BradyCardia: False Comfort in a Normal Troponin : Emergency Medicine News

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BradyCardia

BradyCardia

False Comfort in a Normal Troponin

Pregerson, Brady MD

Emergency Medicine News 45(1):p 14, January 2023. | DOI: 10.1097/01.EEM.0000911912.07201.c8
    FU1-12
    Figure:
    ECG, troponin, STEMI, LAD, pulmonary embolism, PE, ST elevation, occlusion MI
    FU2-12
    Figure

    A man in his mid-40s had chest pain that had started about an hour before his arrival in the ED. He had been at work when the pain suddenly developed. He also had difficulty breathing.

    He had had a similar milder episode that had lasted about 20 minutes the day before. He reported no syncope, palpitations, leg swelling or pain, fever, cough, or other symptoms but said he was a smoker. His vital signs were normal, as was the physical exam, but he appeared pretty uncomfortable.

    An ECG was done, and the computer read it as a normal sinus rhythm of 66, incomplete right bundle branch block, and septal myocardial infarction, possibly acute.

    What is the most likely cause of the ECG findings in this patient? Anxiety, a blood clot (pulmonary embolism), a nonocclusion MI, or an occlusion MI?

    ECG Analysis

    The ECG showed a broad P-wave best appreciated in the lateral leads and obvious ST elevation in V1-V4 with ST depression in the inferior leads and V6. The T-wave in aVL was hyperacute, and ST elevation and an R-wave were seen in lead aVR. My assessment was that the patient was having a STEMI/OMI and needed emergent PCI.

    I asked Stephen W. Smith, MD, of Dr. Smith's ECG Blog (http://bit.ly/DrSmithsECGBlog) for his read, and he said the ECG was diagnostic of a proximal LAD occlusion until proven otherwise and that the patient needed to go emergently for PCI. ST elevation in V1 (and usually aVR) along with ST depression in V5 and V6 signify transmural ischemia of the septum and possibly the base (top) of the ventricle, he said. The occlusion is not only proximal to the first diagonal (leading to high lateral OMI) but also proximal to the first septal perforator.

    Dr. Smith said he and Pendell Meyers, MD, an associate editor of the blog, coined the term precordial swirl pattern for this morphology. In this case, the ST elevation meets the STEMI criteria, but it often does not. See other examples and mimics of precordial swirl at http://bit.ly/3EfWElI.

    Case Lessons

    Anxiety should always be a diagnosis of exclusion and should not cause ECG changes beyond tachycardia. Pulmonary embolism is not likely to cause this kind of ST elevation. A NOMI is incorrect in this case, and an OMI is the right diagnosis.

    The initial troponin I was undetectable, which should not be a surprise in the first few hours after OMI onset. You can get false-negative results in unstable angina and in the first two to four hours or more of an OMI or STEMI even with high-sensitivity troponins. (JAMA Cardiol. 2020;5[11]:1302; http://bit.ly/3UKB0wZ.) Catheterization showed a 100 percent occluded proximal LAD lesion.

    The troponin will often be normal for the first few hours of an occlusion MI, which is when the benefit from cath is the highest because further damage can be avoided by PCI. Waiting for the troponin level to be abnormal in patients with ongoing ischemic symptoms and concerning ECGs is at the patient's peril.

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    Dr. Pregersonis an emergency physician with Palomar and Tri-City medical centers in San Diego. He is the author of the Emergency Medicine 1-Minute Consult, the 8-in-1 Emergency Department Quick Reference, the A-to-Z Emergency Pharmacopoeia & Antibiotic Guide, and Think Twice: More Lessons from the ER. Follow him on Twitter@EM1MinuteGuru, and visit his websiteshttps://www.erpocketbooks.com/andhttps://em1minuteconsult.com. Read his past columns athttp://bit.ly/BradyCardiaEMN.

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