Carcinoid heart disease in patients with midgut neuroendocrine tumours.

Carcinoid heart disease (CHD) is the main complication of carcinoid syndrome (CS) associated with metastatic small intestine neuroendocrine tumours (NETs). The pathophysiology of CHD is partly understood but vasoactive hormones secreted by NETs, especially serotonin, play a major role, leading to the formation of fibrous plaques. These plaque-like deposits involve the right side of the heart in >90% of cases, particularly the tricuspid and pulmonary valves, which become thickened, retracted and immobile, resulting in regurgitation or stenosis. CHD represents a major diagnostic and therapeutic challenge for patients with NET and CS and is associated with increased risk of morbidity and mortality. CHD often occurs 2-5 years after the diagnosis of metastatic NET, but diagnosis of CHD can be delayed as patients are often asymptomatic for a long time despite severe heart valve involvement. Circulating biomarkers (5HIAA, NT-proBNP) are relevant tools but transthoracic echocardiography is the key examination for diagnosis and follow-up of CHD. However, there is no consensus on the optimal indications and frequency of TTE and biomarker dosing regarding screening and diagnosis. Treatment of CHD is complex and requires a multidisciplinary approach. It relies on antitumour treatment, control of CS and surgical valve replacement in cases of severe CHD. However, cardiac surgery is associated with a high risk of mortality, notably due to perioperative carcinoid crisis and right ventricular dysfunction. Timing of surgery is the most crucial point of CHD management and relies on the case-by-case determination of the optimal compromise between tumour progression, cardiac symptoms and CS control.