Myocarditis: Clinical sciences

Myocarditis refers to the inflammation of the myocardium, which can occur due to various reasons, including viral infections, medications, as well as systemic conditions, like sarcoidosis. Based on severity, myocarditis can range from asymptomatic and mild to life-threatening fulminant myocarditis, which is associated with heart failure!

Now, if your patient presents with chief concerns suggesting myocarditis, you should first perform an ABCDE assessment to determine if they are unstable or stable. If unstable, stabilize the airway, breathing, and circulation, which may require endotracheal intubation and mechanical ventilation. Next, obtain IV access and start continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry, as well as cardiac telemetry.

Myocardial inflammation can completely compromise myocardial function, so these patients could present with cardiogenic shock, requiring mechanical circulatory support and inotropes, like dobutamine! Finally, don’t forget to provide supplemental oxygen to maintain oxygen saturation above 90 percent.

Once you stabilize the patient, obtain a focused history and physical examination. Next, order labs, including CRP, ESR, and cardiac troponin, and don’t forget to obtain an ECG and transthoracic echocardiography or TTE. History typically reveals a young adult with no risk factors for ischemic heart disease, such as tobacco use, hyperlipidemia, and hypertension. Some patients might also report recent flu-like symptoms, including fever, malaise, and headaches. Finally, myocardial inflammation results in chest pain, palpitations, as well as dyspnea, and fatigue. Additionally, in unstable patients, there is impaired heart function, which eventually leads to congestive heart failure and symptoms, such as orthopnea and leg swelling.

Additionally, the physical exam will reveal signs of congestive heart failure, including jugular venous distention, S3 gallop, as well as lower extremity pitting edema. Next, elevated CRP and ESR confirm the presence of inflammation, while elevated cardiac troponin confirms the myocyte damage. Myocardial inflammation will also affect cardiac action potential and cause nonspecific ECG changes, including ST-segment elevation or depression, and T-wave inversion. Keep in mind that the involvement of pacemaker cells can result in conduction abnormalities, like AV block! Finally, the TTE will show increased myocardial wall thickness, reduced ejection fraction, and dilation of one or both ventricles. At this point, suspect fulminant myocarditis and order an endomyocardial biopsy, which is the gold standard to diagnose this condition, as well as cardiac magnetic resonance imaging.

Now, here’s another high-yield fact! Both ischemic heart disease and myocarditis can present with chest pain, elevated cardiac enzymes, and an abnormal echocardiogram. However, the treatment is different, so be sure to differentiate two conditions on time! Let’s begin with chest pain. The pain associated with ischemic heart disease is typically anginal, causing patients to feel a sensation of chest tightness and squeezing. Additionally, this pain gets worse with physical activity and alleviates with rest. On the flip side, in myocarditis, chest pain tends to be milder, more constant, and does not change with exertion. Moving on to the cardiac enzymes, in ischemic heart disease, you’ll find that they are markedly elevated while myocarditis tends to cause only mild elevations. Next, the echocardiogram in acute ischemia will show wall motion abnormalities, which are limited to the area specific to the affected coronary artery.

On the flip side, in myocarditis, the echocardiogram will show abnormalities involving the entire heart. Finally, you may consider cardiac catheterization to definitively rule out ischemic heart disease, especially in cases where symptoms overlap significantly.

Now, here’s a clinical pearl to keep in mind! Occasionally, myocarditis and pericarditis can occur simultaneously, a condition known as myopericarditis. In such cases, the physical exam will reveal a pericardial rub on heart auscultation, whereas the ECG shows diffuse ST-segment elevations and PR-segment depression. Additionally, the TTE might reveal the presence of a pericardial effusion.

Now, if the endomyocardial biopsy reveals myocardial inflammatory infiltration with or without myocyte necrosis, and cardiac magnetic resonance imaging shows myocardial edema, diagnose fulminant myocarditis!

Now, once you diagnose fulminant myocarditis, assess the biopsy findings! If the biopsy reveals lymphocyte infiltration, myocyte necrosis, and possible PCR identification of the viral pathogen, diagnose lymphocytic myocarditis, which typically occurs due to viral infections!