LVEF: left ventricular ejection fraction, RVFAC: right ventricular fractional area change
Follow ups: one patient underwent surgical removal of the thrombus which was mobile and adherent to the tendon of tricuspid valve anterior papillary muscle. Pathologically it showed patchy hemorrhagic necrosis without a normal tissue structure. The thrombus in all the remaining cases resolved with medical treatment in 22-89 days, median 53 days.
Discussion: Pediatric MP infection is usually mild and self-limiting. However, it may cause serious complications in some children in addition to the respiratory symptoms. There are growing reports of venous thrombosis or arterial embolism as the result of a MP infection[7-10]. MP infection can lead to hypercoagulable state, vascular endothelial damage, and even compromise the hepatic function affecting the synthesis of coagulation factors and thrombin. These multifactorial abnormalities can cause lower extremity venous thrombosis, pulmonary and cerebral embolism, etc. MP intracardiac thrombosis is rarely reported [6, 11]. Intracardiac thrombosis can be dangerous, as its detachment can cause major organ embolism or infarction, with serious consequences including disability and death [12-14]. Echocardiogram confirming or further suspecting an intracardiac thrombus will lead to further assessment and better treatment.
We found a case report of intraventricular thrombus associated with mycoplasma pneumonia [11]. The patient was a 9-year-old boy. On the 10th day of symptom onset, an MRI found a space occupying in the right ventricle which was surgically removed. Pathological findings were new fibrin thrombus with scarce white blood cells. The thrombus location, its illustrated and described characters, were similar to those of our current cases. In our 4 cases, intracardiac space occupying lesions were first revealed by echocardiography. The characteristic of the space occupying lesion together with the diagnosis of mycoplasma pneumonia and significantly elevated D-dimer lead to the diagnosis or high suspicion of a thrombus. Although incidence of mycoplasma pneumonia complicated with intracardiac thrombosis is very low, nevertheless, such a thrombus is dangerous for potential pulmonary embolism. Therefore, it is particularly important to have an echocardiogram examination in patients with mycoplasma pneumonia and significantly increased coagulation laboratory results. In our study, the thrombus occurred between 9-11 days after the onset of the fever. For those had higher D-dimer, we suggest an echocardiogram study 1-2 weeks after the onset of febrile illness to confirm or rule out a thrombosis. Except 1 case with thrombectomy, the thrombus in all the remaining cases is dissolved with medical treatment. Our cases suggest a good prognosis with early detection of the thrombus and prompt treatment. Otherwise, the large thrombus is a great risk for pulmonary embolism. In conclusion, MPP complicated with ventricular thrombosis is very rare. Therefore, when patients with MPP have abnormal coagulation lab results, imaging study should be done to rule out or confirm the thrombosis. Echocardiography plays an important role in the diagnosis with its location, size, number, shape, activity and its relationship with the surrounding tissues of the space occupying lesions. It also offers repeated follow ups.
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