BradyCardia: Don't Be Fooled by a Reassuring Stress Test : Emergency Medicine News

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BradyCardia

Don't Be Fooled by a Reassuring Stress Test

Pregerson, Brady MD

doi: 10.1097/01.EEM.0000898204.53578.87
    FU1-9
    Figure:
    ECG, stress test, acute coronary syndrome
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    Figure

    A patient in his mid-60s with a history of hypertension, hyperlipidemia, and diabetes mellitus presented to the hospital for chest pain radiating down his left arm. It had started approximately two hours before while he was at rest.

    A few days before that, he had had an episode of exertional chest pain without radiation while doing yard work. He said his current pain began radiating down his left arm and was associated with shortness of breath.

    The patient reported his pain at 3/10, and said he had had a normal cardiac catheterization six months earlier.

    His vital signs and physical exam were normal. An ECG was done (image), and the computer read it as a normal sinus rhythm at 74 bpm and ST-segment elevation with probable early repolarization.

    What is the most likely cause of the ECG findings in this patient? Acute coronary syndrome, pulmonary embolism, cardiac tamponade, or hypokalemia?

    Check the aVL

    My interpretation is that there is subtle ST elevation and hyperacute T-waves in leads I and aVL. These findings were especially concerning for occlusion MI given the relative ST elevation amount compared with the QRS voltage, which was small in these leads, and the reciprocal ST depression in III and aVF.

    Stephen W. Smith, MD, the author of Dr. Smith's ECG Blog (http://bit.ly/DrSmithsECGBlog), said the ST elevation in aVL looked to be minimal, but the QRS amplitude was tiny. ST elevation must always be assessed in proportion to the QRS size in that lead, and the ST/QRS ratio here was very high.

    He also noted that the most visually obvious finding was ST depression in III. This was of greater magnitude than the ST elevation in aVL, which could erroneously make one think that there was inferior subendocardial ischemia when actually it was reciprocal to occlusion myocardial infarction (high lateral occlusion MI).

    You should immediately check on the aVL to look for even subtle ST elevation or hyperacute T-waves whenever any ST depression is seen in the inferior leads. Here the T-wave in aVL was hyperacute. It was not tall, but it was bulky—wide with upward convexity (when normally it should have upward concavity). This was an occlusion, and the patient should have been taken to cath emergently.

    The correct answer in this case is acute coronary syndrome. The patient had emergency catheterization, which showed 95 percent stenosis of the proximal LAD. The initial troponin I was 0.76 ng/mL (99% URL <0.030: troponin I immunoassay, Abbott Laboratories). The troponin peaked at 12.8 ng/mL about 22 hours later. (Troponins usually peak about 24 hours after an acute event.)

    Case Lesson

    Subtle ECG findings with a concerning history and ongoing chest pain, even if quite mild, should be evaluated with an emergent cardiac cath. Do this even with recent reassuring stress test results or cardiac cath reports.

    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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