title: Cardiac Iodine-123-Meta-Iodo-Benzylguanidine Uptake in Carotid Sinus Hypersensitivity.
abstract: BACKGROUND
  Carotid sinus syndrome is the association of carotid sinus hypersensitivity with syncope, unexplained falls and drop attacks in generally older people. We evaluated cardiac sympathetic innervation in this disorder in individuals with carotid sinus syndrome, asymptomatic carotid sinus hypersensitivity and controls without carotid sinus hypersensitivity.
  
  
  METHODS
  Consecutive patients diagnosed with carotid sinus syndrome at a specialist falls and syncope unit were recruited. Asymptomatic carotid sinus hypersensitivity and non-carotid sinus hypersensitivity control participants recruited from a community-dwelling cohort. Cardiac sympathetic innervation was determined using Iodine-123-metaiodobenzylguanidine (123-I-MIBG) scanning. Heart to mediastinal uptake ratio (H:M) were determined for early and late uptake on planar scintigraphy at 20 minutes and 3 hours following intravenous injection of 123-I-MIBG.
  
  
  RESULTS
  Forty-two subjects: carotid sinus syndrome (n = 21), asymptomatic carotid sinus hypersensitivity (n = 12) and no carotid sinus hypersensitivity (n = 9) were included. Compared to the non- carotid sinus hypersensitivity control group, the carotid sinus syndrome group had significantly higher early H:M (estimated mean difference, B = 0.40; 95% confidence interval, CI = 0.13 to 0.67, p = 0.005) and late H:M (B = 0.32; 95%CI = 0.03 to 0.62, p = 0.032). There was, however, no significant difference in early H:M (p = 0.326) or late H:M (p = 0.351) between the asymptomatic carotid sinus hypersensitivity group and non- carotid sinus hypersensitivity controls.
  
  
  CONCLUSIONS
  Cardiac sympathetic neuronal activity is increased relative to age-matched controls in individuals with carotid sinus syndrome but not those with asymptomatic carotid sinus hypersensitivity. Blood pressure and heart rate measurements alone may therefore represent an over simplification in the assessment for carotid sinus syndrome and the relative increase in cardiac sympathetic innervation provides additional clues to understanding the mechanisms behind the symptomatic presentation of carotid sinus hypersensitivity.
authors.affiliation: Ageing and Age-Associated Disorders Research Group, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Maw Pin
authors.initials: MP
authors.lastname: Tan
authors.affiliation: Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom.
authors.forename: Alan
authors.initials: A
authors.lastname: Murray
authors.affiliation: Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom.
authors.forename: Terry
authors.initials: T
authors.lastname: Hawkins
authors.affiliation: Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom; Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Chadwick
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom; Falls and Syncope Service, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.
authors.forename: Simon R J
authors.initials: SR
authors.lastname: Kerr
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom; Falls and Syncope Service, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.
authors.forename: Steve W
authors.initials: SW
authors.lastname: Parry
mesh_terms: D019797:3-Iodobenzylguanidine / Q000378:metabolism*; D000368:Aged; D000369:Aged, 80 and over; D002346:Carotid Sinus / Q000000981:diagnostic imaging* / Q000473:pathology; D016022:Case-Control Studies; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D006967:Hypersensitivity / Q000000981:diagnostic imaging* / Q000473:pathology; D007457:Iodine Radioisotopes / Q000378:metabolism*; D008297:Male; D008482:Mediastinum / Q000000981:diagnostic imaging; D008875:Middle Aged; D015999:Multivariate Analysis; D011877:Radionuclide Imaging; D012044:Regression Analysis
chemical_list: D007457:Iodine Radioisotopes; D019797:3-Iodobenzylguanidine