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Breaking habits in medicine can be hard. Case in point: "trending troponin to peak" in patients with MI. Why is this done? Is it useful? You might be surprised at the answer. 1/ @NinoNJ @CianPMcCarthy @MGHMedicine @MGHHMU @MGHHeartHealth @chapdoc1 @HighSTEACS @troponinpapers
2/Why "trend troponin to peak" anyhow? Most do it to "size" the infarct; specifically, the concept is that the amount of troponin efflux from necrotic tissue is proportional to the size of the infarct.
But is this true? Is it accurate?
But is this true? Is it accurate?
3/In a very nice review (karger.com/Article/Fullte…) Hallen makes the important point that infarct size and troponin kinetics ARE modestly correlated (r values of 0.5-0.75), BUT best data are with STEMI. We don't need troponins to diagnose or estimate infarct size in STEMI.
4/What about NSTEMI? This is important, since most MIs we see lack ST elevation. Troponins are FAR less useful to estimate infarct size in NSTEMI, yet the tropo-mania (with endless measurements to reach the "peak") yet continues.
Why are they less useful in NSTEMI?
Why are they less useful in NSTEMI?
5/In part, the release kinetics in a STEMI--immediate washout after revascularization--are not mimicked in most NSTEMIs, who are taken for revascularization somewhat less rapidly. Thus, there's often slower rise to peak in NSTEMI, even if that peak is lower purely on that basis.
6/Troponin release is not linear--there's early efflux of the cytosol, followed by slow necrosis of the sarcomere, which can take up to 10-14 days. Thus, you need the area under the curve (AUC) to estimate size of injury. With rapid revasc in STEMI, peak and AUC are similar.
7/People assume peak value is sufficient to estimate the AUC, but the approach is not accurate in NSTEMI. So...what's the solution to size an infarct? We do it already...an echo, an LV gram, etc. IMO, serial troponin testing in MI for infarct size is a waste of time and money.
8/There are reasons to serially continue measuring troponin--if a patient has recurrent symptoms, if the diagnosis is in doubt (e.g. myocarditis, with its 'hang' of troponin results)--but almost always, if you have your diagnosis it should be 1 or 2 and done.
The end.
The end.
