Occlusion vs Nonocclusion MI – Rethinking NSTEMI

April 30, 2021

Written by Andy Hogan

Spoon Feed
A novel paradigm to classify acute MI based on the presence or absence of coronary occlusion—rather than on EKG evidence of ST-segment elevation alone—may identify NSTEMI patients who would benefit from emergent percutaneous coronary intervention.

Why does this matter?
Most patients diagnosed with NSTEMI in the emergency department are admitted for medical management and delayed cardiac catheterization. The occlusion MI (OMI) vs. nonocclusion MI (NOMI) paradigm may identify a subgroup of NSTEMI patients who deserve emergent cath lab activation.

Rating caths & clogs
This retrospective chart review was performed on a cohort of consecutively enrolled patients presenting to a single academic ED with symptoms concerning for ACS. 467 patients were classified as having either occlusion MI (OMI) or nonocclusion MI (NOMI) based on: angiographically confirmed coronary lesion with TIMI 0-2 flow, highly elevated peak troponin level with new wall motion abnormalities on echo, or pre-cath EKG showing STEMI.

A composite outcome of pre-cath cardiac arrest, in-hospital mortality, and discharge to hospice was found to be similar between STEMI(+) OMI and STEMI(-) OMI groups and significantly lower in the NOMI group. Mean time to cath for the STEMI(-) OMI group, however, was 437 minutes compared with 41 minutes for the STEMI(+) OMI group. The authors theorize that earlier PCI for STEMI(-) OMI patients with “the same angiographic disease as” STEMI(+) OMI patients might improve outcomes.

Importantly, the retrospective criteria used to define STEMI(-) OMI are not easily detectable in the acute setting (see Another Spoonful below to learn more). Furthermore, cath lab activation without STEMI on EKG occurs solely at the discretion of an interventional cardiologist in most settings. Without clear evidence of worse outcomes for STEMI(-) OMI patients compared to the STEMI(+) group, this study is unlikely to change cath lab activation protocols. Nevertheless, future research on the OMI/NOMI paradigm may help identify NSTEMIs that would benefit from emergent PCI.

Another Spoonful

• You really must read The OMI Manifesto, a collaboration between Dr. Smith’s ECG blog and EMCrit. There is a one-page cheat sheet of ECGs that should prompt cath lab activation.

• REBEL EM did an outstanding summary of this OMI/NOMI article as well if you want all the details.

Source
Comparison of the ST-Elevation Myocardial Infarction (STEMI) vs. NSTEMI and Occlusion MI (OMI) vs. NOMI Paradigms of Acute MI. J Emerg Med. 2021;60(3):273-284. doi:10.1016/j.jemermed.2020.10.026