Discussion
Nonbacterial thrombotic endocarditis (NBTE, formerly known as marantic endocarditis) has first been described by Ziegler in 1888, as fibrin thrombi on normal or degenerated cardiac valves4. Postmortem, the histological diagnosis of NBTE is defined by the presence of a mixture of platelets and fibrin on the valvular leaflet without detecting micro-organisms destructing the valve. In clinical routine, NBTE is rarely diagnosed antemortem and is likely to be underdiagnosed and overlooked5 as a definitive histological diagnosis is not possible in most cases. In the presented case, a histological confirmation was also not feasible as it would have endangered the patient without affecting the further management. So, the diagnosis was based on appropriate imaging (echocardiography and CT) combined with the clinical findings. We resigned from additional MRI imaging as it would not have changed the clinical management of the patient.
A large autopsy study from 1976 reports an incidence of 1.6 % of NBTE in the adult autopsy population6. Coagulation abnormalities suggestive of disseminated intravascular coagulation were present in 18.5 % of the cases6. Other autopsy studies described the significantly higher prevalence of NBTE in patients with malignancies than in patients without cancer7,8. The condition is predominantly seen in patients suffering from pancreatic cancer in comparison with other carcinomas. As exemplified by our case, NBTE is significantly more common with more than 10% of all pancreatic cancer patients presenting histological features of the disease in autopsy studies7.
Regarding the anatomical site, the aortic valve is most often affected, followed by the mitral valve and a combination of both the aortic and mitral valves. Affections of the tricuspid or pulmonary valve are very rare reflecting only 3.6% (tricuspid valve) or 0.9% (pulmonary valve) of all cases9. When the tricuspid valve is affected, the vegetations are typically present on the atrial surface and occuring at the coapting edge of the leaflets but without altering valve function9. In the first echocardiography, our patient did not suffer from severe tricuspid insufficiency, but unfortunately in a noticeably short span of time, the regurgitation increased, indicating functional impairment of the valve by the growing mass.
Systemic embolization is known to be the main cause of morbidity in NBTE patients, not only affecting the heart valves but also peripheral intravascular thromboses. Arterial thrombosis with infarction have been described in many peripheral organs, whereas spleen and kidneys were most frequent.6 Our patient suffered from venous thromboembolism (deep vein thrombosis and subsequent pulmonary embolism) in the early stage of the disease and additionally developed peripheral arterial thrombosis most probably driven by the coagulopathy.