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Shark Sighting in an Electrocardiogram

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1 Credit CME

An individual in their late 50s was transferred from an outside hospital to our higher-level of care because of an elevated high-sensitivity cardiac troponin (hs-cTn) level and abnormal findings on an electrocardiogram (ECG). The patient had presented earlier that day to the outside hospital with nausea, vomiting, and an altered mental status. Medical history was remarkable for poorly controlled diabetes type 2 (treated with insulin) and polysubstance use (cocaine, cannabis, tobacco); there was no history of cardiac disease. The patient was reported to be hypotensive, tachycardic, and tachypneic. Results of multiple metabolic tests were abnormal (potassium, 5.9 mEq/L; HCO3, 3.8 mEq/L; glucose, 1472 mg/dL) and revealed acute kidney insufficiency (creatinine, 4.7 mg/dL; normal range, 0.4-1.3 mg/dL [to convert to μmol/L, multiply by 88.4]). The patient was treated for diabetic ketoacidosis and was intubated for airway protection. In addition, the patient’s total creatinine kinase level was 15 958 U/L (normal range, 11-204 U/L) and initial hs-cTn level was 284 ng/L (positive, >52 ng/L). The result of toxicologic screening was positive for cannabis. The presenting ECG showed sinus tachycardia with prominent T waves that were initially attributed to the patient’s metabolic derangement; however, several hours later, the hs-cTn level had risen markedly to 820 ng/L. The outside hospital repeated the ECG, and the results (Figure) prompted the transfer to higher-level care.

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The association of the shark fin pattern with STEMI, most notably, but also with stress cardiomyopathy and myocarditis, suggests that it may represent a more general response to myocardial injury. The exact mechanisms for this distinctive pattern are not known. However, several possibilities have been proposed, all likely resulting in a mismatch of endocardial or epicardial repolarization and creating a transmural voltage gradient, the characteristic large R wave, and downsloping ST segment—similar to the classic Brugada pattern also thought to be associated with such a gradient.7 There are 3 mechanisms that have been postulated: (1) ischemic, at the epicardial or microvascular level that may be enhanced by localized edema, as seen with stress cardiomyopathy or the inflammation associated with myocarditis8; (2) mechanical, related to localized abnormal wall motion and left ventricular cavity expansion, as seen with aneurysms9,10; and (3) catecholaminergic, owing to increased metabolic demand or microvascular constriction.9,10

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Article Information

Corresponding Author: Lynda E. Rosenfeld, MD, Section of Cardiovascular Medicine, Yale University School of Medicine, Dana 3, 789 Howard Ave, New Haven, CT 06510 (lynda.rosenfeld@yale.edu).

Published Online: December 12, 2022. doi:10.1001/jamainternmed.2022.5061

Conflict of Interest Disclosures: None reported.

References
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Kukla  P , Jastrzebski  M , Sacha  J , Bryniarski  L .  Lambda-like ST segment elevation in acute myocardial infarction - a new risk marker for ventricular fibrillation?: three case reports.   Kardiol Pol. 2008;66(8):873-877.PubMedGoogle Scholar
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Jaiswal  AK , Shah  S .  Shark fin electrocardiogram: a deadly electrocardiogram pattern in ST-elevation myocardial infarction (STEMI).   Cureus. 2021;13(6):e15989. doi:10.7759/cureus.15989PubMedGoogle ScholarCrossref
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Tarantino  N , Santoro  F , Guastafierro  F ,  et al.  “Lambda-wave” ST-elevation is associated with severe prognosis in stress (Takotsubo) cardiomyopathy.   Ann Noninvasive Electrocardiol. 2018;23(6):e12581. doi:10.1111/anec.12581 PubMedGoogle ScholarCrossref
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Bulut  M , Ekici  F , Ülgen Tekerek  N .  “Triangular QRS-ST-T waveform ECG pattern” during SARS-CoV-2 infection in a paediatric case with multiple comorbidities.   Cardiol Young. 2022:1-3. doi:10.1017/S1047951122001858 PubMedGoogle ScholarCrossref
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Lindner  G , Pfortmueller  CA , Braun  CT , Exadaktylos  AK .  Non-acute myocardial infarction-related causes of elevated high-sensitive troponin T in the emergency room: a cross-sectional analysis.   Intern Emerg Med. 2014;9(3):335-339. doi:10.1007/s11739-013-1030-y PubMedGoogle ScholarCrossref
7.
Kurita  T , Shimizu  W , Inagaki  M ,  et al.  The electrophysiologic mechanism of ST-segment elevation in Brugada syndrome.   J Am Coll Cardiol. 2002;40(2):330-334. doi:10.1016/S0735-1097(02)01964-2 PubMedGoogle ScholarCrossref
8.
Perazzolo Marra  M , Zorzi  A , Corbetti  F ,  et al.  Apicobasal gradient of left ventricular myocardial edema underlies transient T-wave inversion and QT interval prolongation (Wellens’ ECG pattern) in Tako-Tsubo cardiomyopathy.   Heart Rhythm. 2013;10(1):70-77. doi:10.1016/j.hrthm.2012.09.004 PubMedGoogle ScholarCrossref
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Brody  DA .  A theoretical analysis of intracavitary blood mass influence on the heart-lead relationship.   Circ Res. 1956;4(6):731-738. doi:10.1161/01.RES.4.6.731 PubMedGoogle ScholarCrossref
10.
Madias  JE .  Two possible mechanisms for the electrocardiogram diffuse ST-segment elevation in Takotsubo syndrome.   J Electrocardiol. 2013;46(4):346-347. doi:10.1016/j.jelectrocard.2013.01.010 PubMedGoogle ScholarCrossref
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