inappropriate atrial sinus tachycardia (IAST)

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Inappropriate atrial sinus tachycardia (IAST)

  • IAST is a clinical syndrome with a relative or absolute increase in sinus rate out of proportion to physiological need
    • general agreement among clinicians and investigators that a heart rate exceeding 90-100 beats per minute (bpm) at rest or with minimal physiologic challenge is "inappropriate" (1)
      • P-wave morphology during tachycardia is nearly identical to that during normal sinus rhythm (1)
      • on a 24-hour Holter monitor, the mean heart rate exceeds 95 bpm, a daytime resting heart rate exceeds 95 bpm, or an increase in sinus rate from supine to upright position of more than 25-30 bpm
    • clinical manifestations of this syndrome are diverse, and the epidemiology of this patient population is not well defined
      • patients are primarily young women (15-50 years of age)
      • association of IAST patients with health professional workers has been recognized (1)
      • common symptoms include palpitations, light-headedness, presyncope, syncope, exercise intolerance, easy fatigue, dyspnoea, chest pain, myalgia, headache, abdominal discomfort, anxiety, and depression
    • underlying mechanisms of IAST are not well defined
      • proposed mechanisms include:
        • enhanced automaticity of the sinus node, altered autonomic responses manifest as increased sympathetic tone, either directly or via sympathetic receptor hypersensitivity or blunted parasympathetic tone, and impairment of baroreflex sensitivity


  • 1. Pacing Clin Electrophysiol. 2005 Oct;28(10):1112-21.
  • 2. Castellanos A et al. Heart rate variability in inappropriate sinus tachycardia. Am J Cardiol 1998; 82: 531–534.
  • 3. Sgarbossa EB et al. Autonomic imbalance in patients with inappropriate sinus tachycardia. (abstract) Am Coll Cardiol 1995; 25: 193A.

Last reviewed 01/2018