1357019 - Acute myocarditis in a second trimester pregnant woman; Noninvasive and contrast free tissue characterization.

23-year-old pregnant woman, who presented at 17 weeks of gestation with intense chest pain that radiate to her left arm, shortness of breath and malaise. Physical examination was unremarkable. On Initial work-up the EKG showed sinus rhythm with 75 bpm heart rate, right QRS axis deviation (+120°) and Bifascicular block (incomplete RBBB and LPFB), high-sensitivity troponin T in 1444 ng/L, NT-pro-BNP of 789 pg/ml and CRP of 10.4 mg/L, CBC showed Leukocytosis, COVID-19 testing was negative. Obstetric USG reported no concerning findings.

Diagnostic Techniques and Their Most Important Findings:

As part of institutional protocol, an echocardiogram was indicated, finding diffuse hypokinesia with preserved LVEF of 53%, normal RV function and no pericardial effusion.

Aiming to avoid the exposition to radiation and contrast agent, a non-contrast CMR was performed. Mildly reduced EF with normal volumes were reported: LFEV 46% and RVEF 42%. On black-blood T2-weighted inversion-recovery sequences, nonischemic subepicardial high signal intensities were found in the basal and mid inferolateral segments of the LV. On T1 and T2 mapping, increased inversion times were observed in the mentioned segments: mean time of 1250 ms for T1 and 65 ms for T2. No structural abnormalities were found. The study was concluded as positive for acute myocarditis and treated appropriately. Evolution was satisfactory, being discharged without complications.

Myocarditis results from an inflammatory response usually secondary to viral infection [1]. Since 2009, based on the Lake Louis criteria, CMR is the accepted noninvasive gold standard for the diagnosis of myocarditis [2]. The original criteria depend on the identification of myocardial edema, hyperemia and fibrosis/necrosis based on the analysis of T2-weighted signal intensities, early and late gadolinium enhancement. Diagnostic performance of the original criteria is high [4]. However, when myocardial damage is subtle or diffuse, the performance is affected. The development of T1 and T2 mapping sequences allows pixel wise tissue characterization based on specific relaxation times [4].

In 2018, Ferreira et al. published the updated Lake Louis criteria [3], which now incorporate the use of T1 and T2 mapping in addition to LGE as main criteria, improving the diagnostic performance with reported sensitivity of 87% and specificity of 96%[4]. In addition of improving the diagnostic reliability, native T1 and T2 mapping allow us to correctly diagnose myocarditis without the use of contrast agent, fact that is relevant in special population, such as is the case of our patient.

Learning Points from this Case:

The continuous evolution of cardiac magnetic resonance, allow us to diagnose life-threatening diseases such as myocarditis by non-invasive methods, avoiding the use of ionizing radiation and contrast agents, making it more suitable for specific conditions such as patients with severe renal disease, previous anaphylactoid reaction, pediatric patients and during pregnancy.