One T2-based marker of oedema plus one T1-based marker of injury (native T1, ECV or non-ischaemic LGE) makes the diagnosis; the LGE is typically subepicardial in the inferolateral wall and does not follow a coronary territory.
Orient first
- The 2018 Lake Louise criteria need BOTH a T2-based criterion (T2 mapping or T2-weighted STIR) AND a T1-based criterion (native T1, ECV or LGE) — one alone is supportive only.
- Myocarditis LGE is subepicardial or mid-wall, patchy, classically inferolateral — the opposite end of the wall from an infarct.
- Timing matters: oedema fades within weeks; scan within about 2 weeks of symptoms where possible.
Acquire the study
- Cine; T2 mapping (± T2-weighted STIR); native T1 mapping; LGE (PSIR) short axis and long axes; post-contrast T1 for ECV; pericardial assessment.
The manoeuvre
- T2 mapping: regional or global T2 above the local normal range (scanner- and sequence-specific) = oedema.
- Native T1 and ECV: raised in the same segments.
- LGE: subepicardial/mid-wall, patchy, inferolateral and basal lateral; spare the subendocardium; not in a single coronary territory.
- Cine: regional wall motion, LVEF; pericardial effusion and pericardial LGE (myopericarditis).
- Compare with coronary history: troponin rise with chest pain in an older patient needs MINOCA work-up, not a myocarditis label.
What confirms it
- A T2-based AND a T1-based Lake Louise criterion in a non-ischaemic distribution, in a compatible clinical setting.
What licenses you to exclude it
- Normal T2, T1/ECV and LGE make acute myocarditis unlikely, but an early or very late scan can miss mild disease — state the interval from symptoms.
The classic misread
- Calling subendocardial LGE myocarditis — that is an infarct pattern.
- Using a published T2/T1 cut-off from another scanner — normal ranges are site-specific.