Suspected myocarditis

2018 Lake Louise criteria

Cardiac MRI is the only test that can see myocardial inflammation directly, and it does so by measuring water and by showing where gadolinium lingers. Both signals decay with time from the acute episode, which makes when the scan happens as much a part of the decision as whether it happens.

Chest pain with a raised troponin and unobstructed coronary arteries, new unexplained heart failure or arrhythmia with a suspected inflammatory cause, or follow-up before return to competitive sport.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Accept as requested

Cardiac MRI — suspected myocarditis

Cardiac MRI

What we'd amend, and why

Inflamed myocardium holds extra water and has an expanded interstitium, and those two changes are detected by different physics. T2 is dominated by free water, so oedema prolongs it — that is the water-sensitive arm. Native T1 and extracellular volume rise with both oedema and fibrosis, and gadolinium, which cannot enter intact cells, accumulates and washes out slowly wherever the extracellular space is enlarged — that is the tissue-injury arm, seen as late enhancement in a subepicardial or mid-wall distribution rather than the subendocardial pattern of infarction. Requiring one criterion from each arm is what gives the diagnosis its specificity, and it is why omitting mapping to save table time changes the test into a less sensitive one.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwayadult — Adults
rulerule-mr-device-screening — MR safety screening for implants and foreign bodies; checked by Radiographer at the scanner
rulerule-contrast-reaction-premed — Prior contrast reaction and elective premedication; checked by Nurse before the scan
rulerule-gadolinium-renal — Kidney function and gadolinium-based contrast; checked by Radiographer at the scanner
rulerule-paeds-sedation — Sedation or anaesthesia for a child; checked by Nurse before the scan
rulerule-pregnancy-gadolinium — Gadolinium in known or possible pregnancy; checked by Radiographer at the scanner
rulerule-iv-access — Intravenous access adequate for the planned injection; checked by Radiographer at the scanner

Decision support only. Local protocol takes precedence.

Handled at the scanner(2)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

MR safety screening for implants and foreign bodies
Complete the MR safety questionnaire, verify implant labelling and its stated conditions of use against this scanner and this protocol, and ensure no ferromagnetic object enters Zone IV.
Radiographer at the scannerBefore the scan
Flags back if: An implant or retained foreign body that is MR Unsafe, unlabelled, or cannot be identified; or an MR Conditional device whose stated conditions this scanner or the requested protocol cannot satisfy; or a credible unexcluded intraocular metallic foreign body history.
Intravenous access adequate for the planned injection
Site and test a cannula that supports the protocol flow rate, preferring an antecubital or large forearm vein, and observe the injection for extravasation. A 20-gauge or larger cannula is preferred for flow rates of 3 mL/s or more.
Radiographer at the scannerAt the scanner
Flags back if: No cannula can be sited that supports the protocol flow rate — for example only a 22-gauge hand or foot cannula for a CT angiogram needing 4–5 mL/s; or the only available access is a central line or port that is not labelled power-injectable; or an extravasation occurs.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

Adults

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	Cardiac MRI Cardiac MRI — suspected myocarditis usually appropriate	Inflamed myocardium holds extra water and has an expanded interstitium, and those two changes are detected by different physics. T2 is dominated by free water, so oedema prolongs it — that is the water-sensitive arm. Native T1 and extracellular volume rise with both oedema and fibrosis, and gadolinium, which cannot enter intact cells, accumulates and washes out slowly wherever the extracellular space is enlarged — that is the tissue-injury arm, seen as late enhancement in a subepicardial or mid-wall distribution rather than the subendocardial pattern of infarction. Requiring one criterion from each arm is what gives the diagnosis its specificity, and it is why omitting mapping to save table time changes the test into a less sensitive one.
First line	Transthoracic echocardiography Transthoracic echocardiography — standard adult study usually appropriate	Echocardiography is the study that happens on the day of presentation and it answers the questions that decide the next few hours rather than the diagnosis: is there a pericardial effusion and is it compromising filling, is ventricular function impaired and by how much, is there a regional wall motion abnormality in a coronary territory that makes this an infarct, and is there a thrombus in a poorly contracting ventricle. Fulminant myocarditis declares itself here, as an acutely impaired and often thickened, oedematous-looking ventricle, and that finding changes the destination to a coronary care unit rather than an MRI list. It is complementary to and not competing with cardiac MRI: echo cannot see inflammation, and a completely normal echo does not exclude myocarditis — which is precisely why the MRI request survives it.
Second line	CT Coronary Angiogram (CCTA) CT Coronary Angiogram — ECG-Synchronised	Myocarditis is often a diagnosis of exclusion in a patient with chest pain and a raised troponin, and the exclusion that must be made first is obstructive coronary disease. Where invasive angiography has not been performed, CT angiography does this non-invasively and can be arranged quickly — and a normal study is what converts the presentation into the myocarditis pathway.

Pitfalls

Scheduling the scan weeks after the acute episode. Oedema resolves, the water-sensitive criterion turns negative, and a genuinely myocarditic patient is reported as showing only non-specific scar.
Accepting a protocol with late enhancement but no oedema-sensitive mapping — it reverts to an older, less sensitive diagnostic standard.
Applying mapping thresholds from a different scanner, field strength or vendor.
Mistaking subendocardial or transmural enhancement for myocarditis. That distribution follows a coronary territory and is infarction until proven otherwise.
Poor gating in an arrhythmic patient, which degrades exactly the sequences the diagnosis depends on — rate and rhythm should be checked before the appointment is issued.
Forgetting cardiac sarcoidosis, which uses the same toolkit, produces a similar pattern, and has an entirely different treatment.

Priors — what to pull first

Note the date of any previous cardiac MRI. Residual mid-wall enhancement months later is scar, not active inflammation, and the distinction is made by the mapping and oedema sequences rather than by the enhancement itself.
Where the question is fitness to return to sport, the comparator study is what makes resolution demonstrable.

What makes a good request

A good request gives the date of symptom onset, the troponin trend, whether coronary disease has already been excluded and how, the rhythm, and any device.
The diagnostic framework combines a water-sensitive criterion with a fibrosis- or expansion-sensitive one, so the protocol needs both oedema-sensitive imaging and late enhancement. A study with late enhancement alone under-calls acute inflammation.
Mapping values are specific to the field strength, the vendor and the sequence, and are meaningless without the local reference range — which is why a value quoted from another centre cannot be reused.

Scoring this once it is done

The classification and risk tools this question ends in.

eGFR (CKD-EPI 2021 Creatinine)

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

Cardiac MRI — suspected myocarditis Transthoracic echocardiography — standard adult study CT Coronary Angiogram — ECG-Synchronised

Confirm locally

Cardiac MRI — suspected myocarditis: timings are typical — confirm against local protocol.
Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.