A single blood test to rule out myocardial infarction?

The release into the circulation of troponin I and T signals irreversible injury to cardiac myocytes and is central to the diagnosis of myocardial infarction.1 Conventional (non-high sensitivity) troponin assays are optimally sensitive 10-12 hours after the onset of symptoms, and in patients presenting with cardiac chest pain a rise or fall in troponin levels during this period—with at least one value exceeding the upper reference limit—is diagnostic of myocardial infarction.

In practice, troponin plays a bystander role in the diagnosis of ST segment elevation myocardial infarction (STEMI), the electrocardiogram (ECG) providing sufficient diagnostic certainty for emergency intervention. But in non-ST segment elevation myocardial infarction (NSTEMI) the ECG is non-diagnostic, and serial troponin testing is required to confirm the diagnosis. Because most patients attending emergency departments with chest pain do not have NSTEMI and can often be discharged safely, strategies that can rule out NSTEMI reliably and quickly to accelerate care pathways and relieve pressure on beds are urgently needed.2 The two linked papers (doi:10.1136/bmj.h15, doi:10.1136/bmj.g7873) are therefore timely in reporting the use of high sensitivity troponin assays to rule out myocardial infarction early, in …