Ruling out acute myocardial infarction early with two serial creatine kinase-MBmass determinations

Aims We studied the diagnostic value for acute myocardial infarction of serial creatine kinase-MBmass measurements on admission and at 7 h after the onset of symptoms. Methods and Results Patients presenting to our chest pain unit with symptoms of <5-h duration were eligible. Patients were kept under observation at least until 12h after onset of symptoms. Blood samples were drawn on admission and 7 and 10 h after onset of symptoms. Creatine kinase-MBmass >7.0 mu g.l(-1) (upper reference limit for acute myocardial infarction), or an increase >2.0 mu g.l(-1) (reference change value) between admission and at 7 h was considered abnormal. Of a total of 470 patients, 248 patients had acute myocardial infarction: 100 out of the 248 patients had a single creatine kinase-MBmass >7.0 mu g.l(-1) on admission (sensitivity 40%, 95% CI:34-46%), 234/248 patients at 7h(sensitivity 94%, 95% CI:91-97%), and 240/248 at 10 h (sensitivity 97%, 95% CI:94-99%). At 7 h, 246/248 patients had either a single creatine kinase-MB >7.0 mu g.l(-1) or a significant increase between admission and 7 h (sensitivity 99%, 95% CI:98-100%). Of 222 patients without acute myocardial infarction, 214 had a normal serial creatine kinase-MBmass (specificity 96%, 95% CI:93-98%). Conclusion In patients with symptoms of <5-h duration, acute myocardial infarction can be ruled out using serial creatine kinase-MBmass taken on admission and at 7 h.