Malignant carcinoid syndrome. Serotonin concentrations and hemodynamic studies

Abstract

Cardiac catheterizatloh was carried out in a patient with carcinoid syndrome before and during reserpine administration. Simultaneous pulmonary and brachial arterial blood samples failed to reveal a significant difference in plasma serotonin concentration before and during reserpine administration. Although serum serotonin was moderately elevated, absolute levels of plasma (free) serotonin were extremely low in both studies. Clinical deterioration of the patient with signs of increasing congestive heart failure during reserpine therapy was due to excessive depletion of myocardial catecholamines. Unilateral pulmonary artery occlusion demonstrated a normally distensible pulmonary vascular bed despite prolonged exposure to high serum serotonin levels. The cause of cardiovascular lesions in the carcinoid syndrome remains unexplained.