Critical Care Medicine-Neurologic Disorders>>>>>Myocardial Disease
Question 4#

A 22-year-old male with no known medical history presents with insidious fatigue, nonproductive cough, and shortness of breath with exertion over the prior 3 weeks. His laboratory test results are notable for an elevated high sensitivity troponin to 60 ng/L, and an NT-proBNP elevated to 2,400 pg/mL. Ejection fraction on transthoracic echocardiogram is noted to be 15% but a normal LV dimension and wall thickness, with no other structural abnormality. He is admitted to the Cardiac ICU for further monitoring and management. You are suspicious for myocarditis. He exhibits no dysrhythmia on telemetry. His symptoms improve with medical management. 

The next best test to confirm a diagnosis is:

a. Viral serologies
b. Endomyocardial biopsy
c. Cardiac MRI
d. Cardiac PET scan

Correct Answer is C

Comment:

Correct Answer: C

Viral myocarditis is one of the most common causes of myocarditis. It may be caused by a variety of viral infections including hepatitis C, HIV, and enteroviruses among others, as well as bacterial and parasitic infections. Viral myocarditis may be preceded by upper respiratory tract symptoms, gastroenteritis, fatigue, fevers, and myalgias, followed by the onset of heart failure symptoms. Presentation can vary from occult heart failure to cardiovascular collapse or complex ventricular arrhythmias. With advances in imaging, cardiac MRI has been particularly useful in diagnosis of myocarditis. In myocarditis, cardiac MRI may show late gadolinium enhancement and relative myocardial enhancement compared to skeletal muscle, indicating damage, scaring, edema, and increased capillary permeability. 

Once MRI suggests myocarditis, endomyocardial biopsy is useful as it may exonerate other infiltrative etiologies including sarcoidosis, amyloidosis, and hemochromatosis. Biopsy is still considered the gold standard for diagnosis. However, the biopsy of the native heart is not without risks, such as ventricular perforation, valvular damage, and vascular injury. Thus, endomyocardial biopsy may be useful in select patients after cardiac MRI or when hemodynamic instability or need for rapid tissue diagnosis requires expeditious biopsy. Although cardiac PET scans can also assist in confirming the diagnosis of myocarditis, they are not easily available and needs preparation before testing and thus not the diagnostic modality of choice. Although viral serologies may be positive in a select number of patients, the overall sensitivity is poor, and thus these results are unlikely to change management. In this patient, with clinical improvement on medical management, cardiac MRI may be the next best test, to avoid risks of endomyocardial biopsy while assisting in assessment of a diagnosis, with biopsy considered only if there is no definitive diagnosis made by cardiac MRI and or concerning clinical trajectory.

References:

  1. Dennert R. Crijns HJ, Heymans S, et al. Acute viral myocarditis. Eur Heart J. 2008;29:2073-2082.
  2. Friedrich MG, Marcotte F. Cardiac magnetic resonance assessment of myocarditis. Circ Cardiovasc Imaging. 2013;6:833-839.