Serial Troponin for Atypical Symptoms? – PART III
In general, the literature suggests that elderly patients who present with atypical chest pain should receive at least two troponins for several reasons: 1) though there are many practical reasons to order a single troponin measurement in the ED, the practice of doing so for patients at risk for ACS is not yet supported by rigorous evidence; and 2) elderly patients with atypical presentations (particularly painless shortness of breath) are at risk of worse outcomes and under-treatment compared to patients with classic ischemic chest pain. This being said, there are studies to support the utility of serial troponins at shorter intervals (3-4 hours in particular, but even a 1-hour interval can be justified if a clear time of onset is established). A compromise might be to continue to order serial troponins, but recognize that you don’t always need to adhere to the 6 hour guideline.
It is also important to keep in mind that cardiac troponin I has high sensitivity and negative predictive value, which is counterbalanced by low specificity and limited positive predictive value. This means that a positive initial troponin shouldn’t automatically pigeonhole the patient into a Cardiology consult or admission. Remember that ACS is a clinical diagnosis, and troponin is only a risk assessment tool that does not replace clinical symptoms, EKG, or history. Elderly patients, particularly those with preexisting conditions such as renal failure, may have higher baseline serum troponin levels to begin with, or an alternate explanation for an acute increase in serum troponin levels. A broader differential and some more critical thinking is definitely warranted in these cases. Again, don’t forget the clinical picture: a stable ESRD patient with normal vital signs, no EKG changes, and no acute distress is unlikely to be undergoing an acute MI even with elevated initial troponin levels. On the other hand, this does not mean that a second troponin 3-4 hours later is not warranted, since atypical presentations are still possible and easy to miss.
If it seems like there’s no clear answer to this question, that’s because there isn’t! If you’re reading this and have objections or musings to share, please don’t hesitate to comment below.
A big thanks to Dr. Sumintra Wood for inspiring this series of Pearls.