Benign tumors are a common manifestation of tuberous sclerosis complex (TSC). Heart tumors that result from TSC are called cardiac rhabdomyomas. As their name suggests, rhabdomyomas are composed of tissue normally present in the heart (rhabdo), that grows in a disorganized mass (myoma). In this way they resemble other types of a general class of TSC-related tumors, called hamartomas.
Unlike hamartomas that occur in other organs, cardiac rhabdomyomas are most prevalent in infants and very young children with TSC, and become less prevalent with age. In fact, cardiac rhabdomyomas are the only TSC lesions known to regress over time, in some cases disappearing entirely between early screenings and subsequent examinations. Still, in rare cases of particularly large or numerous tumors, they can disrupt heart rhythm or blood flow through the heart, causing physical impairment and possibly death. Because of this and because cardiac rhabdomyomas provide a critical early sign in the diagnosis of TSC, it is important for doctors to assess heart anatomy and function in individuals suspected of having the disorder or in those previously diagnosed.
Cardiac rhabdomyomas are the earliest detectable clinical indicator of TSC. In some cases, they are identified during prenatal screenings by mid second trimester and can lead to early diagnosis. Approximately 47 to 67 percent of people with TSC have cardiac rhabdomyomas. More importantly in terms of diagnosis, at least 50 percent and possibly a much higher percentage of children with documented rhabdomyomas are ultimately diagnosed with TSC. Because of this diagnostic significance, cardiac rhabdomyomas are considered a major feature in the diagnostic criteria of TSC.
In most people, cardiac rhabdomyomas are small (5-15 mm in diameter) and have no effect on heart function. However, in rare cases where tumors are particularly large or grow on or near heart valves, they can have dramatic effects. Such tumors can obstruct blood flow, impair valve function, or disrupt electrical activity in the heart causing an abnormality of the heart rhythm called an arrhythmia. Although these malfunctions are rare—causing heart failure in just 2 to 4 percent of children with cardiac rhabdomyomas—they are significant and should be evaluated by a pediatric cardiologist.
To detect cardiac rhabdomyomas, doctors use a high-resolution form of ultrasound called an echocardiogram. Cardiologists recommend this exam for all people, especially infants, diagnosed with the disorder and in cases where there is a high suspicion of TSC. They may also recommend a prenatal echocardiogram in cases where parents or immediate family members have TSC. Often, an electrocardiogram (EKG), a reading of the heart's electrical activity, is paired with an echocardiogram to rule out disruptions in heart rhythm that may be caused by a cardiac rhabdomyoma.
Follow-up and Treatment
Once cardiac rhabdomyomas are identified, doctors typically monitor them periodically to ensure that they are regressing. After regression is confirmed, it is seldom necessary for people with small tumors and no detectable heart dysfunction to seek regular heart exams. However, the use of two widely used medications in TSC may make regular screenings necessary. One of these, called adrenocorticotropic hormone (ACTH), commonly used to control infantile spasms, has in rare cases caused cardiac rhabdomyomas to enlarge. Another medication, Tegretol, used to control epileptic seizures in people with TSC, may affect heart rhythm. TSC specialists recommend that before people begin these treatments they undergo an echocardiogram and EKG to establish baseline readings, and then seek regular screenings thereafter.
Cardiac rhabdomyomas are rarely treated because few have significant effects on heart function and most regress over time. However, in rare cases where large cardiac rhabdomyomas impair heart function, cardiac surgeons may surgically remove the offending tumor or tumors.
It is important to remember:
- TSC often causes benign tumors to grow in the heart
- These tumors, called cardiac rhabdomyomas, occur in most people diagnosed with TSC
- Cardiac rhabdomyomas are most prevalent in infants and young children because the tumors typically regress with age
- In most people with TSC, cardiac rhabdomyomas have no effect on heart function
- Large or numerous cardiac rhabdomyomas can affect heart rhythm or blood flow through the heart
- In very rare cases, it becomes necessary to surgically remove problematic rhabdomyomas
- In most cases, TSC specialists simply monitor cardiac rhabdomyomas to ensure that they are regressing, and patients rarely need to follow up after that
- TSC specialists usually recommend that immediate family members of individuals diagnosed with TSC undergo screening for cardiac rhabdomyomas because the tumors serve as indicators of TSC and can aid in diagnosis