Treatment of the therapy-resistant right-sided endocarditis with low-dose systemic thrombolysis

Background
Right-sided endocarditis typically affects the tricuspid valve and is often managed conservatively with antibiotic treatment. However, in cases of uncontrolled infection despite appropriate antibiotic therapy, or with significant valve insufficiency, surgical intervention may be required. Some patients, however, are at high risk for surgery. We present a case of successful treatment of tricuspid valve endocarditis using low-dose systemic thrombolysis in an inoperable patient.

Case report
A 29-year-old female patient presented with a persistent fever lasting several weeks. She had a history of tricuspid valve endocarditis, treated by surgical resection of vegetation and tricuspid valve repair two years prior. Her medical history also included Crohn’s disease with colectomy and subsequent short bowel syndrome. She had a permanent Hickman catheter in the right subclavian vein for parenteral nutrition and pain medication. Additional diagnoses included fibromyalgia and rheumatoid arthritis.

Laboratory results showed leukocytosis, elevated CRP levels, and increased liver enzymes and renal function markers, leading to a diagnosis of sepsis. Blood cultures were collected, and she was started on piperacillin/sulbactam along with intravenous fluid administration. Echocardiography revealed a 2 x 5 cm vegetation on the tricuspid valve without significant insufficiency (Figure 1). Thoracic CT identified multiple pulmonary septic emboli. A diagnosis of tricuspid valve endocarditis with sepsis was confirmed, and all three blood cultures tested positive for methicillin-sensitive Staphylococcus aureus. Antibiotic therapy was changed to intravenous cefazolin combined with rifampicin and daptomycin, and the permanent venous catheter was removed. The patient stabilized and became afebrile; however, after four days of treatment, inflammatory markers rose again, and echocardiography showed an increase in the size of the tricuspid valve mass. The patient was referred to cardiac surgery for evaluation, but surgery was deemed too high-risk due to previous surgeries and her critical preoperative state.

Thus, low-dose thrombolysis was proposed to reduce the size of the vegetation and support antibiotic therapy. Continuous intravenous thrombolysis with rt-PA at a dose of 1 mg/hour was administered for 24 hours. Echocardiography showed a reduction in vegetation size, so the treatment was extended for an additional 24 hours without complications. After 48 hours, the vegetation was no longer detectable on the tricuspid valve (Figure 2). The patient’s clinical condition improved significantly, with no further fever, and inflammation markers decreased. Antibiotic therapy was continued for six weeks following admission, after which the patient was discharged.

Conclusion
Although antibiotic and surgical treatment options are effective for right-sided endocarditis, some patients, due to high surgical risk, are unsuitable for surgery and may have large intracardiac masses that do not respond to antibiotics alone. Typical endocarditis vegetation consists of an amorphous mass of platelets and fibrin in which microorganisms and inflammatory cells are enmeshed, making it potentially responsive to thrombolytic therapy. In this case, we successfully treated a patient with antibiotic-resistant, large, right-sided endocarditic vegetation using low-dose thrombolytic therapy. This enabled a reduction in vegetation size, allowing for effective antibiotic treatment.