Carcinoid heart disease--a hidden complication of neuroendocrine tumours.

Carcinoid heart disease (CHD) develops in serotonin-producing neuroendocrine tumours (NET) due to fibrotic endocardial plaques with associated valve dysfunction leading most often to right-sided heart failure. The classical carcinoid syndrome usually occurs when serotonin-producing NET metastasize to the liver. Up to 50% of those patients will exhibit carcinoid heart disease. The pathophysiological process is not yet completely understood: serotonin is considered to be a major initiator of the fibrotic process, but other tumour secreted factors may contribute to the pathogenesis. Histopathology reveals intact valvular cusps with superimposed fibrotic plaques, leading to thickening and retraction of the valves, causing valvular dysfunction. A high index of clinical suspicion to diagnose CHD is needed since symptoms can be rather non-specific. Transthoracic echocardiography is the gold standard for diagnosis and should probably be performed at the time of diagnosing serotonin-producing NET and then repeated annually. On the other hand, when diagnosing right-heart failure, the presence of CHD and underlying serotonin-producing NET should be taken into account. Therapeutic options include pharmacotherapy for heart failure, control of the systemic carcinoid disease and in selected individuals cardiac valve replacement. The elucidation of the pathologic process is necessary to develop targeted antifibrotic therapeutic agents since CHD seems to be irreversible and associated with poor prognosis.