title: Prevalence, characteristics and natural course of inappropriate sinus tachycardia.
abstract: OBJECTIVE
  To study the prevalence, characteristics and natural course of inappropriate sinus tachycardia (IST).
  
  
  RESULTS
  The prevalence and characteristics of IST were evaluated in a random sample of 604 middle-aged subjects. Seven of the subjects (1.16%) fulfilled the contemporary diagnostic criteria of IST. The systolic (147+/-11 mmHg vs. 130+/-13 mmHg, P<0.001) and diastolic ambulatory blood pressures (92+/-7 mmHg vs. 81+/-8 mmHg, P<0.001) were higher among the subjects with IST than among the controls. The other laboratory, echocardiographic and personality measurements, with the exception of the hostility score (10+/-2 vs. 8+/-3, P<0.001), revealed no differences between the groups. The natural course and prognosis of the disorder was assessed among the subjects fulfilling the IST criteria and nine previously diagnosed IST patients. During a mean follow-up of 6.0+/-2.4 years, none of the subjects developed any clinical or echocardiographic evidence of structural heart disease despite ongoing palpitations, and there was no significant reduction in the 24-h average HR (9+/-2 bpm vs. 89+/-8 bpm, P=0.204).
  
  
  CONCLUSIONS
  The prevalence of IST in a middle-aged population was higher than previously assumed. Despite the chronic nature of the disorder, the prognosis of IST was benign. The causal relationship between IST and hypertension and/or hostile personality type remains speculative.
authors.affiliation: Department of Internal Medicine, Division of Cardiology, University of Oulu, P.O. Box 5000, FIN-900014, Finland.
authors.forename: Aino-Maija
authors.initials: AM
authors.lastname: Still
authors.forename: Pekka
authors.initials: P
authors.lastname: Raatikainen
authors.forename: Antti
authors.initials: A
authors.lastname: Ylitalo
authors.forename: Heikki
authors.initials: H
authors.lastname: Kauma
authors.forename: Markku
authors.initials: M
authors.lastname: Ikäheimo
authors.forename: Y
authors.initials: Y
authors.lastname: Antero Kesäniemi
authors.forename: Heikki V
authors.initials: HV
authors.lastname: Huikuri
mesh_terms: D016009:Chi-Square Distribution; D005260:Female; D005387:Finland / Q000453:epidemiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011379:Prognosis; D018709:Statistics, Nonparametric; D013616:Tachycardia, Sinus / Q000453:epidemiology* / Q000503:physiopathology*