Résumé
Differentiating transient myocardial ischemia or angina from non-cardiac causes of chest pain is a major diagnostic challenge. Cardiac troponin I [cTnI] is sensitive and specific for the detection of myocardial damage but may not rise during reversible myocardial ischemia. Ischemia Modified Albumin [IMA] has recently been shown to be a sensitive and early biochemical marker of ischemia. We studied eighty-five patients presenting to the emergency department [ED] within 3 hours of acute chest pain. Blood samples were taken for IMA and cardiac troponin I, at presentation and then after 12 hours. Patients underwent standardized diagnostic procedures, and treatment. Results of IMA, cTnI were correlated with final diagnoses of non-ischaemic chest pain [NICP], unstable angina [UA] and acute myocardial infarction [AMI]. The sensitivity and specificity of IMA for the detection of myocardial ischemia were evaluated by ROC curve analysis. The mean absorbance value [ABSU] of IMA was significantly higher in patients with UA [0.6610.14 and 0.70 +/- 0.18] and those with AMI [0.70 +/- 0.19 and 0.74 +/- 0.22] when compared to individuals with NICP [0.48 +/- 0.11 and 0.50 +/- 0.13] [p < 0.001], both at admission and at the late 12 hours samples respectively. However, the mean ABSU value of IMA showed no significant difference between patients with UA and AMI [P > 0.05] both at admission and after 12 hours. When ROC curve was constructed to evaluate IMA-ABSU in NICP patients compared to all acute coronary syndrome [ACS] patients, the area under the curve was 0.85 [95% confidence interval [CI], 0.76-0.94], immediately after admission, and at cutoff value of 0.51 ABSU, sensitivity and specificity were 86% and 64% respectively. Nearly, the same results were obtained when NICP patients was compared with AMI patients and UA patients separately. While when we compared UA and AMI groups, the area under the curve was 0.6 [95% confidence interval [CI], 0.45-0.74], indicating a poor discrimination between these two groups. CTnI values showed a non-significant difference between patients with UA [1.6 +/- 0.7mnicrog/L] and NICP [1.3 +/- 0.3 microg/L], [P>0.05] at the time of admission, but after 12 hours, cTnI values were significantly higher in patients with UA [1.8 +/- 0.6microg/L] than NICP [1.3 +/- 0.5 microg/L], [P < 0.05]. On the other hand, patients with AMI showed significant increase of cTnI both at admission [1.8 +/- 0.8 microg/L] and 12 hours later [2.9 +/- 0.9 microg/L] when compared to NICP group [p < 0.01 and 0.001 respectively]. IMA is highly sensitive for the early diagnosis of myocardial ischemia in patients presenting with symptoms of acute chest pain