Cardiac troponins are proteins that are found in heart muscle and play a role in the contraction of the heart muscle. If heart muscle is in someway damaged or injured, then cardiac troponins are leaked into the blood and can therefore be measured in the blood stream. They have therefore become exceptionally useful markers of cardiac cell injury and this is why anyone who presents to hospital with symptoms of chest discomfort will have a blood test to measure troponin to look for objective evidence of cardiac damage. The original troponin assays were not very sensitive and any detectable troponin in the blood was considered abnormal. As the assays for measuring troponins in the blood have improved, we now use high sensitivity troponin assays which are extremely sensitive at picking up Troponin into the blood and we are now realising that even healthy and normal people may have tiny amounts of troponin in their blood. However to find a troponin value which is above the 99% centile value is definitely abnormal as is a rapidly increasing troponin from baseline. The finding of a very high or rapidly rising troponin in a patient complaining of acute chest discomfort or a very abnormal ECG is all that is needed to confirm a diagnosis of a heart attack.
Here are 5 facts that you may find useful to know about Troponin:
- Troponin levels in the blood seem to rise 2-3 hours after heart muscle damage so if the troponin is done too early it may be falsely negative
- Troponin levels may remain elevated in the blood stream for upto 1-2 weeks after the event. So if you had chest pains 3 days ago, it may still be worth having the blood test. If the pain was 3 weeks ago, then any troponin that mayy have leaked into the blood stream may no longer be present. If you have had damage to your heart and your troponin level is falling and if yyou have more pain after a week and the troponin level increases again then it indicates a new event.
- The presence of an elevated troponin points to a significantly higher likelihood of the patient dying, suffering a major heart attack or requiring a procedure on the heart (bypass or stents) within the next 14 days and therefore such patients should stay in hospital and undergo the necessary investigations and treatment as an inpatient. The absence of an elevated troponin points to a lower risk patient (but not no risk) and therefore these patients still need investigations but not as an emergency.
- The peak level of troponin seems to correlate with the magnitude of heart damage if no intervention is carried out to prevent further damage. In general people with higher troponin rises will be left with weaker hearts if nothing is done. Nevertheless any significant increase in troponin indicates a higher risk patient.
- If the troponin is normal then that is a good indicator that there has been no damage. If the troponin is elevated it does not always mean that the patient had had a heart attack. There are several other situations in which the troponin mayy be falsely elevated. These include:
- Takotsubo syndrome
- Pulmonary embolism (interestingly in these patients the troponin levels settle down in about 440 hours as compared to the 1-2 weeks with a heart attack
- Trauma (such as cardioversion or defibrilation)
We also see it in patients who have had bad infections or who have been critically unwell. Troponin rises may also be seen in patients who already have pre-existing structural heart disease such as hypertrophic cardiomyopathy or even patients who have had fast heart rhythm disturbances such as AF
- In the appropriate patient, an elevated troponin indicates heart damage and should prompt urgent inpatient further investigations.
- A normal troponin indicates low risk (but not no risk)
- Troponins may be falsely elevated in certain situations and do not always point to a diagnosis of a heart attack. When elevated, they should certainly prompt investigation for an alternative aetiology after the heart has been investigated.
Tags: Troponin; high sensitivity troponin; Heart enzymes; heart attack