Clinical Pearls & Morning Reports

Posted by Carla Rothaus

Published October 19, 2022


When is endomyocardial biopsy indicated for the diagnosis of myocarditis?

Before the Covid-19 pandemic, the estimated global incidence of myocarditis was 1 to 10 cases per 100,000 persons per year. The highest risk was among people between 20 and 40 years of age and among men. Read the NEJM Review Article here.

Clinical Pearls

Q: Name some of the causes of myocarditis.

A: Myocarditis can result from a wide range of infectious or noninfectious causes, such as viruses, immune-system activation (autoimmunity [e.g., in sarcoidosis] or immune stimulation [e.g., vaccines or cancer therapies]), or exposure to toxins and drugs, including endogenous biochemical compounds, as seen in amyloidosis and in thyrotoxicosis. Among infectious forms of myocarditis, viruses are the most common cause.

Q: Is the use of immune checkpoint inhibitors associated with a risk of myocarditis?

A: Immune checkpoint inhibitor therapy represents a new approach to the treatment of advanced cancers in which antibodies targeting cytotoxic T-lymphocyte antigen 4, programmed cell death 1, or programmed death ligand 1 are used to enhance the T-cell–mediated immune response against tumor cells. However, systemic immune-mediated adverse events, including potentially life-threatening myocarditis, have been increasingly recognized, particularly with the use of combination immune checkpoint inhibitor therapy.

Morning Report Questions 

Q: When is endomyocardial biopsy indicated for the diagnosis of myocarditis?

A: Endomyocardial biopsy can be reserved for patients with clinically suspected myocarditis and the following findings: cardiogenic shock or acute heart failure requiring inotropic or mechanical circulatory support; ventricular arrhythmias or Mobitz type II second-degree or higher atrioventricular block, particularly when symptom onset is recent, with mild or no left ventricular dilatation; peripheral eosinophilia or an associated systemic inflammatory disorder; persistent or recurrent release of necrosis markers, particularly when an autoimmune condition is likely or ventricular arrhythmias and high-degree atrioventricular block are present; or cardiac dysfunction in a patient receiving immune checkpoint inhibitor therapy. In other clinical scenarios, cardiac MRI should be considered as the initial diagnostic test to detect inflammation, and endomyocardial biopsy may be considered on a case-by-case basis, according to the likelihood of detecting a treatable disorder.

Q: What are some of the factors of prognostic significance in patients with myocarditis?

A: The clinical presentation can be a predictor of the outcome. Patients with reduced left ventricular ejection fraction (LVEF), heart failure, advanced atrioventricular block, sustained ventricular arrhythmias, or cardiogenic shock are at increased risk for death or heart transplantation. An analysis of data from a collaborative registry of cases of acute myocarditis showed that most patients had an uncomplicated course, with chest pain in 97% of patients and ST-segment elevation on electrocardiography (ECG) in 62%, with no deaths or transplantations at 5 years. Heart transplantation or death from cardiac causes occurred almost exclusively in patients presenting with an LVEF of less than 50%, sustained ventricular arrhythmias, hemodynamic instability on admission, or a combination of these findings (rate of death or transplantation, 10.4% at 30 days and 14.7% at 5 years). Analysis of data from a multicenter registry of endomyocardial biopsy–confirmed acute myocarditis with systolic dysfunction (LVEF, <50%) showed the prognostic effect of hemodynamic compromise at presentation, with a 27.8.% rate of death or transplantation at 60 days among patients with cardiogenic shock, as compared with 1.8% among those without shock. The prognostic significance of the histologic characterization of inflammation was also confirmed, with giant-cell myocarditis carrying the highest risk.

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