Carcinoid heart disease
Carcinoid Heart Disease
Carcinoid tumours are rare neuroendocrine malignancies. Carcinoid syndrome occurs when carcinoid tumour metastasises to the liver. Biomamine and peptides, produced by the metastatic tumour cells in the liver, are able to reach the systemic circulation and leads to the classical carcinoid syndrome. This consists of the constellation of diarrhoea, bronchospasm and flushing (1). A large proportion of patients with carcinoid syndrome will eventually develop carcinoid heart disease. Vasoactive substances including 5-hydroxytrptamine (5-HT), secreted by carcinoid metastases in the liver, are able to reach the reach heart and are associated with the deposition of fibrotic plaques on the endocardial surfaces of the heart. Deposition of fibrotic plaques on valvular structures including chordae leads primarily to right sided valvular dysfunction (2,3,4). The development and progression of carcinoid heart disease is related to elevated levels of 5-HT (5,6).
Despite advances in three dimensional echocardiography and other cross sectional modalities over the past decades, two dimensional trans-thoracic remains the stalwart for diagnosis of carcinoid heart disease. Thorough evaluation of right sided heart valves is critical to accurate assessment of carcinoid heart disease.
Typically morphological changes included diffuse or focal thickening of leaflets and chordae. This leads to tethering/retraction of individual leaflets. Leaflets excursion may be impaired and in severe cases will become fixed (7,8)(Panel A). A spectrum of disease from an isolated leaflet which is fixed to the septum to severe retraction and fixation of all three leaflets has been reported (9). Therefore great care must be taken to identify all three leaflets. Functionally, the most common consequence is tricuspid regurgitation. A vena contracta > 0.7cm is a good, semi-quantitative parameter for severe TR (Panel B). Classically, in severe cases, a dense, “Dagger” shaped continuous wave Doppler profile is seen (Panel C). Tricuspid stenosis is usually mild. Quantification of tricuspid stenosis is usually undertaken using a combination of a mean pressure gradient across the tricuspid valve (≥5mmHg indicating severe stenosis) and the pressure half time.
The pulmonary valve is a semi-lunar valve.Morphological features are the same as for the tricuspid valve; thickened valve cusps with varying degrees of retraction and immobility of cusps is typically seen (Panel A). Transthoracic echocardiography evaluation is often challenging. Optimal definition of valve cusps is often difficult as sometimes only one cusp may be visualized. In a Mayo clinic review of 132 patients the most common pulmonary valve abnormality was regurgitation in 81% of cases and stenosis in 53% of cases (7,8,9). Quantification of pulmonary regurgitation by echocardiography in adults is challenging. Current guidelines suggest the use of colour Doppler jet size, continuous wave density and regurgitant fraction as markers of severity (10). Severe regurgitation is usually associated with a large jet wide, dense continuous wave profile coupled with steep deceleration (Panel B).
Aortic and Mitral Valve
Characteristic left sided valvular involvement is thought to occur in up to a third of all cases of carcinoid heart disease (11). Typically diffuse thickening of valve leaflets and sub-chordal apparatus occurs. The usual consequence is the development of valve regurgitation. Although usually mild, severe regurgitation requiring valve replacement has been reported.
Assessment Of Patent Foramen Ovale
The prevalence of PFO in patients with carcinoid heart disease is between 5 and 40% of cases of carcinoid heart disease (11,12). The importance of a PFO is incompletely understood. Left sided carcinoid heart disease was initially thought to be rare as 5-HT and other substances thought involved in the development of carcinoid plaques were deactivated in the lungs. In patients with left sided carcinoid heart disease the presence of a PFO was thought to be a vector for the passage of 5-HT from the right to the left side of the heart. Other causes of left sided carcinoid heart disease include bronchial carcinoid or the presence of very high urinary 5-hydroxyindolacetic acid levels (12). Assessment for a PFO requires the use of “microbubble” contrast echocardiography. Typically 10mls of agitated saline is mixed with 0.5ml of the patients venous blood and 0.5ml of air. Boluses of 5mls of the agitated mixture are injected via a 20 gauge cannula inserted into a large vein in the left antecubital fossa. Cough and Valsalva manoeuvre are performed after introduction of the contrast. Either sub-costal, parasternal short axis or apical 4 chamber views were used depending on optimal visualisation of the atria.
The spectrum of carcinoid heart disease is wide. A variety of different patterns of valve and leaflet involvement has been reported from isolated carcinoid deposits on a single pulmonary cusp to involvement of all four cardiac valves. The application of 3D echocardiography allows identification and visualisation of all three tricuspid leaflets or pulmonary cusps simultaneously which is not available with 2D imaging (9). This allows greater appreciation of the relationship between valvular leaflets, sub-chordal structures and the endocardium
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