Clinical Pearls & Morning Reports
Published October 24, 2018
Nonbacterial thrombotic endocarditis is an immune-mediated phenomenon characterized by the presence of sterile vegetations, composed of bland fibrin–platelet thrombi, that form on valvular leaflets. Nonbacterial thrombotic endocarditis is considered to be an uncommon condition, and it is most often found postmortem, with rates in autopsy series ranging from 0.9 to 1.6%. Read the latest NEJM Case Records of the Massachusetts General Hospital here.
Q: Who is at risk for nonbacterial thrombotic endocarditis?
A: Nonbacterial thrombotic endocarditis typically occurs in patients with advanced cancer and in those with systemic lupus erythematosus. However, it may also complicate other chronic diseases, such as tuberculosis, uremia, and the acquired immunodeficiency syndrome. Nearly 50% of postmortem cases are associated with adenocarcinoma of the lung or ovary, and an additional 25% are associated with hematologic cancer.
Q: Describe the vegetations that result from nonbacterial thrombotic endocarditis.
A: The vegetations that result from nonbacterial thrombotic endocarditis are typically friable and have a high propensity for embolization because of the minimal inflammatory reaction at the site of attachment. They are classically found along valvular coaptation lines (i.e., where the valve edges meet) and are not associated with destruction of valvular tissue. The vegetations are typically small (<1 cm in diameter), broad-based, and irregular in shape, and they are frequently located on the mitral and aortic valves; cases of nonbacterial thrombotic endocarditis involving valves on the right side of the heart are rare. Vegetations on the atrioventricular valves are commonly present on the atrial surface, whereas vegetations on the semilunar valves are usually found on the ventricular surface.
A: The most common initial manifestation of nonbacterial thrombotic endocarditis is an embolic event that results in neurologic symptoms. Patients with nonbacterial thrombotic endocarditis tend to have evidence of multiple, widely distributed brain infarcts on diffusion-weighted MRI, whereas single lesions or focal infarcts are more characteristic of infective endocarditis. Of note, primary cardiac valvular dysfunction is not a common initial manifestation of nonbacterial thrombotic endocarditis.
A: Systemic anticoagulation is recommended to prevent thromboembolism, but it should be noted that, until the underlying process that is driving the immune-mediated valvular deposition is corrected, new vegetations often form despite therapeutic anticoagulation. The anticoagulant of choice is usually unfractionated or low-molecular-weight heparin rather than warfarin, since recurrent thromboembolism can occur in patients with cancer-associated nonbacterial thrombotic endocarditis who are receiving warfarin. The degree of valvular incompetence in patients with nonbacterial thrombotic endocarditis is often not severe and may even be within the normal range (trace or mild). For this reason, surgery (valvular débridement or excision) is rarely indicated, but it may be considered in cases in which the risk–benefit ratio and life expectancy are favorable, with the goal of either preventing recurrent embolization or treating heart failure or severe valvular incompetence.