The European Society of Cardiology (ESC) recently released its 2025 guidelines for the management of myocarditis, which also includes extensive discussion of pericarditis and the wide range of overlap between these types of cardiac inflammation. The guidelines were presented at the ESC Congress 2025 in Madrid and simultaneously published in the European Heart Journal.

Myocarditis is most likely underreported and underdiagnosed because of its nonspecific symptoms, including chest pain, dyspnea, fatigue, and fever and its potential for spontaneous recovery, said Leslie T. Cooper, Jr, MD, a US-based expert on the condition and past chair of cardiology at Mayo Clinic in Jacksonville, Florida. Acute myocarditis is typically seen in younger people, with a median onset between ages 30 years and 45 years and is more common in men than in women. While most cases resolve without complication, the condition carries a risk for sudden cardiac death that can strike even healthy, athletic individuals, Cooper told Medscape Medical News. According to data cited by the Myocarditis Foundation, up to 20% of sudden cardiac death cases in young adults are linked to myocarditis. Among young athletes, myocarditis has been called a “silent killer.”

New Take-Home Messages from ESC and US Guidelines

Recommendations in the new ESC guidelines are largely consistent with those of the 2024 American College of Cardiology (ACC) expert consensus decision pathway on managing myocarditis, and a 2025 joint ACC/American Heart Association scientific statement on return to participation for athletes with cardiovascular abnormalities.

“New in the current guidelines is the ability to make a definitive diagnosis without a biopsy, using cardiac magnetic resonance,” said Cooper, vice-chair of the writing committee for the ACC’s expert consensus statement on myocarditis. Cardiac imaging is superior for distinguishing between myocardial and pericardial inflammation and fibrotic tissue, the guidelines state. Data show late gadolinium enhancement on cardiac magnetic resonance is one of the strongest independent predictors of sudden cardiac death, all-cause mortality, and cardiac mortality.

“We recommend endomyocardial biopsy mainly for high-risk or treatment-refractory cases,” said Gianfranco Sinagra, MD, head of cardiothoracovascular medicine at the University of Trieste in Trieste, Italy, and a task force member for the ESC guidelines.

“Our guidelines also introduce a new diagnostic paradigm for classifying myocarditis as definite, possible, or unlikely/rejected. This shift may facilitate earlier diagnosis and risk stratification for routine clinical practice,” Sinagra told Medscape Medical News.

Also New This Year

Pericarditis in the Mix

The ESC guidelines coined “inflammatory myopericardial syndrome” (IMPS) as an umbrella term covering the overlap between myocarditis and pericarditis that can serve as a “temporary, initial diagnosis” and address mixed forms such as myopericarditis. “Managing IMPS necessitates a dual approach,” Sinagra said. “We need to address the pericardial inflammatory component while surveilling for complications suggesting myocardial injury, such as ventricular dysfunction or arrhythmias.”

Initial Treatment

Treatment of myocarditis/pericarditis is aimed at the underlying etiology — viral, toxic, parasitic, or autoimmune — and types of infiltrating cells. For a first episode of acute myopericarditis, European and US guidelines affirm the use of colchicine in combination with nonsteroidal anti-inflammatory drugs. In acute myocarditis, data show that omitting colchicine and failing to taper high-dose steroids are risk factors for recurrence or a chronic course of disease.

Return to Exercise

How soon a person with cardiac inflammation can resume physical activity has been a source of ongoing debate. Exercise and elevated heart rate can aggravate myocardial and pericardial inflammation and increase the risk for arrhythmia and sudden cardiac death in the acute phase.

However, prolonged inactivity also has implications for mental health and quality of life. “In my practice I often see young athletes who are paralyzed with fear when faced with a potentially life-threatening cardiac diagnosis,” Cooper said. “Our data have shown that nearly 44% of people with myocarditis have clinically significant symptoms of depression.”

While the decision should be individualized, current evidence supports a minimum rest period of 4 weeks, according to both US and European guidelines, after which patients with a mild course and low risk for complications can gradually return to activity. Monitoring should include assessment of symptoms, laboratory analysis for prognostic biomarkers, and imaging.

Classification Systems

A key difference between US and European guidelines is in how they classify myocarditis. European guideline staging is time-based:

• Acute: first 4 weeks

• Subacute: 1-3 months

• Chronic: lasting more than 3 months

Complicated cases are characterized by reduced left ventricular ejection fraction (< 50%), unstable arrhythmias, heart block, heart failure, or shock.

The ACC consensus statement offers similar definitions for acute and chronic myocarditis but adds a letter system to characterize severity:

Stage A: At risk based on exposure or genetic predisposition

Stage B: Subclinical: the presence of inflammation or injury without symptoms

Stage C: Active symptomatic myocarditis

Stage D: Advanced: fulminant or end-stage disease

Recognizing at-risk patient groups is important. This population includes an expanding number of patients receiving cardiotoxic drugs, such as immune checkpoint inhibitors and atypical antipsychotics like clozapine. Monitoring troponin levels in the second and third week of clozapine therapy is indicated to prevent this highly fatal form of myocarditis, Cooper said.

Many cases of myocarditis probably slip through the cracks, due to socioeconomic gaps in access to care and availability of advanced diagnostic technology, Cooper added. However, clear, updated guidelines for diagnosis and management can ideally help to prevent sudden cardiac death and long-term complications like heart failure.

Cooper reported receiving consulting fees from Moderna, Bristol Myers Squibb, Cardiol Therapeutics, and Foresee Pharmaceuticals and equity ownership in Stromal Therapeutics.

Sinagra reported no relevant financial conflicts of interest.

Katherine Wandersee has more than 30 years’ experience as a medical writer for professional medical audiences.