title: Circadian variations of onset of acute myocardial infarction and efficacy of thrombolytic therapy.
abstract: OBJECTIVE
  The present study investigated whether the onset of acute myocardial infarction and resistance to thrombolysis have similar circadian variations.
  
  
  BACKGROUND
  Circadian variations of the onset of acute myocardial infarction and resistance to thrombolysis in the early morning have been reported. Some studies have also reported a secondary peak incidence in late evening; however, it is not known whether the resistance to thrombolysis has a similar circadian variation in these patients.
  
  
  METHODS
  Six hundred eight Japanese patients with an acute myocardial infarction were the subjects of the study. Two hundred forty-four of the 608 patients were treated with thrombolysis within 12 h of the onset of symptoms. One hundred thirteen patients received urokinase, and 131 patients received tissue-type plasminogen activator (t-PA) over 60 min. Patency of the infarct-related artery, the primary end point of the study, was evaluated at 60 min after the initiation of thrombolytic therapy, and Thrombolysis in Myocardial Infarction (TIMI) grade 0, 1 or 2 was defined as resistant to thrombolysis.
  
  
  RESULTS
  The onset of acute myocardial infarction and resistance to thrombolysis showed circadian variations with early morning and late evening peaks (p<0.001 and p<0.05, respectively). These circadian patterns showed similar distributions as evaluated with Spearman's method (r=0.70, p<0.05), although resistance to thrombolysis showed a phase difference of about 2 h earlier than the infarction incidence. The circadian variation of the resistance to thrombolysis was independent of the types of thrombolytic agents (urokinase or t-PA).
  
  
  CONCLUSIONS
  These findings suggest that adjustment of treatment based on the time of the onset of symptoms may be warranted for the patients with acute myocardial infarction.
authors.affiliation: Osaka Mishima Critical Care Medical Center, Osaka Medical College, Takatsuki, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kono
authors.forename: H
authors.initials: H
authors.lastname: Morita
authors.forename: T
authors.initials: T
authors.lastname: Nishina
authors.forename: M
authors.initials: M
authors.lastname: Fujita
authors.forename: Y
authors.initials: Y
authors.lastname: Hirota
authors.forename: K
authors.initials: K
authors.lastname: Kawamura
authors.forename: A
authors.initials: A
authors.lastname: Fujiwara
mesh_terms: D000368:Aged; D002940:Circadian Rhythm; D015331:Cohort Studies; D004351:Drug Resistance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000188:drug therapy / Q000503:physiopathology*; D010960:Plasminogen Activators / Q000627:therapeutic use; D012189:Retrospective Studies; D015912:Thrombolytic Therapy; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000627:therapeutic use; D014568:Urokinase-Type Plasminogen Activator / Q000627:therapeutic use
chemical_list: D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator