Ans. is 'a' i.e., Valvular endocardiumCarcinoid Hea DiseaseCarcinoid hea disease is the cardiac manifestation of the systemic syndrome caused by carcinoid tumors. It generally involves the endocardium and valve of the right side of hea.Cardiovascular lesions consist of firm plaque like endocardial fibrous thickenings on the inside surfaces of the cardiac chambers and the tricuspid and pulmonary valves. Occasionally they involve the major blood vessels of the right side, the inferior vena cava and the pulmonary aery. These plaque like thickenings are composed predominantly of smooth muscle cells and sparase collagen fibres embedded in an acid mucopolysaccharide-rich matrix materials. Elastic fibers are not present in the plaque.The most common cardiac manifestation is tricuspid regurgitation. Stenosis of right sided valve may also develop.Why does right sided hea involvement more common ?Carcinoid tumors produce a variety of bioactive products that produce these (above described) hea lesions. Among these, serotonin is most impoant. Serotonin is inactivated during its passage through lung. As you all know, left side of hea recieve blood from pulmonary circulation, left sided hear lesions are uncommon (Because serotonin has already been metabolized in lung).Similarly, gastrointestinal carcinoid tumors do not induce carcinoid hea disease (neither right nor left) as bioactive mediators released into the poal circulation are metabolized in the liver. Therefore carcinoid hea disease is produced by tumors that have extensive hepatic metastasis (liver releases the mediators directly into IVC) or carcinoid tumors of organs that are outside poal circulation (e.g., ovary).