Circadian variation in thrombolytic response to recombinant tissue-type plasminogen activator in acute myocardial infarction
To investigate the existence of a circadian variation in thrombolytic response to either intravenous streptokinase or recombinant tissue-type plasminogen activator (rt-PA), time of symptom onset, time of treatment and angiographically documented coronary reperfusion were analyzed in 48 patients randomly assigned to thrombolytic treatment in the early stages of acute myocardial infarction (AMI). There were no statistically significant differences between streptokinase and rt-PA treated patients in lysis rates at any time interval or combination of time intervals (p > .05); although a trend favoring successful lysis with streptokinase in the morning hours was observed. Patients receiving streptokinase were as likely to achieve coronary reperfusion regardless of the time interval of treatment initiation (p > .05). However, patients treated with rt-PA between 12 midnight and 12 noon were 4 times less likely to reperfuse than patients treated during other time intervals (p = .0062). There were no significant differences between rt-PA treatment groups in gender, age, lag time to treatment, site of infarction, risk factors for coronary artery disease or use of beta blockers and/or nitrates. The underlying mechanism for a circadian variation in thrombolytic response to rt-PA in the setting of AMI remains undefined but may involve similar variations in thrombogenic potential and systemic fibrinolytic capacity. Further investigation of this area is warranted.
