Can troponin levels diagnose an MI?
QI have been seeing patients discharged as non ST elevation MI (NSTEMI) on the basis of a single troponin blood test alone. What is the best plan to prove it was cardiac beyond any doubt?
AThe Joint ESC/ACC Committee for the Redefinition of Myocardial Infarction emphasised use of serum troponins as indicators of myocardial necrosis. Troponins are accurate in identifying myocardial necrosis if tested 12 hours post-injury with prognostic implications.
But in establishing the diagnosis, cardiac troponins are used in conjunction with appropriate clinical features and electrocardiographic changes; indeed, myocardial injury of diverse origins (myocarditis, trauma, or cardioversion) may also cause release of troponins, and should be distinguished on clinical grounds from the more common form of NSTEMI secondary to coronary atherosclerosis.
In cases of uncertainty, other non-invasive tests, such as a myocardial perfusion scanning, or invasive tests such as cardiac catheterisation may help to confirm a cardiac origin.
Dr Gregory Lip is professor of cardiovascular medicine at the university department of medicine,
City Hospital, Birmingham