Carcinoid heart disease is an important and often serious and life-threatening complication of carcinoid syndrome from functional metastatic neuroendocrine tumors. While the pathogenesis of carcinoid heart disease is not completely understood, we generally believe that its development is related to the amount of serotonin, largely from the metastatic liver burden, to which the right heart valves are exposed over time. However, it is notable that some patients with long-standing carcinoid syndrome and high serotonin levels do not develop carcinoid heart disease while others who seem to have less of a disease burden do.

It is important to be aware of the possibility of a patient with carcinoid syndrome developing carcinoid heart disease and to look for it. If we find subtle early signs, and if we are more aggressive about reducing serotonin production and levels, then perhaps we can forestall the progression of carcinoid heart disease. This has not yet been shown prospectively, but the published prevalence rates of carcinoid heart disease have declined considerably in the era of somatostatin analogue therapy. When we see the early signs of carcinoid heart disease on echocardiograms in patients, we might try to be more aggressive in reducing their serotonin levels one way or another, whether through surgery, hepatic artery embolization techniques, the upward adjustment of somatostatin analogue treatment, or even the addition of telotristat.

Carcinoid heart disease is very rare in the general population, and the echocardiogram should be performed by an individual who has expertise in this particularly unusual type of valvular heart disease. Most ultrasonographers who perform echocardiograms do an outstanding job with assessing the aortic and mitral valves and the left ventricle. But assessing and visualizing the right-sided heart valves (ie, the tricuspid and pulmonic valves) and assessing the right ventricular function in a patient with carcinoid heart disease are, I believe, much more technically challenging. We see patients who have significant carcinoid heart disease clinically, but on recently performed echocardiograms, it appears as though their carcinoid heart disease is very mild or there are minimal findings. Fatigue is often an early clinical indicator of right-sided heart failure, so clinicians who are following patients with carcinoid syndrome should recognize fatigue as a potential prompt for the referral of patients to expert tertiary care centers.  

The surgery that is required to repair or replace heart valves in the setting of carcinoid heart disease can be very difficult, and, when valve replacement is needed, it is better for this to occur earlier as opposed to later. Surgeons should have ample experience with valve replacement in carcinoid heart disease. The anesthesia teams caring for patients with carcinoid syndrome need to be alert to the potential for carcinoid crisis (eg, during debulking) but also to other difficulties that can occur when some degree of right ventricular dysfunction is present.

After valve repair or replacement, there are some reports suggesting that carcinoid heart disease can recur relatively rapidly. I think that it is helpful to know that thrombotic complications on the valve can mimic the echocardiogram findings of valve thickening that are characteristic of carcinoid heart disease, and the former generally respond very well to anticoagulation. Therefore, what might be interpreted as recurrent carcinoid heart disease on a valve may actually be thrombosis.