A left atrial myxoma is a benign tumor that is relatively rare; however, it can have significant clinical implications. A cardiac myxoma is the most common tumor originating from the heart, and a majority of the time the tumor is attached to the interatrial septum by a relatively thin stalk. While it can be located in the right atrium or the ventricles, the most common location for a cardiac myxoma is the left atrium. The tumor can grow large enough to obstruct mitral valve inflow causing hemodynamic changes similar to mitral valve stenosis. Pathologically, the tumor originates from multipotential mesenchymal cells. Approximately 20% of cardiac myxomas arise as part of a genetic syndrome such as the Carney complex.
The diagnosis of left atrial myxoma is made on echocardiography, which can visualize the tumor directly.
The two main concerns in the setting of a left atrial myxoma are the development of congestive heart failure symptoms from mitral inflow obstruction (functional mitral stenosis) and embolization of the tumor resulting in stroke. Interestingly, the symptoms from a left atrial myxoma may be positional. Specifically, when in the upright position the tumor will obstruct mitral inflow more easily. Dyspnea may improve while laying flat for this reason. This phenomenon is called platypnea and can occur with other disorders as well.
Physical examination can reveal a “tumor plop” which is an early diastolic low pitched sound just after the S2 heart sound. This is in contrast to the opening snap of rheumatic mitral valve stenosis, which is high-pitched. A tumor plop may be followed by a low pitched diastolic murmur. If the mitral valve inflow obstruction is significant enough, physical exam findings of congestive heart failure will be present.
Treatment is universally surgical excision. The recurrence rate is low (1-5%).