Discussion

Infective endocarditis remains an important complication in adults with CHD, with an incidence over 75 times higher than in the general population. ^{Reference Snygg-Martin, Giang, Dellborg, Robertson and Mandalenakis7} It is a leading cause of morbidity and mortality, with a reported mortality rate of 6.9 to 8%. ^{Reference Li and Somerville8,Reference Tutarel, Alonso-Gonzalez and Montanaro9,Reference Arvanitaki, Ibrahim and Shore10} A minority of species of coagulase-negative staphylococci, which are normal flora in humans, cause infection of prosthetic material and endocarditis.

SL is a new genomic species of gram-positive coagulase-negative staphylococcus identified in 1988, and it infects the skin and soft tissue predominantly. It can be differentiated from other coagulase negative species by its ability to produce ornithine decarboxylase and pyrrolidonyl arylamidase which allows it to bind fibrinogen with extracellular proteins causing agglutination. ^{Reference Anguera, Del Río and Miró5,Reference Liu, Huang and Tang6} Staphylococcus lugdunensis (SL) produce extracellular glycocalyx which helps with bacterial colonisation and interferes with neutrophil phagocytic activity. ^{Reference Liu, Huang and Tang6} It is said to account for ∼1.1% of all cases of infective endocarditis in one multicentre study causing ∼0.8% of native valve endocarditis. ^{Reference Anguera, Del Río and Miró5} In contrast to other coagulase-negative staphylococci which have an indolent course, Staphylococcus lugdunensis (SL) is an aggressive pathogen causing valve destruction, myocardial abscess formation, peripheral embolism and multiple complications similar to that seen with Staphylococcus aureus. It often affects native valves as opposed to coagulase-negative staphylococci, which affect prosthetic valves. ^{Reference Anguera, Del Río and Miró5,Reference Liu, Huang and Tang6}

Restrictive ventricular septal defects have been associated with a higher risk of infective endocarditis. High velocity turbulent left to right shunt from restrictive ventricular septal defect can affect the tricuspid valve leaflets or subvalvar apparatus and predispose to infective endocarditis. ^{Reference Alonso-Garcia, Fernandez-Hidalgo, Gonzalez-Fernandez, Roque, Pizzi and Pijuan-Domenech2} Therefore, both the 2015 American Heart Association and 2023 European Society of Cardiology guidelines categorise ventricular septal defect as a moderate risk factor for infective endocarditis. ^{Reference Alonso-Garcia, Fernandez-Hidalgo, Gonzalez-Fernandez, Roque, Pizzi and Pijuan-Domenech2} In the study by Anguera et al., only one patient had unrepaired congenital heart disease. ^{Reference Anguera, Del Río and Miró5} In a multicenter study of Staphylococcus lugdunensis (SL) endocarditis, CHD was a predisposing factor in 8.9% of patients with the precise nature of the CHD not elaborated. ^{Reference Lefevre, Habib and Hoen13}

While poor dentition and intravenous drug abuse are previously identified risk factors, immunocompromised individuals are a special population of patients at increased risk of infective endocarditis with increased mortality rates. ^{Reference Moore, Cao, Kotchetkova and Celermajer3,Reference Sidik, Chinikov and Korjueva11}

Our patient had two risk factors for infective endocarditis, including her underlying unrepaired CHD and being on immunosuppressive medication for autoimmune hepatitis. Despite the low-grade fevers, fatigue and malaise, she remained undiagnosed for a period until her acute onset of shortness of breath and pleuritic chest pain caused her to seek more emergent care. Timely assessment with chest Computed Tomography demonstrated an embolic phenomenon. Due to the chest Computed Tomography findings, she underwent echocardiography, which was crucial in diagnosing the infective endocarditis and the degree of tricuspid valve destruction.

The need for surgical intervention in infective endocarditis varies from 37 to 51% based on various studies. ^{Reference Arvanitaki, Ibrahim and Shore10,Reference Sidik, Chinikov and Korjueva11} Early surgery has been associated with shorter in-hospital stay compared to later surgery during the same hospitalisation or medical management. ^{Reference Sidik, Chinikov and Korjueva11} Both the American Heart Association and European Society of Cardiology recommend surgical intervention for right sided infective endocarditis in the presence of continued positive blood cultures for the causative microorganism despite 5 days of appropriate antibiotic therapy and recurrent emboli (septic pulmonary). The European Society of Cardiology additionally recommends surgical intervention for severe valvar dysfunction leading to recalcitrant heart failure and persistent tricuspid vegetation >20 mm. ^{Reference Wang and Fosbøl12} Persistent bacteraemia, the size of the vegetation and degree of tricuspid regurgitation, as well as the embolic phenomenon, were indications for surgery in our patient in accordance with published guidelines. A thorough and complete workup, along with earlier surgery, led to shorter hospital course and outpatient completion of antibiotic therapy in our patient.

A high index of suspicion should be maintained in patients with immunosuppression and unrepaired CHD for infective endocarditis in the presence of vague symptoms, which can sometimes be attributed to the underlying CHD. Patients with ventricular septal defect and immunosuppression can develop native valve endocarditis with atypical organisms usually infecting left-sided valves.