Cardiac Function Consequences of the Persistence of Acute Myocarditis Somatostatin-PET Criteria Four Months Post-Acute Phase

Background Somatostatin-Positron Emission Tomography (PET) imaging of inflammatory cells is an effective approach for detecting Acute Myocarditis (AM), based on the Myocardial Uptake Volume (MUV) criteria of > 18 cm 3 . The current study further characterizes patients for whom this criterion persists at the 4-month Follow-Up (FU) from apparently uncomplicated AM. Methods Twenty-seven patients [median age 26.5, inter-quartile range: 21.9-31.9 years], underwent Cardiac Magnetic Resonance (CMR) and [ 68 Ga]Ga-DOTA-TOC PET at the acute phase and 4.5 [4.2-5.0] months later. Patients with > 18 cm 3 MUV (FU.PET+) at the 4-month follow-up were compared to FU.PET-patients. Results At 4 months, inflammation by CMR was only identified in two patients but in 11 patients by PET (FU.PET+ group), with 5 of these 11 patients exhibiting a baseline-to-4-months expansion in MUV. Ejection Fractions (EFs) at 4 months were generally lower in FU.PET+ than FU.PET-patients (Left Ventricular (LV).EF, 52.9 [48.6; 55.0] % vs. 56.0 [54.3; 57.8] %, p=0.001). In addition, the 5 FU.PET+ patients with expansion of the MUV had a worse LV.EF evolution (4-month follow-up minus baseline difference in LV.EF: (−5.0) [(−12.9)-(−1.0)] %) vs. + 3.1 [0.94-8.0] % for the other patients, p=0.004) and the highest plasma high-sensitivity troponin-Ic at 4-months (13.0 [7.5-22.00] ng/l vs. 3.0 [2.0-9.5] ng/l, p=0.045) suggestive of a more persistent active disease. In contrast, the evolution profile of the 6-remaining FU.PET+ patients was consistent with a longer recovery time as a consequence of a more severe initial insult (i.e. with lower LV.EF and higher MUV at baseline vs. the other patients, both p < 0.05). Conclusions Myocardial inflammation is detected by somatostatin-PET at 4 months from an apparently uncomplicated AM in as many as 41% of patients. It is associated with a poorer recovery of cardiac function, consistent with more persistent active disease or a more severe initial insult. Clinical Perspective Although generally of mild severity, myocarditis may potentially involve dreaded complications such as heart failure, arrhythmia, and sudden cardiac death. We recently showed that the Somatostatin-positron emission tomography (PET) determination of inflammatory cell volume constitutes an alternative to cardiac magnetic resonance (CMR) imaging for detecting myocarditis at the acute phase. The present study shows that PET criteria of myocardial inflammation persist at four months from apparently uncomplicated myocarditis at a much higher rate than CMR (41% vs. 7% of patients). Moreover, this persistence is associated with a poorer recovery of cardiac function and is in line with two different evolution profiles—i.e., a more persistent active disease or a more severe initial insult. These new findings have the potential to improve monitoring and treatment adaptations for myocarditis patients. Graphical abstract