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STEMI in a patient with mirror-image dextrocardia

Harris, K. Yvonne DSc, EMPA-C; Umar, Mohamad DSc, EMPA-C

Journal of the American Academy of PAs: October 2019 - Volume 32 - Issue 10 - p 25–28
doi: 10.1097/01.JAA.0000579180.30494.4d
Case Report
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ABSTRACT ST-segment elevation myocardial infarction (STEMI) is a potentially life-threatening diagnosis that cannot be missed on ECG interpretation. However, ECG interpretation may not be straightforward in patients with dextrocardia. This case report discusses the presentation of a patient with situs inversus with dextrocardia who was found to have an acute inferior MI, and how this anatomical change results in an atypical ECG and clinical presentation.

K. Yvonne Harris is a graduate of the US Army-Baylor University doctor of science emergency medicine PA residency program and practices emergency medicine at the Eglin Air Force Base hospital in Florida. Mohamad Umar is on the faculty of the US Army-Baylor University emergency medicine PA residency program and practices emergency medicine at San Antonio Military Medical Center. The views expressed in this article are those of the authors and do not reflect the official policy or position of Brooke Army Medical Center, the US Army Medical Department, the US Army Office of the Surgeon General, the Department of the Army, the Department of the Air Force, the Department of Defense, or the US government. The authors have disclosed no potential conflicts of interest, financial or otherwise.

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CASE

Figure

Figure

A 60-year-old woman presented to the ED with persistent right-sided pressure-like chest pain radiating to both shoulders that started the day prior. She described the pain as being similar to a myocardial infarction (MI) she had 8 years ago.

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History

The patient initially presented to a community urgent care center after the onset of pain and was told she was “trying to have a heart attack,” prompting a transfer to a community ED. She said she left this facility against medical advice because of the long wait for admission. At home, she applied a nitroglycerin patch for pain relief before going to bed and upon awakening the following morning with continued chest pain decided to report to the ED. Her past medical history included mirror-image dextrocardia associated with situs inversus totalis, previous MI, and coronary artery disease that was treated with four stent placements, hypertension, hyperlipidemia, type 2 diabetes requiring insulin, and obesity. She takes aspirin, clopidogrel, metoprolol, lisinopril, atorvastatin, nitroglycerin patch, metformin, insulin aspart, and glargine. She denied tobacco, alcohol, and illicit drug use.

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Physical examination

On arrival to our ED, the patient's vital signs were BP, 154/89 mm Hg; heart rate, 53 beats/minute; respirations, 20; SpO2, 99% on room air; and temperature, 98.3° F (36.8° C). She appeared to be uncomfortable in the hospital gurney but otherwise in no apparent distress. Her heart sounds were auscultated over the right anterior chest and revealed an S1 and S2 with regular rate and rhythm. No S3, S4, murmurs, gallops, or rubs were appreciated. Her lungs were clear to auscultation in all lung fields without adventitious lung sounds such as wheezing, or crackles. Her abdomen was soft, nontender, nondistended, with normoactive bowel sounds, and without palpable mass. No lower extremity edema or jugular venous distension was noted on examination to suggest fluid overload. Distal pulses were palpated in all extremities 2+ and equal throughout.

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Diagnostic studies

A traditional left-sided ECG was initially performed by triage because of the patient's active chest pain (Figure 1). This was followed by a right-sided ECG given the patient's dextrocardia (Figure 2), which revealed sinus bradycardia at a rate of 52 beats/minute with a large negative QRS complex and inverted P wave in leads I and aVL; positive QRS complex and upright P wave in lead aVR; ST-segment elevation in leads I, II, and aVF; T-wave inversion in leads V1 and V2; and ST-segment depression in lead aVR and V2. A portable one-view chest radiograph displayed situs inversus and right perihilar airspace opacities concerning for pulmonary edema (Figure 3). Cardiac biomarker troponin T was elevated at 0.584 ng/mL (normal range, less than 0.1 ng/mL). The remaining laboratory studies were noncontributory.

Box 1

Box 1

FIGURE 1

FIGURE 1

FIGURE 2

FIGURE 2

FIGURE 3

FIGURE 3

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Treatment

The patient was diagnosed with an ST-segment elevation myocardial infarction (STEMI) and the cardiac catheterization laboratory and team were activated. She was placed on a cardiac monitor and provided supplemental oxygen by nasal cannula with a goal to maintain oxygen saturation above 92%. The patient had self-administered aspirin 325 mg by mouth before ED arrival, so this medication was held. Given concerns about cardiac preload dependence, she was cautiously given sublingual nitroglycerin 0.4 mg three times with some pain relief and started on maintenance IV 0.9% sodium chloride solution while her BP was monitored. She was given oral clopidogrel bisulfate 600 mg and IV heparin 4,000 units as a bolus.

The patient was then transported to the cardiac catheterization laboratory, where emergent coronary angiography revealed a 90% thrombotic stenosis of the mid-right coronary artery (RCA) and 80% stenosis of the proximal left anterior descending (LAD) artery. Percutaneous coronary intervention (PCI) was performed with placement of two drug-eluting stents in the mid-RCA and one drug-eluting stent in the proximal LAD.

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Outcome

Postprocedurally, the patient was admitted to the coronary care unit. Her chest pain completely resolved. A repeat right-sided ECG following the PCI revealed resolution of the ST-segment elevation in leads I, II, and aVF; resolution of the T-wave inversion in leads V1 and V2; and resolution of the ST-segment depression in lead V2 (Figure 4). A technically difficult transthoracic echocardiogram was performed after the PCI and exhibited a wall motion abnormality of the proximal LAD territory with an estimated ejection fraction of 45% to 50%. Her medical management was optimized by dual antiplatelet therapy with aspirin and clopidogrel bisulfate, a beta-blocker, high-intensity statin therapy, and an angiotensin-converting enzyme inhibitor. From a cardiac standpoint, she recovered without chest pain recurrence or cardiac complications such as dysrhythmias. She was discharged with plans to complete cardiac rehabilitation.

FIGURE 4

FIGURE 4

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DISCUSSION

STEMI is a potentially life-threatening diagnosis that cannot be missed on ECG interpretation. However, evaluation for ST-segment elevation can be challenging in patients with mirror-image dextrocardia. Despite advances in imaging technology, patients with mirror-image dextrocardia may not be aware of their condition. This uncommon congenital heart anomaly occurs in about 1 in 10,000 people and may be associated with other medical comorbidities such as chronic sinusitis and bronchiectasis in Kartagener syndrome.1 Although mirror-image dextrocardia is an infrequent finding, it is the most common cardiac positioning abnormality and is primarily associated with situs inversus, in which all major visceral organs have a mirror-image orientation.2 In mirror-image dextrocardia, the heart develops in the right thoracic cavity with the apex pointing toward the right hemidiaphragm with a reversal of the traditional right-left orientation. Dextrocardia differs from dextroposition, where extracardiac factors displace the heart into the right hemithorax, and dextroversion, which has a rotational component to the cardiac anomaly. Embryologically, situs inversus with dextrocardia develops in the fetal heart when the primitive cardiac tube loops in a leftward fashion instead of rightward as seen in situs solitus (normal cardiac position).3,4 The cause of dextrocardia with situs inversus is largely unknown; however, patients with dextrocardia do not appear to be at an increased risk for intracardiac abnormality or coronary atherosclerotic disease despite the abnormal cardiac positioning.2,5,6 In dextrocardia, the left and right orientation of the heart is inverted; however, the anterior-posterior relationship of the heart is unchanged.

This abnormal cardiac positioning can result in atypical clinical presentations, which may delay the diagnosis of emergency conditions and points to the importance of obtaining a thorough medical history and maintaining a healthy level of clinical suspicion.

The clinical approach to evaluating patients with dextrocardia should include awareness that the patient's inverted anatomy will affect symptom location and physical examination findings. Because the heart is located in the right thoracic cavity, chest pain is likely to originate on the right. The pain radiation pattern is variable and has been described as radiating to both upper extremities and the jaw similar to typical angina.7 Right-sided chest pain may be attributed to pleural, musculoskeletal, neurologic, or gastrointestinal pathology instead of angina.

An ECG to evaluate right-sided chest pain in a patient with dextrocardia may be challenging to perform and interpret. For example, standard lead placement will result in a right axis deviation, polarity reversal in leads I and aVL, positive P-wave and QRS complex in aVR, and reversed R-wave progression. Appropriate lead placement in patients with dextrocardia is unclear. Multiple case reports recommend performing a right-sided ECG by reversing all precordial and limb leads to normalize the ECG.6-8 The Society for Cardiological Science and Technology, however, recommends performing a standard left-sided ECG followed by a modified right-sided ECG in which the limb leads and precordial leads V1 and V2 remain unchanged and only the precordial leads V3 through V6 are reversed.9 Mitchell and colleagues suggest that maintaining limb lead inversion in the modified right-sided ECG reminds the interpreter of the abnormal cardiac positioning.8 Despite these opposing thoughts, proper documentation of lead placement on the ECG is essential for patients with dextrocardia, to prevent potential errors in ECG interpretation. Clinicians may confuse ECG findings consistent with dextrocardia with limb lead placement errors in which the main difference is the precordial R-wave progression. In limb lead reversal, the precordial leads should have a typical R-wave progression; in patients with dextrocardia, the progression is reversed. Precordial lead reversal is critical in dextrocardia as this may expose hidden ST-segment elevation in the anterior, septal, and lateral leads. A case report by Richter and colleagues describes a patient with an acute anterior MI that was only identified after precordial lead reversal on ECG.10 He and colleagues described a patient with an acute lateral MI that was not apparent on a standard left-sided ECG and seen only on a right-sided ECG.7 Inferior STEMIs should be identifiable on standard left-sided ECGs because leads II, III, and aVF are unaffected in dextrocardia.

Clinical acumen about dextrocardia may prompt clinicians to place automated external defibrillator (AED) pads in a mirrored fashion similar to ECG leads; however, no studies have evaluated appropriate placement of AED pads in patients with dextrocardia. In fact, Cattermole and colleagues described a successful defibrillation with traditional anterolateral paddle positioning in a patient with unknown dextrocardia who was in ventricular fibrillation arrest.11 Gorenek and colleagues also described a successful cardioversion in a patient with dextrocardia by placing the paddles on the conventional right parasternum and atypical right lateral chest at the heart apex.12 These case reports suggest that AED pad placement may be less important than the energy that they deliver, though further studies are needed to further evaluate this. Fortunately, STEMI management in patients with dextrocardia is the same as in patients with normal heart position, although coronary angiography and percutaneous coronary intervention may be more technically challenging due to mirrored anatomy.

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CONCLUSION

This case presents a common chief complaint in a patient with an unusual medical condition. Dextrocardia is rarely seen in the ED but clinicians must understand it. Recognizing the atypical clinical presentation, unusual ECG findings, and necessity of a right-sided ECG in patients with dextrocardia complaining of chest pain can prevent delayed or missed STEMI diagnoses.

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REFERENCES

1. Sharma S. Situs inversus totalis (dextroversion)–an anatomical study. Anatomy Physiol. 2012;2(5):1–3.
2. al-Khadra AS. Images in cardiovascular medicine. Mirror-image dextrocardia with situs inversus. Circulation. 1995;91(5):1602–1603.
3. Maldjian PD, Saric M. Approach to dextrocardia in adults: review. AJR Am J Roentgenol. 2007;188(6 suppl):S39–S49.
4. Jauhar R, Gianos E, Baqai K, et al Primary angioplasty in a patient with dextrocardia. J Interv Cardiol. 2005;18(2):127–130.
5. Genetic and Rare Diseases Information Center. Dextrocardia with situs inversus. https://rarediseases.info.nih.gov/diseases/6268/dextrocardia-with-situs-inversus. Accessed April 25, 2019.
6. Tanawuttiwat T, Vasaiwala S, Dia M. ECG image of the month. Mirror mirror. Am J Med. 2010;123(1):34–36.
7. He J, Sun Y, Zhang X, et al Emergent percutaneous coronary intervention for acute myocardial infarction in patients with mirror dextrocardia: case reports and brief review. Cardiovasc Diagn Ther. 2016;6(3):267–273.
8. Mitchell C, Perkins Z. Prehospital thrombolysis of acute myocardial infarction in dextrocardia. Emerg Med J. 2007;24(10):730–731.
9. Campbell B, Richley D, Ross C, Eggett CJ. Clinical guidelines by consensus: recording a standard 12-lead electrocardiogram. An approved method by the Society for Cardiological Science and Technology (SCST) 2017. http://www.scst.org.uk/resources/SCST_ECG_Recording_Guidelines_20171.pdf. Accessed May 14, 2019.
10. Richter S, Döring M, Desch S, Hindricks G. ECG pitfall: anterior myocardial infarction in dextrocardia. Eur Heart J. 2014;35(28):1887.
11. Cattermole G, McKay N. A case of dextrocardiac ventricular fibrillation arrest. Emerg Med J. 2006;23(2):147–148.
12. Gorenek B, Kuskus S, Kudaiberdieva G, et al Electrical cardioversion of atrial fibrillation in a case of dextrocardia. Can J Cardiol. 2004;20(8):819–821.
Keywords:

situs inversus; dextrocardia; myocardial infarction; STEMI; ECG; chest pain

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