A wide range of imaging methods is available for the evaluation of heart involvement by carcinoid tumors. The most important are:
- Echocardiography: This should be the first technique used in cases with suspected CHS. Both the leaflets of the tricuspid valves and those of the pulmonary valves as well as their corresponding subvalvular apparatuses are thickened, often with a clublike appearance. Decreased movement with retraction and fixation without coaptation is observed, so that the valve remains partially open.
Fig.: In these Doppler spectrum echocardiography images we can see a continuous dagger-shaped wave. There is a combination of tricuspid regurgitation and stenosis. The right atrium and ventricle are dilated.
Functionally, there is a combination of regurgitation and stenosis. In cases with severe tricuspid regurgitation, a continuous dagger-shaped wave is seen in the Doppler spectrum. The right atrium and ventricle are dilated and thickened although right ventricular function is usually unaltered. Tricuspid regurgitation causes a pattern of right ventricular volume overload with dilation of the right ventricle and alterations in the movement of the interventricular septum (paradoxical movement of the interventricular septum can be seen). In severe cases, pressure forces secondary to valve dysfunction can cause the foramen ovale to reopen.
The left heart is less often involved due to the filtering effect of the lung parenchyma, as mentioned above, because it deactivates serotonin and its derivatives. Nevertheless, left heart involvement is found in 15% of cases, especially when there is a persistent foramen ovale with a right-left shunt, bronchial carcinoids, or large concentrations of vasoactive substances.
Tricuspid regurgitation is nearly always present (~97%); tricuspid stenosis is present in ~59%, pulmonary artery insufficiency in ~50%, and pulmonary artery stenosis in ~25%.
Transesophageal echocardiography can be useful for evaluating the pulmonary valve and the degree of pulmonary stenosis, which is usually underestimated because of the severe tricuspid regurgitation.
Slight pericardial effusion is seen in up to 10% of cases.
- MRI provides valuable information about both heart anatomy and function. It plays a key role in the evaluation of the pulmonary valve, as echocardiography has limitations at this level.
Fig.: MRI 3C & SA
It can evaluate thickening and immobility of the leaflets of the tricuspid valve, as well as alterations in flow, which are seen as hypointense jets in gradient-echo sequences or in white blood cine-MRI, reflecting regurgitation and stenosis.
Late-enhancement studies after the administration of intravenous contrast material shows areas of hyperintensity that represent fibrosis.
Fig.: MRI-Gd
Fig.: Short-axis late phase Gadolinium Gradient-Echo view showing enhancement and thickening of the tricuspid valve.
MRI offers good spatial resolution, tissue characterization, assessment of structure and valve function, study of cardiac function, and the detection and characterization of metastases to the heart and liver in a single test. It also may be used in the follow-up and in the evaluation of treatment response.
Its main drawback is its limited availability and high cost; furthermore, claustrophobic patients, and those with pacemakers, implantable cardioverter defibrillator, cerebral clips, etc. cannot undergo MRI.
- CT can show valvular thickening, atrial and/or ventricular dilation secondary to valvular problems, and reflux of contrast material in the hepatic veins. If iodinated contrast material is administered intravenously, endocardial fibrosis may enhance.
- Nuclear medicine has three techniques that are useful for the study of carcinoid tumors: Metaiodobenzylguanidine (MIBG), positron emission tomography (PET), and Indium-111 scanning. They can be used for the diagnose and for the follow-up.
- Chest X-rays do not show pathological findings in 50% of cases; nonspecific alterations like increased cardiothoracic index (~20%), pleural effusion (~10%), and lung nodules (~10%) may be seen.
Fig.: Chest X-ray. PA and lateral views. Cardiomegaly is seen, most likely secondary to right ventricle enlargement.