Circadian variations of onset of acute myocardial infarction and efficacy of thrombolytic therapy

J Am Coll Cardiol. 1996 Mar 15;27(4):774-8. doi: 10.1016/0735-1097(95)00552-8.


Objectives: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Circadian Rhythm*
  • Cohort Studies
  • Drug Resistance
  • Female
  • Humans
  • Male
  • Middle Aged
  • Myocardial Infarction / drug therapy
  • Myocardial Infarction / physiopathology*
  • Plasminogen Activators / therapeutic use
  • Retrospective Studies
  • Thrombolytic Therapy*
  • Time Factors
  • Tissue Plasminogen Activator / therapeutic use
  • Urokinase-Type Plasminogen Activator / therapeutic use


  • Plasminogen Activators
  • Tissue Plasminogen Activator
  • Urokinase-Type Plasminogen Activator