Cardiovascular

Myocarditis

Myocarditis is inflammation of the heart muscle that can present as an acute coronary syndrome mimic, new heart failure, ventricular arrhythmia or conduction disease; the immediate priorities are to assess instability, exclude time-critical alternatives, confirm myocardial inflammation and arrange cardiology follow-up.

In a nutshell

Myocarditis is myocardial inflammation that may present as chest pain with troponin release, new heart failure, ventricular arrhythmia or conduction disease. Treat acute coronary syndrome and shock as time-critical alternatives, use cardiac MRI as the key non-invasive test, monitor for electrical and haemodynamic deterioration, and arrange specialist follow-up before strenuous exercise. Specific immune-mediated forms need targeted specialist treatment.

Classic presentation

A young adult develops chest pain or breathlessness after a recent illness, with a troponin rise and ECG changes; the immediate task is to assess for acute coronary syndrome, ventricular dysfunction and arrhythmia before confirming myocarditis with multimodality imaging.

Key points

A troponin rise is myocardial injury, not a diagnosis: myocarditis and acute coronary syndrome can look similar.
Cardiac MRI using updated Lake Louise criteria is the key non-invasive test; endomyocardial biopsy is reserved for selected high-risk or treatment-changing cases.
Shock, acute pulmonary oedema, sustained ventricular arrhythmia, syncope or high-grade heart block requires urgent specialist escalation.
Treat persistent reduced ejection fraction using current NICE heart-failure guidance, but tailor treatment to haemodynamics, renal function, electrolytes and conduction.
Do not prescribe routine immunosuppression for presumed uncomplicated viral myocarditis; target treatment to a defined immune-mediated or specific inflammatory subtype.
Avoid strenuous or competitive exercise until clinical, biomarker, ventricular-function and rhythm recovery has been reviewed by the specialist team.
Follow-up should reassess symptoms, ECG, rhythm, ventricular function and residual inflammation or scar; recovery of symptoms alone is insufficient.

First-line investigation

ECG, serial troponin and clinical assessment with echocardiography; use coronary assessment when acute coronary syndrome is plausible and cardiac MRI to characterise myocardial inflammation.

Management

Stabilise and identify high-risk presentation

Treat shock, acute pulmonary oedema, malignant arrhythmia and severe conduction disease as emergencies; involve cardiology, critical care and an advanced heart-failure centre early when deterioration is present.^1,2

Exclude acute coronary syndrome and define cardiac injury

Use serial ECG, troponin and clinical assessment with echocardiography; follow the acute coronary syndrome pathway when indicated and do not let a presumed viral trigger delay reperfusion assessment.^3,1,2

Confirm inflammation and assess function

Use cardiac MRI with updated Lake Louise criteria as the principal non-invasive test; reserve endomyocardial biopsy for selected high-risk, deteriorating or treatment-changing cases.^1,2

Treat heart failure, arrhythmia and specific causes

Use specialist haemodynamic support for acute failure, current NICE heart-failure treatment for persistent reduced ejection fraction, urgent rhythm or pacing management when needed, and targeted therapy for defined immune-mediated or specific inflammatory disease.^4,5,2

Restrict exertion and document recovery

Avoid strenuous or competitive exercise until specialist review confirms acceptable symptoms, biomarkers, ventricular function, rhythm and inflammatory status; continue follow-up for residual scar, recurrent disease and arrhythmic risk.^1,2

Exam traps

A recent viral illness plus a raised troponin does not rule out acute coronary syndrome.
A normal initial echocardiogram or non-specific ECG does not exclude myocarditis.
Myopericarditis may cause diffuse ST elevation and pleuritic pain, but the myocardial troponin rise still requires assessment of ventricular function and coronary disease where indicated.
High-grade heart block or ventricular arrhythmia should prompt concern for fulminant or specific inflammatory disease, not reassurance from a modest troponin value.
Routine immunosuppression is not appropriate for presumed uncomplicated viral myocarditis; treatment depends on the cause and specialist assessment.
Return to sport is not based on symptom resolution alone: rhythm, biomarkers, ventricular function and ongoing inflammation must be reviewed.

Illustrations

Diffuse ST elevation in myopericarditisTwelve-lead ECG from a patient with myopericarditis showing widespread concave ST-segment elevation rather than a single coronary-territory pattern; the legend should warn that ECG pattern alone does not exclude acute coronary syndrome.James Heilman, MD, Wikimedia Commons · CC-BY-SA-4.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.