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HEART MANIFESTATIONS IN TSC

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The primary finding in the hearts of individuals with tuberous sclerosis complex (TSC) is the presence of cardiac (heart) rhabdomyomas. These are non-malignant tumors that can occur anywhere in the heart but tend to show up most on the ventricular and septal walls. About 50% of individuals with TSC have cardiac rhabdomyomas and vice versa: 50% of individuals with cardiac rhabdomyomas have TSC. The presence of multiple, rather than a single, tumors is more consistent with a diagnosis of TSC.

Diagnosis of Cardiac Tumors

Echocardiography (ECG; ultrasound of the heart) is most commonly used for the diagnosis of cardiac tumors. It is a non-invasive, safe, quick and painless test that allows the cardiologist to visualize the interior of the heart.

With the arrival of fetal echocardiography (ultrasound evaluation of the fetal heart), some fetuses can now be diagnosed with TSC before they are even born. In fact, some mothers have been diagnosed with TSC after their fetuses were found to have rhabdomyomas. Because the inheritance pattern of TSC is autosomal dominant (meaning the offspring of an affected person has a 50% percent chance of inheriting the disease), fetal echocardiography may be offered as a screening tool to these individuals as it may detect rhabdomyomas in fetuses as little as 18–20 weeks of development. Some fetuses may have arrhythmias as well (see below) and are found to have TSC and rhabdomyomas when the cause of the abnormal heart rhythm is sought.

Magnetic resonance imaging (MRI) and computerized tomography (CT) are other useful modalities to image intracardiac tumors.

Symptoms and Natural History

Rhabdomyomas are non-cancerous; they do not metastasize (spread to other parts of the body). The symptoms associated with these tumors are largely dependent on their location, number and size. Large tumors within the heart may obstruct the cardiac valves or the great vessels that enter and leave the heart.
 
Most newborns and infants with no major cardiac obstruction are asymptomatic (show no symptoms). Some individuals may have no obvious clinical findings despite extensive cardiac involvement. However, those with tumors large enough to obstruct the ventricular cavity and impede blood flow may develop congestive heart failure (inability of the heart to pump enough blood to the body) or cyanosis (blue discoloration of the skin due to insufficient blood oxygenation), depending on which major valve or blood vessel is involved.

Some rhabdomyomas are located in close proximity to the heart’s electrical conduction system. In about 20% of cases, this may result in significant arrhythmias (abnormal heart rhythm), such as supraventricular tachycardia (SVT, or abnormally fast heart rate) or first to third degree atrio-ventricular block (bradycardia or slow heart rate).

There have been isolated reports of sudden death in children and young adults with TSC that have been attributed to ventricular tachyarrhythmias (VT). These individuals may have palpitations, chest pain or syncope (sudden loss of consciousness). Although these instances are rare, monitoring of individuals with cardiac complaints using echocardiography and Holter monitors (portable echocardiography machines that you can wear around home) is advisable. In cases where VT is attributed to a ventricular rhabdomyoma, surgical resection of the tumor will likely result in resolution of the rhythm disturbance.

Rhabdomyositis, a rare form of cardiomyopathy (poor cardiac muscle function), has been described in individuals with TSC with tumor nodules that are not grossly apparent, but are found microscopically to diffusely involve cardiac muscle fibers. Sudden death from intractable ventricular tachycardia as well as recurrent atrial tachycardia has been attributed to rhabdomyositis.

Fortunately, however, most rhabdomyomas do not grow over time; they either get smaller or remain stable in size. In fact, some tumors decrease in size such that they become no longer visible by echocardiography. A notable exception has been reported for a few infants treated with ACTH (adrenocorticotropic hormone) for infantile spasms (a form of seizures) whose tumors were found to increase in size. In these instances, it would probably be prudent to closely monitor these infants by serial cardiac ultrasound for growth of the rhabdomyomas and/or use another antiepileptic drug (for example, vigabatrin for infantile spasms in TSC).

Management: Screening and Treatment

Cardiac evaluation and screening is recommended for all individuals with TSC who have symptoms related to rhabdomyomas. A baseline echocardiogram to image the heart is indicated in all individuals with TSC regardless of age. For some older individuals, ultrasound imaging may be inadequate and an MRI of the heart may be necessary. For those diagnosed with cardiac tumors, the frequency and necessity for follow-up imaging should be performed at the discretion of a cardiologist and will depend on many factors.  

As pointed out earlier, arrhythmias may occur in individuals with TSC who have cardiac rhabdomyomas. For individuals who are diagnosed with TSC as adults, an arrhythmia may exist due to a rhabdomyoma that was present during childhood but that has since regressed.  A baseline electrocardiogram (EKG) and 24-hour Holter monitoring may be done to diagnose these rhythm disturbances and aid in their follow-up during the course of treatment. 

Because most rhabdomyomas regress in size, watchful monitoring may be all that is necessary in individuals with TSC who do not have significant obstruction. Individuals with TSC who have significant arrhythmias may require treatment with medications or an electrophysiology study with radio-frequency ablation (a special cardiac catheterization procedure).

In the rare instances where hemodynamic compromise is present (severe obstruction, congestive heart failure or cyanosis as explained previously), prompt surgical excision of the tumors may be indicated. If complete excision may severely damage remaining cardiac tissue, partial removal may still provide relief of cardiac symptoms. One must note, however, that since even large tumors may regress in size or disappear completely, the presence of rhabdomyomas without severe obstruction or life-threatening arrhythmias is not necessarily an indication for surgical intervention. In the vast majority of instances, rhabdomyomas do not require surgical intervention.

Written by Regina L. Lantin, M.D., Assistant Professor of Pediatrics, Division of Cardiology, at the University of Texas Houston Medical School.

**Tuberous Sclerosis Alliance Information Sheets are intended to provide basic information about TSC. They are not intended to, nor do they, constitute medical or other advice. Readers are warned not to take any action with regard to medical treatment without first consulting a physician.  The TS Alliance does not promote or recommend any treatment, therapy, institution or health care plan.

Made possible through an educational grant from the Schnurmacher Foundations.  June 2006