CMR Importance in Diagnosing Myocarditis Presenting as Inferolateral STEMI

Abstract

We present a case of a 20-year-old male patient who presented as an ST-segment elevation myocardial infarction picture with typical ECG and troponin rise, only to be found to have normal epicardial coronary arteries on coronary angiogram. However, a Cardiac Magnetic Resonance Imaging (CMR) was diagnostic of myocarditis.

Introduction

Myocarditis is a condition characterized by inflammation of the myocardium, typically manifesting suddenly. It is primarily attributed to viral infections like influenza and coronavirus, autoimmune disorders such as lupus, and certain medications like immune-checkpoint inhibitors [1]. The most prevalent symptom among patients is chest pain, although others may experience shortness of breath or sudden fainting episodes [2]. Electrocardiogram (ECG) findings in myocarditis cases are often diverse, lacking distinctive features for definitive diagnosis [3]. Nevertheless, as exemplified in our case, myocarditis can occasionally present with ECG alterations that strongly resemble those seen in acute myocardial infarction, featuring ST-segment elevation. This situation necessitates prompt evaluation through emergent coronary angiography to rule out any coronary artery involvement. Certain demographic and clinical features can be suggestive. After ruling out acute coronary syndromes, CMR imaging may confirm the diagnosis of myocarditis.

Case Presentation

A 20-year-old Brazilian male was admitted to the hospital due to chest pain. He had reported experiencing mild chest discomfort, aggravated when lying supine, along with headaches, fevers, and joint pains that did not respond to simple analgesia. The patient had no significant past medical history or family history of relevant diseases. He had no personal and family medical history of note, and he had received both doses of Coronavirus Disease 2019 (COVID-19) vaccination, with the last dose administered one year ago. He denied any recent gastrointestinal, respiratory, or flu-like symptoms, and had not traveled in the last three years since relocating to the United Kingdom.

Upon presentation, his ECG revealed inferolateral ST-segment elevation coupled with an increase in cardiac troponin (cTnT) levels (462ng/L) (Figure 1). However, the coronary angiogram exhibited unobstructed coronary arteries (Figure 2). Subsequent Cardiac Magnetic Resonance Imaging (CMR) performed two days later revealed signs consistent with localized myocarditis, including increased subepicardial signal in mid-lateral wall in T2 mapping (Figure 3A), subepicardial myocardial edema seen in mid-lateral wall in T2 black blood images (Figure 3B), and subepicardial LGE (Late Gadolinium Enhancement) seen in mid-lateral wall (Figure 3C).

Chest X-ray was unremarkable and a comprehensive myocarditis panel, as detailed below. The patient was admitted to the hospital for cardiac rhythm monitoring and was treated with colchicine and ibuprofen, with gradual improvement. He was then discharged on colchicine for a period of 3 months. On follow-up, the patient had no further symptoms and had completed his course of colchicine. A repeat Transthoracic Echocardiogram (TTE) showed normal function.

Discussion

Myocarditis is a challenging clinical entity to diagnose due to its diverse clinical presentations, which can mimic various cardiac conditions [4,5]. In this case, the patient presented with chest pain, cTnT elevation, and inferolateral ST-segment elevation on the ECG, a constellation of symptoms that can closely resemble a geographic ST-Elevation Myocardial Infarction (STEMI). However, it is crucial to emphasize that an angiogram remains an important step in the diagnostic workup to rule out unstable coronary artery disease before employing CMR to detect myocarditis. Myocarditis is known to occasionally present with variable ST segment changes [6].

Diagnosis can be suggested by a young age, absence of Coronary Artery Disease (CAD) risk factors, preceding viral symptoms, and diffuse ECG changes; however, as we demonstrated here, none of those features were diagnostic in our case, which required CMR to establish the diagnosis. Patients with myocarditis can exhibit clinical features such as chest pain, elevated troponin levels, and ECG changes that resemble those seen in STEMI.

This similarity in presentation can pose a diagnostic challenge, making it imperative to consider both conditions during the evaluation of such patients [7]. In this case, it was imperative to perform coronary angiography to exclude obstructive coronary artery disease. This step is crucial because timely intervention is critical in cases of acute coronary syndromes. Myocardial infarction due to coronary artery disease requires prompt revascularization, whereas myocarditis does not. Once angiography confirmed the absence of obstructive coronary lesions, CMR played a pivotal role in establishing the diagnosis of myopericarditis. CMR offers a non-invasive and highly sensitive method for assessing cardiac inflammation and detecting myocardial involvement [8]. In this case, CMR revealed evidence of acute myopericarditis with preserved biventricular systolic function, providing valuable insights into the underlying pathological process.

Conclusions

In summary, myocarditis can indeed masquerade as a STEMI, emphasizing the importance of a comprehensive diagnostic approach that includes coronary angiography to rule out coronary artery disease. Following the exclusion of obstructive coronary lesions, CMR becomes a valuable tool for confirming the diagnosis of myopericarditis. This case highlights the need for a meticulous and stepwise evaluation to differentiate between these two potentially life-threatening conditions and underscores the significance of using angiography before employing CMR in such cases.

Acknowledgements

Dr Ruta Virsinskaite, Cardiology CMR Registrar, Royal Free London Foundation Trust, London, UK. Dr Kotecha Tushar, Interventional Cardiologist, Royal Free London Foundation Trust, London, UK. Dr Sheref Zaghloul, Senior Cardiology Clinical Fellow, Royal Free London Foundation Trust, London, UK.

References