Background: The detection of ongoing inflammation in
myocarditis patients has prognostic relevance and might be adequately evaluated
by cardiac MRI with its ability to noninvasively characterize myocardial
tissue. To date, there are only limited data on the detection of chronic
myocarditis and its differentiation from healed myocarditis based on a
cardiopathological reference standard.
Purpose: To assess the
performance of cardiac MRI for 1) the detection of chronic myocarditis
and 2) the discrimination of biopsy-proven chronic myocarditis from
healed myocarditis.
Materials and Methods: A
total of 80 consecutive participants with persistent (>30 days) symptoms
suggestive of myocarditis were prospectively enrolled from a single-center (university hospital) between January 2020 and August
2022. All participants underwent both endomyocardial biopsy for reference
standard diagnosis and a multiparametric 1.5 T cardiac
MRI protocol including mapping and late gadolinium enhancement (LGE). Mann‒Whitney U test, Fisher exact test and receiver
operating characteristic (ROC) curves were used for group comparison and evaluation of diagnostic
performance.
Results: Endomyocardial biopsy (performed
within a median of 1 day [IQR, 1-7] of cardiac MRI) revealed 40 of 80 participants (50%) with chronic lymphocytic myocarditis and 40 of 80 participants (50%) with healed myocarditis (median age, 48 years [IQR, 39-59]; 55
men, 25 women), median symptom
duration 3.5 months. At the time of
diagnostic workup, the most common symptom was dyspnea: 27 of 40 participants
(68%) with chronic myocarditis, and 18 of 40 participants (45%) with healed
myocarditis, P =0.07. Specifically, 9 of 40 participants (23%) with
chronic myocarditis suffered from dyspnea at rest (NYHA IV) vs. none of the
healed myocarditis group. Viral genomes and elevated
C-reactive protein as
inflammatory marker were exclusively detected in participants with chronic
myocarditis. Troponin was elevated in 14 of 40 participants (35%) in the
chronic group vs. in 3 of 40 participants (8%) in the healed group, P =0.005. NT-proBNP was elevated in 22
of 40 participants (55%) in the chronic group vs. in 6 of 40 participants (15%)
in the healed group, P <.001. LV-EF was lower in chronic myocarditis than in healed
myocarditis patients (38% vs. 50%), p=0.01. T2
mapping as a single parameter 1) showed
the best sensitivity in detecting chronic myocarditis (39 of 40, 98%; 95% CI:
87, 100) and 2) provided the best discrimination from healed myocarditis
as defined by the area under the ROC curve (AUC, 0.86; 95% CI: 0.77, 0.93; P
<.001), followed by LGE (AUC, 0.63), extracellular volume fraction (AUC,
0.62), and T1 mapping (AUC, 0.60).
Conclusion: A multiparametric
cardiac MRI protocol including T2 mapping allows detection of
ongoing myocardial inflammation and discrimination of chronic myocarditis from
healed myocarditis in participants with biopsy-proven myocarditis and symptoms
persisting for >30 days.