title: Differences in autonomic nerve function in patients with silent and symptomatic myocardial ischaemia.
abstract: BACKGROUND
  Autonomic neuropathy provides a mechanism for the absence of symptoms in silent myocardial ischaemia, but characterisation of the type of neuropathy is lacking.
  
  
  OBJECTIVE
  To characterise and compare autonomic nerve function in patients with silent and symptomatic myocardial ischaemia.
  
  
  RESULTS
  The Valsalva manoeuvre, heart rate variation (HRV) in response to deep breathing and standing, lower body negative pressure, isometric handgrip, and the cold pressor test were performed by patients with silent (n = 25) and symptomatic (n = 25) ambulatory ischaemia and by controls (n = 21). No difference in parasympathetic efferent function between patients with silent and symptomatic ischaemia was recorded, but both had significantly less HRV in response to standing than the controls (p < 0.005 for silent and p < 0.01 for symptomatic). Patients with silent ischaemia showed an increased propensity for peripheral vasodilatation compared with symptomatic patients (p < 0.02) and controls (p < 0.04). Impaired sympathetic function was found in patients with pure silent ischaemia (n = 4) compared with the remaining patients with silent ischaemia whose pain pathways were presumed to be intact.
  
  
  CONCLUSIONS
  Patients with silent ischaemia and pain pathways presumed to be intact have an enhanced peripheral vasodilator response, and if this applied to the coronary vasculature it could provide a mechanism for limiting ischaemia to below the pain threshold. Patients with pure silent ischaemia have evidence of sympathetic autonomic dysfunction.
authors.affiliation: Cardiac Department, St Thomas' Hospital, London.
authors.forename: C F
authors.initials: CF
authors.lastname: Shakespeare
authors.forename: D
authors.initials: D
authors.lastname: Katritsis
authors.forename: A
authors.initials: A
authors.lastname: Crowther
authors.forename: I C
authors.initials: IC
authors.lastname: Cooper
authors.forename: J D
authors.initials: JD
authors.lastname: Coltart
authors.forename: M W
authors.initials: MW
authors.lastname: Webb-Peploe
mesh_terms: D001341:Autonomic Nervous System / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology*; D010991:Plethysmography; D013564:Sympathetic Nervous System / Q000503:physiopathology; D014636:Valsalva Maneuver; D014664:Vasodilation / Q000502:physiology