Diagnostic performance of cardiovascular magnetic resonance native T1 and T2 mapping in pediatric patients with acute myocarditis

Abstract

Background: Multiple studies in adult patients suggest that tissue mapping performed by cardiovascular magnetic resonance (CMR) has excellent diagnostic accuracy in acute myocarditis, however, these techniques have not been studied in depth in children.

Methods: CMR data on 23 consecutive pediatric patients from 2014 to 2017 with a clinical diagnosis of acute myocarditis were retrospectively analyzed and compared to 39 healthy controls. The CMR protocol included native T1, T2, and extracellular volume fraction (ECV) in addition to standard Lake Louise Criteria (LLC) parameters on a 1.5 T scanner.

Results: Mean global values for novel mapping parameters were significantly elevated in patients with clinically suspected acute myocarditis compared to controls, with native T1 1098 ± 77 vs 990 ± 34 ms, T2 52.8 ± 4.6 ms vs 46.7 ± 2.6 ms, and ECV 29.8 ± 5.1% vs 23.3 ± 2.6% (all p-values < 0.001). Ideal cutoff values were generated using corresponding ROC curves and were for global T1 1015 ms (AUC 0.936, sensitivity 91%, specificity 86%), for global T2 48.5 ms (AUC 0.908, sensitivity 91%, specificity 74%); and for ECV 25.9% (AUC 0.918, sensitivity 86%, specificity 89%). While the diagnostic yield of the LLC was 57% (13/23) in our patient cohort, 70% (7/10) of patients missed by the LLC demonstrated abnormalities across all three global mapping parameters (native T1, T2, and ECV) and another 20% (2/10) of patients demonstrated at least one abnormal mapping value.

Conclusions: Similar to findings in adults, pediatric patients with acute myocarditis demonstrate abnormal CMR tissue mapping values compared to controls. Furthermore, we found CMR parametric mapping techniques measurably increased CMR diagnostic yield when compared with conventional LLC alone, providing additional sensitivity and specificity compared to historical references. Routine integration of these techniques into imaging protocols may aid diagnosis in children.

Keywords: Cardiovascular magnetic resonance; Extracellular volume; Myocarditis; Pediatrics; T1 mapping; T2 mapping.

Fig. 1

ROC Curves for CMR Mapping Parameters to Identify Patients with Acute Myocarditis. Receiver-operating curves (ROC) illustrate the performance of (a) global native T1, (b) global T2, and (c) extracelluar volume fraction (ECV). Ideal cut-off values for each mapping parameter were generated from each respective curve, (d) global native T1 mapping and global T2 mapping, and (e) global T1 mapping and maximum segmental T2 mapping (maxT2)

Fig. 2

Cardiovascular Magnetic Resonance (CMR) Flowchart of Patients with a Clinical Diagnosis of Myocarditis. Applying generated cut-off values of each of the parametric mapping values (global native T1, global T2, and ECV) identified 90% of patients missed by the traditional Lake Louise Criteria (LLC). Only a single patient did not demonstrate positive findings by the LLC or by any of the mapping parameters

Fig. 3

Selected cardiovascular magnetic resonance (CMR) images from a 1.5 year old girl with a clinical diagnosis of acute myocarditis. The top panel demonstrates normal selected images from the Lake Louise criteria (LLC), with: (a) no increased T2-weighted (T2W) signal intensity, (b) no evidence of late gadolinium enhancement (LGE), (c) no increased early gadolinium enhancement (EGE) and a pericardial effusion. The bottom panel demonstrates abnormal (d) T2M and (e) ECV maps in the mid-portion of the short-axis. The global native T1 was 1270 ms, the global T2 was 60 ms and ECV was 39.6%