Nonbacterial thrombotic endocarditis


Nonbacterial thrombotic endocarditis

Description, Causes and Risk Factors:

Abbreviation: NBTE.

Non-bacterial thrombotic endocarditis is a disease characterized by the presence of vegetations on cardiac valves, which consist of fibrin and platelet aggregates and are devoid of inflammation or bacteria. NBTE was first described in 1888 by Zeigler, Gross & Friedberg. Incidence of NBTE ranges from 0.3% to 9.3%. The sex distribution of NBTE is equal among males and females.

Over the years NBTE has increasingly been recognized as a condition associated with numerous diseases and is a potentially life-threatening source of thromboembolism to the brain, heart, spleen, kidney and other important organs. In this review we discuss the epidemiology, pathophysiology, clinical features and the evolving role of investigations which now make it possible to establish an ante-mortem diagnosis.

Although the etiology and pathogenesis of NBTE is not fully elucidated, several mechanisms play a role. The common factor is endothelial damage and subsequent exposure of the subendothelial connective tissue to the circulating platelets. The pathogenesis can be divided into factors initiating NBTE and the subsequent development of verrucae. Factors implicated in the initiation are: (a) immune complexes, (b) hypoxia, (c) hypercoagulability and (d) carcinomatosis.

There is a strong association between NBTE and neoplastic disease. An echocardiographic study of 200 living patients with various cancers found evidence of NBTE in approximately 19%, which was 10 times more prevalent than in the control group. In a study of 171 cases of NBTE encountered at autopsy over a period of 22 years, malignancy was detected in 59% of cases. Malignancies most frequently associated with NBTE were adenocarcinomas of the lung, ovary, biliary system, pancreas, and stomach. The neoplasms were frequently mucin-secreting adenocarcinomas. Thus, in evaluating patients with NBTE without a clear etiology, an underlying malignancy must always be excluded.

It is difficult to manage and each case should be individually managed by identifying and treating the underlying pathology. Surgical intervention is not recommended unless the patient is in acute congestive failure.

Symptoms:

Symptoms result from embolization and depend on the organ affected (eg, brain, kidneys, spleen). Fever and a heart murmur are sometimes present.

Diagnosis:

The diagnosis of NBTE is considerably more elusive. There are no markers of the bloodstream and the vegetations are small, easily friable and frequently embolize, leaving only small remnants to be identified on the valve. Cardiac murmurs are frequently absent and there is some evidence that echocardiography is less sensitive for the detection of NBTE. Nevertheless, with recent advances in technology, ante-mortem diagnosis of NBTE is possible.

Treatment:

Even with an established diagnosis, treatment of NBTE is difficult. Correction of the underlying cause is of paramount importance. In patients with advanced and non-curable cancers, surgery is unlikely to influence the final outcome and also not prevent recurrent embolization. In patients with potentially curable cancer, coagulopathy should be corrected and a Multidisciplinary Approach regarding the priority of surgery should be considered.

Anticoagulation remains the mainstay of therapy for NBTE, with recent literature supporting the use of intravenous unfractionated heparin. Caution is necessary as anticoagulation can be detrimental in patients with extensive cerebral infarction. The case for anticoagulant therapy is further strengthened by the notion that Trousseau's syndrome and NBTE have a common substrate of disseminated intravascular coagulation.

There are no guidelines for surgical intervention in patients with NBTE. If the patient is in acute congestive cardiac failure (due to valvular dysfunction) or occurrence of recurrent thromboembolism despite therapeutic anticoagulation then surgical intervention is warranted provided the complications and comorbid conditions does not make the prospect of recovery remote. In hemodynamically stable patients the decision for surgical intervention is difficult and should be avoided whenever possible.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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