Diagnostic performance of venous lactate on arrival at the emergency department for myocardial infarction.

OBJECTIVES To determine the sensitivity of the venous lactate level at presentation for acute myocardial infarction (AMI) in emergency department (ED) patients with chest pain. METHODS A prospective, double-blind observational study was done in a tertiary care ED. From January to April 2000, all consecutive patients presenting with chest pain were eligible. Lactate level was obtained on arrival and compared with two criterion standards for the diagnosis of AMI: the World Health Organization (WHO) and the Joint European Society of Cardiology/American College of Cardiology Committee (ESC/ACC) classifications. A lactate level greater than 1.50 mmol/L was considered positive. RESULTS Between January and April 2000, 718 patients were enrolled. By the WHO criteria, 64 patients suffered an AMI, of whom 59 had an elevated lactate level, yielding a sensitivity of 92% (95% CI = 86% to 99%), a specificity of 44% (95% CI = 40% to 48%), and a negative predictive value (NPV) of 98% (95% CI = 97% to 99%). For all patients presenting with more than two hours of chest pain (n=34), the lactate level was elevated. When using the ESC/ACC criteria, 100 patients sustained an AMI, of whom 88 had an elevated lactate level, yielding a sensitivity of 88% (95% CI = 82% to 94%), a specificity of 46% (95% CI = 42% to 50%), and an NPV of 96% (95% CI = 94% to 98%). CONCLUSIONS Venous lactate level at presentation is highly sensitive for the diagnosis of AMI, particularly in patients with more than two hours of chest pain. Given its limitations in specificity and ability to detect creatine kinase-MB-negative/troponin-positive microinfarcts, further research is needed to determine how lactate can complement other cardiac enzymes in risk-stratifying all acute coronary syndromes.