How to use T wave morphology to recognize NSTEMI
Serial 12-lead ECGs are used to recognize the difference between STEMI and NSTEMI in a patient with chest discomfort
You call in the following report to the destination ED en route to the nearest hospital:
"We are 15 minutes out with a 57-year-old male who was awakened from sleep with retro-sternal chest pain. He reports that this pain is similar to his prior MI five years ago which was treated by PCI and stent. Since then he has been well and managed medically with metoprolol, enalapril, glucophage, aspirin and simvastatin.
He has never had to use nitroglycerin since his prior MI and he denies recent exertional or rest chest pain before this AM. He reports that his pain was also accompanied by slight dyspnea and sweating.
We established an IV, gave aspirin and two sublingual nitroglycerins and the patient became pain-free. We then applied one inch of nitroglycerin paste to the chest and he remains pain-free.
His vital signs have remained normal throughout. We are concerned that he has dynamic changes on his EKG that coincide with his symptoms and so are bringing him to your facility as you have a cath lab team on-call.
The EKG Club experts created this case for these learning objectives:
- Basic: Identify acute coronary syndrome and appropriate initial treatment.
- Intermediate: Identify the EKG features that indicate the need for additional cardiac testing.
- Advanced: Identify and treat a symptomatic patient with T wave pseudo-normalization.
The crew's initial treatment is consistent with the consideration of a NSTEMI. The patient presented a 12-lead EKG that was not suggestive for ischemia, but displayed clinical signs of an acute coronary syndrome. The second 12-lead EKG, taken after the patient reported being pain-free, revealed negative T waves in the inferior leads (II, III and aVF) and the low lateral leads (V5 and V6). The normal complexes during the pain/ischemic period and inverted T waves during treatment (and pain relief) are of great relevance and are called T wave pseudo-normalization.
Inverted T waves most likely reflect this patient's baseline. When the T waves were not elevated nor inverted (in the first EKG) it may give the false appearance of being normal when in fact they were not. By acquiring serial EKGs and noting the subtle changes that occurred during an improvement in the patient’s pain, we can be confident this pain is of a cardiac origin.
The ultimate treatment regimen will depend on the outcome of additional serial EKG tests, cardiac enzyme testing and possibly an echocardiogram. This patient will probably not go straight to the cardiac catheterization laboratory, but will likely have a positive outcome.
Additional Teaching Points:
- Advanced Study of Medicine — http://www.jhasim.com/files/articlefiles/pdf/ASIM_6_6Bp483_490_R1.pdf
- An interesting Romanian thesis abstract (unsigned) discussion of T-wave pseudo normalization — http://www.umftgm.ro/doctorat/dragan.pdf
- “Exercise-induced T-wave normalization predicts recovery of regional contractile function after anterior myocardial infarction” — http://eurheartj.oxfordjournals.org/cgi/content/abstract/19/3/420
- "Recognition of Acute Coronary Syndrome in the Clinical Setting" — http://www.scpcp.org/library/pdf/Cooper_ECG_for_ACS.doc