Myocarditis and Sport

The history is often the clue: cardiac symptoms appearing days to weeks after a viral illness. Chest pain is common and may feel like pericarditis or mimic a heart attack, and there may be breathlessness, palpitations, light-headedness or, in athletes, a fall in performance and exertional fatigue that does not settle as the virus clears. The spectrum is broad, from mild or barely noticeable illness to acute heart failure, serious arrhythmia and, at its most severe, cardiac arrest.

Because the early picture can be subtle, new cardiac symptoms or unexplained underperformance after an infection should be taken seriously rather than attributed to lingering viral fatigue. The differential is wide, including pericarditis, an acute coronary syndrome, a pulmonary embolism, a chest infection, exercise-induced breathing problems and post-viral fatigue, so the skill is less about diagnosing myocarditis at the bedside and more about recognising when to stop exercise and escalate. Examination may be normal or may show a fast or irregular pulse, signs of heart failure, or a pericardial rub.

First-line assessment usually includes a twelve-lead electrocardiogram, troponin, inflammatory markers and a full blood count, with echocardiography when cardiac involvement is suspected or symptoms are significant. The electrocardiogram (ECG) is usually abnormal but the changes are non-specific, and a normal tracing does not rule the diagnosis out. Blood troponin, a marker of heart muscle injury, is frequently raised, though a single normal result does not clear an athlete with convincing symptoms, and repeat testing or monitoring may be needed.

Echocardiography assesses the heart's pumping function and wall movement and helps exclude other causes. The key non-invasive test is cardiac magnetic resonance imaging (cardiac MRI), which characterises the muscle tissue using the Lake Louise criteria, showing oedema on water-sensitive imaging and injury on other sequences, and has largely replaced the need to sample heart muscle.

Sampling the muscle directly, an endomyocardial biopsy, is reserved by specialists for selected high-risk cases, such as a fulminant course, severe unexplained ventricular impairment or dangerous arrhythmia. Throughout the work-up, the athlete should not be exercising.

Care is led by cardiology, and the SEM clinician's contribution is recognition, sensible first advice and supporting a safe return. Treatment is largely supportive, alongside managing the specific cause and treating any heart failure or arrhythmia, with more intensive care for the few who present severely. The cornerstone for an athlete is rest.

Traditional sports cardiology guidance restricts competitive sport and intensive training for about three to six months from onset, with the shorter end more typical of mild, fully recovered cases and the longer end where there is impaired function or residual scar. Newer guidance is more individualised, but the principle holds: return follows recovery and objective reassessment, and is set by the specialist.

Return is never automatic. Before going back to intensive training or competition, an athlete should be symptom-free, with recovered heart function on imaging, normal or clearly settling troponin and inflammatory markers, and no significant arrhythmia on monitoring and usually exercise testing. Repeat cardiac magnetic resonance imaging is most useful where the first scan showed oedema, scar or impaired function, where symptoms persist, or before a return to higher-intensity sport, rather than being mandatory for every low-risk athlete.

Persistent dysfunction, ongoing inflammation or extensive scar should delay return and prompt specialist review, and new palpitations or exertional blackout during recovery should trigger reassessment rather than self-clearance. The pandemic shaped a practical pathway: athletes with cardiac symptoms or a more severe illness after COVID-19 warrant assessment before returning, while those with mild or no symptoms can usually return through a graded programme without extensive testing.

The enduring principle is the simplest one, that an athlete should not train or compete with a fever, systemic viral symptoms, chest pain, unusual breathlessness or palpitations, and that new cardiac symptoms after a virus are a reason to stop and assess.

• •European Society of Cardiology guidance on myocarditis and pericarditis, including the inflammatory myopericardial syndrome framework, and European sports cardiology guidance inform diagnosis, exercise restriction and return-to-sport assessment.
• •Cardiovascular magnetic resonance criteria, known as the Lake Louise criteria, support the non-invasive diagnosis of myocardial inflammation.
• •Consensus return-to-play guidance developed after COVID-19 informs the assessment of athletes with cardiac symptoms following infection.
• •National Institute for Health and Care Excellence (NICE) guidance on recent-onset chest pain supports emergency referral, electrocardiogram and troponin assessment, and reminds clinicians that a raised troponin can reflect causes such as myocarditis.
• •Patient organisations including the British Heart Foundation and Cardiac Risk in the Young (CRY) provide information and support.

• •Myocarditis is inflammation of the heart muscle, usually viral, and is a recognised cause of sudden cardiac death in young athletes.
• •It often follows a viral illness, with chest pain, breathlessness, palpitations or exertional symptoms, and ranges from mild to fulminant heart failure.
• •Troponin is often raised and the electrocardiogram often abnormal but non-specific; cardiac magnetic resonance imaging, using the Lake Louise criteria, is the key non-invasive test.
• •The acute phase demands rest, because exercise can worsen the injury and trigger fatal arrhythmias.
• •Return to sport is graded and specialist-led, after symptoms resolve, function recovers and markers normalise, with no significant arrhythmia, over a period of about three to six months tied to severity.
• •After COVID-19, athletes with cardiac symptoms warrant assessment before return, while mild or asymptomatic cases can usually return through a graded programme.