The authors report two cases of unexplained active inflammatory endocarditis with totally different clinical presentations. The patients had undergone previous mitral repair surgery and were referred for multiple soft mobile masses on the mitral ring without clinical or laboratory signs of endocarditis. Serologic screening and blood culture results were negative, including those for specific fastidious bacteria, as well as immunologic tests to rule out “nonbacterial thrombotic endocarditis.” Before new surgery, both patients were treated with long-term antibiotic and anticoagulant therapy, with no significant changes in clinical setting and echocardiographic patterns. In neither case was it possible to characterize a specific microorganism: the intraoperative findings were highly evocative of active endocarditis with a macroscopic infiltration of the mitral ring, and culture results from surgical material and valvular tissue were negative.
Infective endocarditis can usually be diagnosed by positive blood culture results and the detection of vegetations on echocardiography. In one third of patients, blood culture results are negative as well as laboratory signs evocative of infective endocarditis, and the differential diagnosis between vegetations and thrombosis may be challenging. Serologic screening and cultures from infected valve tissue are usually able to detect specific etiologies.
We report two unusual cases of patients with soft mobile masses on the mitral valve (MV) after previous repair surgery and without clinical and laboratory signs of endocarditis. Before new surgery, both patients were treated with long-term antibiotic and anticoagulant therapy, with no change in echocardiographic patterns. In neither case were we able to characterize a specific microorganism.
Case Reports
Case 1
A 64-year-old man with a clinical history of prior MV repair underwent new surgical intervention because of recurrent transient ischemic attacks due to vegetations on the MV. No report of surgical findings was available.
Six months before he was admitted to our hospital, echocardiographic follow-up showed new masses on the MV, so the patient received empiric antibiotic and anticoagulation therapy according to the embolic sources detected. Clinical follow-up was characterized by recurrent ischemic events without laboratory signs of infection, notwithstanding the persistence of valvular masses. Three sets of blood culture and thrombophilic and immunologic screening results were normal, including coagulation factors, lipoprotein(a), anticardiolipin and antiphospholipid antibodies, homocysteinemia, lupus-like anticoagulant, protein C, protein S, antiheparin antibodies, β 2 glycoprotein, and β 2 lipoprotein. Serologic test results for Mycoplasma spp, Legionella spp, Bartonella spp, Coxiella burnetii , Brucella spp, and Clamydia spp were negative. Transesophageal echocardiography confirmed multiple masses 20 mm in length on the atrial side of the mitral ring, with soft texture ( Figure 1 A, Video 1 A) at high risk for embolism. No significant mitral stenosis or regurgitation was observed ( Figure 1 B, Video 1 B). A 3-dimensional reconstruction showed the elective involvement of the mitral annulus, with a large thrombus-like vegetation arising from the prosthetic ring ( Figures 2 A and 2 B, Videos 2 A and 2 B). The patient then underwent MV replacement.
The histologic report described neoangiogenesis with inflammatory cell infiltrate. Gram’s method showed rare extracellular organisms compatible with gram-negative bacteria; this finding was suggestive, but not specific, of HACEK group ( Haemophilus parainfluenzae , H aphrophilus , and H paraphrophilus ; Actinobacillus actinomycetemcomitans ; Cardiobacterium hominis ; Eikenella corrodens ; and Kingella spp) microorganism infection.
Case 2
A 63-year-old man with a clinical history of MV repair was admitted to our hospital. Eight months after surgery, echocardiographic follow-up showed multiple masses on the MV, without symptoms. No history of fever or clinical embolism was reported, and no abnormalities of white blood cell count or inflammatory indices were detected. Repeated blood culture and serologic test results for fastidious bacteria were negative, as well as coagulative function and thrombophilic screening. Immunologic tests ruled out any form of “nonbacterial thrombotic endocarditis” (NBTE). Transesophageal echocardiography showed multiple, movable masses 30 mm in length on the atrial side of the mitral prosthetic ring of ambiguous morphologic texture related to vegetation or thrombus ( Figure 3 A, Video 3 A). The entire ring was involved in the inflammatory reaction and surrounded by soft, nonfibrotic tissue ( Figure 3 B, Video 3 A). The leaflets appeared to be thick, but no perforation or loss of tissue was observed, and significant mitral stenosis was absent ( Figure 3 C, Video 3 B). Whole-body computed tomography ruled out subclinical systemic embolism. After 20 days of antibiotic therapy and heparin, the clinical setting and the echocardiographic pattern were unchanged, so the patient underwent new surgical intervention.
The tissue removed was analyzed, and the histologic report showed no microorganisms; it only described a nonspecific fibrinoinflammatory tissue and neutrophilic infiltration with minimal focal necrosis. All bacterial culture results from the prosthetic ring material and valvular tissue were negative.
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