Clinical features of intracardiac thrombotic complication in patients with severe Mycoplasma pneumoniae pneumonia.

BACKGROUND

Intracardiac thrombus (ICT) is the rarest yet most severe complication of severe Mycoplasma pneumoniae pneumonia (SMPP) in children. This study aims to elucidate the clinical characteristics of patients with SMPP-related ICT.

METHODS

We retrospectively enrolled 68 children with SMPP (18 cases of ICT, 50 cases of non-ICT) who were admitted from January 2014 to January 2024. We compared their demographic data, clinical symptoms, laboratory tests, imaging findings, treatment strategies, and prognoses. Additionally, we summarized data from 33 confirmed SMPP-related ICT cases reported in 12 references.

RESULTS

In our cohort, the ICT group exhibited higher incidences of tachypnea, chest pain, inflammation, and elevated D-dimer levels. They also presented more severe radiological findings and had longer hospital stays compared to the non-ICT group. The chordae tendineae-attached was the most common type (61.1%). Pathological examinations revealed ICT sizes ranging from 480 to 31,500 mm³. A favorable prognosis was observed in 94.4% of ICT patients. Clinical features did not significantly differ between various ICT types. In the overall cohort (51 cases), the right ventricle was the predominant location (68.6%). Notably, 66.7% of patients had concurrent extracardiac thrombosis, with pulmonary thrombosis being the most common subtype (41.2%).

CONCLUSIONS

The clinical characteristics of SMPP-related ICT are non-specific, often coexisting with severe pulmonary lesions and significantly elevated inflammatory markers. All ICT types were chordae tendineae or wall-attached, rather than mobile. These findings suggest that an inflammation storm induced by SMPP may play a significant role in the pathogenesis of in situ thrombosis within the heart and major blood vessels.