Clinical evaluation is better: myoglobin estimation used singly as a discriminant for early acute myocardial infarction does not well identify patients who will benefit from thrombolytic therapy

We have examined the use of serum myoglobin concentration in the management of cases of suspected acute myocardial infarction (AMI). In a series of 51 patients myoglobin, used as a discriminant, correctly identified 97% (28/29) of cases as AMI with one false positive. Initial clinical judgement based on history, examination and the electrocardiogram correctly identified 66% (19/29) of cases with one false positive. These patients were given streptokinase. However, in these further identified AMI patients, 78% (7/9) had small enzyme rises with non-Q wave infarction and/or non-ST elevation and therefore may not have benefited from thrombolytic therapy in contrast to the Q wave/raised ST segment infarcts with large enzyme rises identified by clinical means. Enthusiasm for myoglobin estimation, where used as a discriminant for AMI, as a direct pointer to thrombolysis in the early diagnosis of AMI should be tempered by this finding.