title: Relationships between the QTc interval and cardiovascular, stroke, or sudden cardiac mortality in the general Japanese population.
abstract: BACKGROUND
  We attempted to evaluate whether the relationship between the QTc interval and mortality (including sudden cardiac death) is linear or J-shaped in the general Japanese population, who tend to be at greater risk of strokes than cardiac events.
  
  
  METHODS
  We classified 10,804 subjects according to their Bazett QTc interval quartiles (determined by electrocardiography) at the baseline and followed them up for a mean period of 141.9±28.3 months (127,712 person-years).
  
  
  RESULTS
  In total, 878 subjects died during the study period, including 104 from cardiovascular events, 100 from stroke, and 46 from sudden cardiac death. In a Cox proportional hazards regression model adjusted for conventional cardiovascular risk factors, the risk of cardiovascular mortality increased progressively with the QTc interval quartile [Q2, hazard ratio (HR)=0.94 (0.43-2.03); Q3, HR=1.11 (0.53-2.34); Q4, HR=2.21 (1.12-4.36); HR are vs. Q1]. A parallel analysis found that the risk of stroke mortality was marginally increased in the highest Bazett QTc interval quartile [HR=1.93 (0.97-3.85)]. On the other hand, the risk of sudden cardiac death exhibited a J-shaped relationship with the Bazett QTc interval quartile [Q1, HR=8.58 (1.07-69.05); Q3, HR=7.17 (0.88-58.73); Q4, HR=13.18 (1.72-101.03); HR are vs. Q2].
  
  
  CONCLUSIONS
  In the general Japanese population, cardiovascular and stroke mortality increase progressively with the Bazett QTc interval quartile, while the risk of sudden cardiac death exhibits a J-shaped relationship with the latter variable.
authors: Division of Cardiovascular Medicine, Department of Medicine, Jichi Medical University, School of Medicine, Tochigi, Japan. Electronic address: george@jichi.ac.jp.
authors: Joji
authors: J
authors: Ishikawa
authors: Division of Community and Family Medicine, Center for Community Medicine, Jichi Medical University, Tochigi, Japan.
authors: Shizukiyo
authors: S
authors: Ishikawa
authors: Division of Cardiovascular Medicine, Department of Medicine, Jichi Medical University, School of Medicine, Tochigi, Japan.
authors: Kazuomi
authors: K
authors: Kario
mesh_terms: D000328:Adult; D002318:Cardiovascular Diseases / Q000209:etiology / Q000401:mortality*; D016757:Death, Sudden, Cardiac / Q000453:epidemiology* / Q000209:etiology; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008133:Long QT Syndrome / Q000150:complications*; D008297:Male; D016016:Proportional Hazards Models; D012307:Risk Factors; D020521:Stroke / Q000209:etiology / Q000401:mortality*
keywords: Cardiovascular death; Myocardial infarction; QTc interval; Stroke; Sudden cardiac death