Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
Myocarditis
Cardiology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
!
Escalate
Suspected myocarditis with shock, rapidly worsening heart failure, cardiac arrest, sustained ventricular arrhythmia, syncope, high-grade AV block or severe new ventricular dysfunction needs monitored admission and immediate discussion with a tertiary myocarditis and advanced-heart-failure service. Stabilisation, coronary exclusion and mechanical-support planning must not wait for a complete diagnostic work-up.
Synopsis
Recognise suspected myocardial inflammation, exclude coronary and other urgent mimics, select CMR or endomyocardial biopsy appropriately, stabilise haemodynamic and electrical complications, and plan cause-specific treatment, activity restriction and follow-up.
Myocarditis may look like acute coronary syndrome, decompensated heart failure, an arrhythmia or an unexplained conduction disorder; a recent viral illness is neither required nor diagnostic.
Use ECG, continuous rhythm observation when risk is significant, serial troponin, inflammatory markers, natriuretic peptide and transthoracic echo to establish injury and severity, not to assign a viral cause.
Do not label a troponin-positive chest-pain presentation as myocarditis until acute coronary occlusion has been assessed according to the patient's age, risk, ECG, instability and clinical probability.
CMR is the preferred non-invasive tissue test in a stable patient and should assess oedema, non-ischaemic injury, ventricular function, pericardial involvement and scar burden.
Endomyocardial biopsy is most useful when haemodynamic or electrical risk is high, the diagnosis remains uncertain, or histology and myocardial pathogen testing would change urgent treatment.
Shock, sustained VT or VF and advanced AV block require conventional resuscitation, pacing and advanced-heart-failure pathways alongside myocarditis investigation; consider temporary mechanical support early when shock is refractory.
Routine empirical immunosuppression or antiviral treatment is not appropriate for uncomplicated presumed viral myocarditis. Treat giant-cell, eosinophilic, sarcoid, immune-checkpoint-inhibitor and proven infectious disease through a subtype-specific specialist pathway.
Avoid vigorous exercise while inflammation or myocardial injury remains active. Return only after symptoms, biomarkers, ventricular function and clinically relevant rhythm risk have been reassessed.
Key red flags
Infarct-like presentation
Acute chest pain, ST-T change and troponin elevation may be indistinguishable from acute coronary syndrome at first contact. Pleuritic pain or a recent infection can support the history but cannot safely exclude coronary occlusion.
Heart-failure presentation
New exertional breathlessness, orthopnoea, oedema, raised JVP, gallop rhythm or ventricular dysfunction after an inflammatory illness suggests myocardial involvement. Hypotension, cool peripheries, oliguria, rising lactate or organ injury signals shock.
Electrical presentation
Palpitations, syncope, sustained ventricular tachycardia, ventricular fibrillation, frequent ventricular ectopy, new bundle-branch block or advanced AV block may be the dominant feature even when ventricular systolic function is preserved.
Immune-checkpoint-inhibitor signal
A patient receiving or recently exposed to immune-checkpoint inhibitor treatment who develops a troponin rise, weakness, arrhythmia, conduction disease or ventricular dysfunction needs urgent cardio-oncology assessment because deterioration can be rapid.
Investigation priorities
01
Immediate observations, ECG and rhythm monitoringFirst step
Identify ischaemia, ventricular arrhythmia, AV block and haemodynamic instability and establish whether a monitored setting is required.
Management branches
First contactRecognise risk and exclude coronary disease
Chest pain, troponin elevation, new ventricular dysfunction, arrhythmia or conduction disease with suspected myocardial inflammation.
Perform ABCDE assessment, 12-lead ECG, serial observations and troponin, targeted bloods and urgent TTE; use telemetry when syncope, conduction disease, ventricular arrhythmia or significant dysfunction is present.
Activate the acute coronary syndrome pathway when coronary occlusion remains plausible. Select invasive or CT coronary assessment from the patient's risk and stability rather than from the presence of a viral history.
Classify the patient as uncomplicated, heart-failure predominant, arrhythmic, or fulminant/shock presentation and arrange care in a setting able to respond to that risk.
Use CMR promptly in a stable patient once immediate coronary and other life-threatening alternatives have been addressed.
RecoveryProtect the ventricle and plan return to activity
The patient is haemodynamically stable and acute injury is resolving.
Treat persistent LV systolic dysfunction according to the dedicated NICE-aligned HFrEF chapter once haemodynamically stable; manage congestion, thromboembolism and clinically significant arrhythmia according to their own indications.
Key medicines
Disease-modifying HFrEF treatment after myocarditisThere is no myocarditis-specific class dose. Once shock has resolved and the patient is haemodynamically stable, select and titrate each indicated medicine using NICE NG106, the current product SmPC and the dedicated HFrEF chapter.Do not initiate or up-titrate long-term vasodilating or rate-limiting treatment during active shock. Check blood pressure, rhythm, volume state, renal function, potassium, contraindications and pregnancy status for each selected medicine.
Immunosuppression for defined immune-mediated myocarditisNo single empirical adult regimen is safe. The tertiary team should use the subtype-specific 2025 ESC protocol, pathology and infection assessment, patient weight and organ function to prescribe and document the exact regimen.Do not extrapolate to uncomplicated presumed viral myocarditis. Screen for relevant infection, coordinate specialty care and monitor glucose, blood pressure, FBC, renal and liver function, infection, gastrointestinal and bone risk, and treatment response.
Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Avoid vigorous exercise and competitive sport while symptoms, biomarkers, ventricular dysfunction, active imaging abnormalities or significant arrhythmia persist; give written safety-net advice for syncope, palpitations, chest pain or worsening breathlessness.
Reassess symptoms, examination, ECG, troponin when clinically indicated, ventricular function and rhythm burden. Use repeat CMR when it will document resolution or scar and change return-to-activity or risk decisions.
Make return to exercise individual and graded after clinical remission. Persistent ventricular dysfunction, complex ventricular arrhythmia or substantial residual scar requires specialist long-term follow-up rather than automatic discharge.