title: Sympathetic nerve activity in the congenital long-QT syndrome.
abstract: BACKGROUND
  Patients with congenital long-QT syndrome (LQTS) are susceptible to life-threatening arrhythmias. The sympathetic nervous system may have an important triggering role for cardiovascular events in LQTS. We therefore examined measurements of sympathetic neural traffic in patients with LQTS and matched control subjects.
  
  
  RESULTS
  Twelve patients with congenital LQTS and 12 healthy volunteers matched for age, sex, and body mass index were studied. Heart rate, respiration, blood pressure, and sympathetic nerve activity to the skeletal muscle blood vessels (muscle sympathetic nerve activity) and to the skin (skin sympathetic nerve activity) were monitored and recorded continuously. Resting heart rate (P=0.03), muscle sympathetic nerve activity burst rate (P=0.008), and burst incidence (P=0.02) were lower in patients with LQTS than in control subjects. However, skin sympathetic nerve activity was very similar in patients with LQTS and control subjects. Spectral analysis of RR variability showed a decreased low-frequency component, an increased high-frequency component, and a decrease in the ratio of the low-frequency component to the high-frequency component in patients with LQTS (P=0.01).
  
  
  CONCLUSIONS
  LQTS is associated with a selective reduction in sympathetic drive to muscle blood vessels and perhaps also to the heart.
authors.affiliation: Mayo Clinic, Rochester, Minn 55905, USA.
authors.forename: Abu S M
authors.initials: AS
authors.lastname: Shamsuzzaman
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
authors.forename: Tomas
authors.initials: T
authors.lastname: Kara
authors.forename: Paola
authors.initials: P
authors.lastname: Lanfranchi
authors.forename: Virend K
authors.initials: VK
authors.lastname: Somers
mesh_terms: D000328:Adult; D001808:Blood Vessels / Q000294:innervation; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000151:congenital* / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation; D012867:Skin / Q000294:innervation; D013564:Sympathetic Nervous System / Q000503:physiopathology*