Myxomas

A myxoma is a noncancerous primary tumor, usually irregular in shape and jellylike in consistency.

Half of all primary heart tumors are myxomas. Three fourths of myxomas occur in the left atrium, the chamber of the heart that receives oxygen-rich blood from the lungs. Some types of myxomas tend to run in families. These hereditary myxomas usually develop in young men in their mid-20s. Myxomas that are not hereditary usually develop in women, typically between the ages of 40 and 60. These myxomas are more likely to occur in the left atrium than are hereditary myxomas.

See the figure How a Myxoma Can Block Blood Flow in the Heart.

Myxomas in the left atrium often grow from a stalk and swing freely with the flow of blood, as a tetherball does. As they swing, they may move in and out of the nearby mitral valve, the valve that opens from the left atrium into the left ventricle. This swinging motion may plug and unplug the valve over and over again, so that blood flow stops and starts intermittently.

See the animation How a Myxoma Can Block Blood Flow in the Heart.

Symptoms

When they stand, people with a myxoma in the left atrium may feel short of breath or may faint. With standing, the force of gravity pulls the myxoma into the opening of the mitral valve, blocking blood flow through the heart. This blockage causes transient heart failure. Lying down typically causes the myxoma to move away from the valve and relieves the symptoms.

Pieces of a myxoma or blood clots that form on the surface of the myxoma may break off (becoming emboli), travel through the bloodstream to other organs, and block arteries there. The resulting symptoms depend on which artery is blocked. For example, a blocked artery in the brain may cause a stroke; a blocked artery in the lung may cause pain and coughing up of blood.

Other symptoms of myxomas include fever, weight loss, Raynaud's phenomenon (the fingers and toes become cold and painful when exposed to cold), a low red blood cell count (anemia), a high white blood cell count, and a low platelet count.

Diagnosis and Treatment

Myxomas are suspected based on the symptoms. With a stethoscope, doctors may hear a sound (heart murmur) produced by leakage of blood back through the mitral valve (mitral regurgitation (see Section 3, Chapter 28)). The cause may be damage to the mitral valve by a myxoma (a very rare cause) or damage by rheumatic fever (a relatively more common cause). Doctors can usually distinguish between a tumor and rheumatic fever based on the heart sounds and the person's medical history.

The diagnosis is confirmed by echocardiography. Other procedures, including angiography, computed tomography (CT), magnetic resonance imaging (MRI), and biopsy are sometimes necessary.

Surgical removal of the myxoma usually cures the person.