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Incorrect ECG diagnoses?—Follow the Leads

To identify the key insights or developments described in this article
1 Credit CME

An individual in their early 70s presented to the emergency department with frequently recurring paroxysmal chest pain; each episode had a duration of 3 to 5 minutes. The patient had a medical history of hypertension and diabetes mellitus; vital signs were normal, except for elevated blood pressure (153/92 mm Hg). Chest auscultation revealed normal breath and heart sounds with no murmurs. The laboratory test results (hemogram, serum electrolytes, and troponin I and D-dimer levels) were all within normal limits. A chest radiograph showed no abnormality, and transthoracic echocardiography findings revealed normal left ventricular systolic function (ejection fraction, 60%). The electrocardiogram (ECG) tracing obtained on admission is shown in the Figure, A.

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When electrodes are placed in the wrong anatomic locations or clipped on the radial artery, they can produce incorrect ECG diagnoses. If the electrodes of leads V1 to V6 are placed on the right side of the chest, the amplitude of the QRS complex will gradually decrease from lead V1 to V6. When the left and right arm leads are placed inversely, the ECG manifests as follows1: (1) the P-QRS-T waves are inverted in lead I, ie, lead I is flipped (P wave is negative); (2) lead aVR resembles a normal aVL (P wave of aVR is positive), and lead II resembles a normal lead III; and (3) the precordial leads and aVF are unaffected. When the 2 aforementioned electrode misplacements occur simultaneously, the ECG characteristics will be the same as those of mirror-image dextrocardia.2 No mirror-image dextrocardia was found after performing a physical examination and chest radiography of the patient; therefore, these ECG changes denoted an instance of electrode misplacement.

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Article Information

Corresponding Author: Qingjie Xin, MD, Center for Coronary Artery Disease, Division of Cardiology, Beijing Anzhen Hospital, Capital Medical University, Anzhen Rd, Chaoyang District, Beijing 100029, China (qingjiexingood@126.com).

Published Online: March 6, 2023. doi:10.1001/jamainternmed.2022.6944

Conflict of Interest Disclosures: None reported.

References
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Chang  Q , Xu  Z , Liu  R .  Acute inferior wall myocardial infarction: what is the culprit artery?   Circulation. 2021;144(23):1893-1895. doi:10.1161/CIRCULATIONAHA.121.057659PubMedGoogle ScholarCrossref
2.
Reiffel  JA .  ECG response: can you make the correct morphology, pathology, and rhythm diagnoses?   Circulation. 2016;134(7):567-569. doi:10.1161/CIRCULATIONAHA.116.024356PubMedGoogle ScholarCrossref
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Zhai  HL , He  Y .  Transient ST-segment elevation and QTc interval prolongation in a patient with persistent chest pain.   JAMA Intern Med. 2021;181(12):1652-1653. doi:10.1001/jamainternmed.2021.6015PubMedGoogle ScholarCrossref
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Gregg  RE , Zhou  SH , Lindauer  JM , Helfenbein  ED , Giuliano  KK .  What is inside the electrocardiograph?   J Electrocardiol. 2008;41(1):8-14. doi:10.1016/j.jelectrocard.2007.08.059PubMedGoogle ScholarCrossref
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Li  C , Chang  Q , Yu  L , Liu  R .  An electrocardiographic artifact synchronized with the cardiac rhythm: a case report.   Ann Intern Med. 2022;175(3):456-458. doi:10.7326/L21-0660PubMedGoogle ScholarCrossref
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Aslanger  E .  Maybe a dazzle but not puzzle.   J Electrocardiol. 2010;43(6):682-684. doi:10.1016/j.jelectrocard.2010.04.010PubMedGoogle ScholarCrossref
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