Carcinoid syndrome is most commonly caused by an overproduction of hormones from metastatic midgut tumors and is characterized by diarrhea, flushing, hypotension, and increased airway reactivity. Roughly half of these cases also have carcinoid heart disease associated with fibrous deposition in right-heart structures. In particular, tricuspid and pulmonic valve leaflets become restricted resulting in regurgitant valvulopathies.
The lungs are thought to metabolize and/or reuptake many vasoactive substances and hormones (serotonin, norepinephrine, bradykinin, etc.) which is why the left heart tends to be spared from pathology. Exceptions include right-to-left intracardiac shunting or a very large amount of hormone.
As a cardiac anesthesiologist, visualizing the heart in the field and using the information I gather from transesophageal echocardiography and other invasive monitors helps me determine how the rest of the heart responds to surgical interventions (typically a tricuspid +/- pulmonic valve replacement). This helps me optimize the anesthetic, pharmacotherapy, fluid replacement strategies, etc. As an intensivist, anticipating and managing carcinoid crisis in the perioperative period with octreotide and resuscitative measures is also essential.