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.