The activated partial thromboplastin time in early diagnosis of myocardial infarction.

Intracoronary thrombosis is fundamental to the pathogenesis of acute myocardial infarction (MI), yet few studies have examined the diagnostic value of routine coagulability markers, such as the activated partial thromboplastin time (aPTT), in patients with chest pain. We hypothesized that the initiation of thrombosis early in MI would shorten the aPTT, and conducted a retrospective cohort study of patients admitted with a diagnosis of chest pain through the emergency department of one community hospital between 1 January and 30 August 1998. Patients were diagnosed as MI positive or negative based on World Health Organization (WHO) criteria. The aPTT obtained on arrival (prior to anticoagulation therapy) was retrieved from the electronic medical record. Of 120 eligible patients (49% female, mean age 63.7 years), 27 (23%) were diagnosed with MI. Patients with an aPTT <or= control (n = 73, 61%) were significantly more likely to be diagnosed with MI than those with an aPTT > control (RR = 2.83, 95% confidence interval 1.15 to 6.96, P = 0.013). A shortened aPTT (<or= control) on presentation in patients with chest pain is associated with increased risk of acute MI. This information is available before other serum markers of MI, and may facilitate early treatment decisions. Further study is warranted.