We present the case of an 80-year-old patient with endocarditis on a biological prosthetic valve, of uncertain aetiology, which caused an abscess on the valve with dehiscence of the annulus. The patient had no known allergies. He had been an ex-smoker of 20 cigarettes/day for more than 20 years, and consumed 2 glasses of wine per day. Independent for basic activities of daily living. Two years ago he went to the emergency department of his reference hospital for progressive dyspnoea to the point of minimal effort. At that time, the patient had a personal history of glaucoma, hyperuricaemia, DM II and hypercholesterolaemia. Transthoracic echocardiography (TTE) performed during admission revealed a silent myocardial infarction in the inferolateral wall (akinesia with thinning of the wall), moderate mitral insufficiency, dilated left ventricle (LV) (end-diastolic volume 155 ml) and hypertrophic (interventricular septum in diastole 13 mm) with a left ventricular ejection fraction (LVEF) of 60% by the Simpson biplanar method. He was discharged with a diagnosis of emphysema-type COPD with bilateral subpleural pulmonary bullae (FEV1/FVC 40.94% post-BD) and established infarction of uncertain chronology inferolaterally.

At the one-year follow-up TTE, severe eccentric mitral regurgitation was detected with a drop in ejection fraction and worsening dyspnoea: LVEF 47% by Simpson biplanar. The patient was proposed for cardiac surgery. Preoperative coronary angiography showed significant 2-vessel coronary artery disease (severe stenosis in the LAD and proximal DC), and he underwent aortocoronary bypass: left internal mammary to anterior descending, and replacement of the mitral valve with a Labcor No. 31 biological prosthesis, preserving the posterior leaflet of the native valve (non-revascularised DC, non-viable territory).  In the immediate postoperative period he presented a postcardiotomy syndrome with good response to depletive and anti-inflammatory treatment (colchicine for 6 months). The patient remained asymptomatic. In the control echocardiography 6 months after surgery, a 19 x 11 mm thrombus was detected on the atrial side of the septal leaflet of the biological prosthesis. Anticoagulation therapy was optimised. Nineteen days after admission, he presented a fever peak of up to 38.5 oC with no apparent focus. Serial cultures were taken (all negative) and empirical antibiotic treatment was prescribed for 10 days. 25 days after optimisation of anticoagulant treatment, an echocardiographic check-up was performed and it appeared that the thrombus was no longer present.

Two months later the patient presented with an episode of weakness, unilateral loss of vision and nausea. During his admission, the reappearance of the intraprosthetic thrombus was observed, and anticoagulant treatment was optimised again: inflammation parameters and serial cultures were negative. Before discharge, he presented an episode of isolated febrile fever of 37.4 oC, so serial cultures were repeated and TEE was repeated, showing a sessile and mobile endocardial wart on the anterior leaflet of the mitral valve, measuring 8.5 mm. In the area where the thrombus had developed, a new finding was detected: pseudoaneurysm of the mitral valve annulus measuring 20 x 6 mm (high suspicion of endocardial process). Given the suspicion of infective endocarditis in the TEE, empirical antibiotic treatment was started. Cultures were negative, as were serologies and PCR. A PET-CT study was performed which showed images suggestive of infective endocarditis on the mitral prosthetic valve. In addition, a follow-up TEE performed 1 month later showed a new-onset mitral valve annulus perforation: severe periprosthetic insufficiency. The patient required further depletive treatment.

Given the diagnosis of endocarditis with negative blood cultures, in addition to repeating the different cultures, serology for Bartonella, Brucella, Chlamydia, Coxiella, Legionella, Mycoplasma and Borrelia was performed. Serology for Bartonella henselae was positive on two occasions (IgG 1/2048, IgM 1/40). In view of these results, antibiotic treatment was adjusted. In addition, given the presence of a local complication in early prosthetic endocarditis, the patient was proposed for surgery. The patient decided not to undergo surgery. For this reason, oral doxycycline treatment was maintained indefinitely (B. henseale). A control transthoracic echocardiography performed 1 month after the start of treatment revealed a mitral perivalvular abscess with partial "disinsertion" of the mitral annulus rocking motion. Given the patient's decision, medical treatment was optimised again.
