Heart Transplantation / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009416:Nerve Regeneration; D010656:Phenylephrine; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology* / Q000601:surgery; D014662:Vasoconstrictor Agents
chemical_list: D014662:Vasoconstrictor Agents; D010656:Phenylephrine