Cardiac rhabdomyoma is a rare and benign mesenchymal tumor of striated muscle origin. It most commonly involves the head and neck. It classifies under cardiac and extracardiac types. Extracardiac further classifies into adult, fetal, and germ cell tumors. Cardiac rhabdomyoma (CR) is the most common pediatric heart tumor, mostly occurring before the age of 1 year. Anatomically, they are considered as hamartomas. Most cardiac rhabdomyomas are associated with tuberous sclerosis (TS) and appear in the ventricular myocardium, the atria, the cavoatrial junction, or the epicardial surface.
Most cardiac rhabdomyomas are multiple and pursue a course of spontaneous regression; surgical resection is not advisable unless the patient is symptomatic. The symptoms develop as a result of the obstruction of blood inflow or outflow, resulting in congestive heart failure. Arrhythmias can also occur ranging from bradycardia secondary to sinus or atrioventricular node (AVN) dysfunction to atrial/ventricular tachycardia, AVN reentrant tachycardia, or ventricular pre-excitation.
Genetic modification during the development of striated muscle may be the cause of rhabdomyoma. There are no other identified causes. Between 80 and 90 % of the cardiac rhabdomyomas are associated with tuberous sclerosis.
Primary cardiac tumors are extremely rare and occur in 0.2% of the children. Cardiac rhabdomyomas are the most common cardiac tumor in children (45%). It is observed both in men and women, without any predilection for races.
existsCardiac rhabdomyoma belongs to the hamartomatous subtype. It is most often identifiable in 20 to 30 weeks of gestation. Tumors are identified more in fetal series than postnatal series. With the advent of imaging technology, the rate of fetal detection is on the rise. The interventricular septum, the left, and the right ventricles, and the atrioventricular valves are usually involved. It grows in the myocardium of the cardiac muscle. It can be sporadic, but a strong clinical association r between cardiac rhabdomyoma and tuberous sclerosis  - an autosomal dominant condition characterized by benign hamartomas in multiple organ systems. Diagnosis of tuberous sclerosis is usually clinical, and further genetic testing looking for TSC1 and TSC2 gene mutations are confirmatory.
Cardiac rhabdomyoma comprises of cells resembling embryonic cardiac muscle cells. The histopathology reveals abnormal myocyte architecture, vacuolization, and spider cells (pathognomic).
History and Physical
Cardiac rhabdomyoma can be identified as a mass in utero using ultrasonography. The presentation can vary from heart blocks, hydrops fetalis, or pericardial effusion. If the tumor is large enough, intrauterine fetal demise can also be present. After birth, they are usually asymptomatic; if symptomatic, they typically present with signs and symptoms of heart failure and ventricular dysfunction from the obstruction of the outflow or inflow of blood.
Dyspnea is one of the major initial patient complaints. Tumors are diagnosed more commonly in fetal series than postnatal series resulting in an increased sensitivity of fetal echocardiograms. Due to its close association with tuberous sclerosis, physical findings of tuberous sclerosis-like ash leaf macules, shagreen patches, or sebaceous adenoma can also be in the patient presentation.
As cardiac rhabdomyoma most commonly correlates with tuberous sclerosis, a baseline 12-lead electrocardiogram (EKG) is necessary at the time of diagnosis, even in the absence of any cardiac symptoms, with routine EKGs every 2 to 5 years thereafter. The imaging modality of choice is echocardiography (ECHO). Cardiac rhabdomyoma presents as multiple, echogenic, and nodular masses in the ventricular myocardium. Cardiac rhabdomyoma can also protrude into the ventricular cavity. They are more homogenous and hyperechoic as compared to the normal myocardium.
The findings can be misinterpreted as a different cardiac tumor-like atrial myxoma if the location is atypical (atria) or there is a single large solitary tumor. Other imaging modalities like cardiac magnetic resonance imaging (MRI) can be also be used as an adjunct to ECHO in cases of equivocal findings. The MRI gives a better delineation of the tumor and can be very helpful in cases of planned surgical resection. It also provides a more reliable estimate of ventricular systolic function.
Treatment / Management
Cardiac rhabdomyomas are asymptomatic and regress spontaneously. In rare instances of hemodynamic compromise and congestive heart failure, pharmacotherapy with angiotensin-converting (ACE) enzyme inhibitors, digitalis, and diuretics is indicated. Prostaglandin E can be used to manage hemodynamic instability in a critically ill newborn. Anti-arrhythmics are useful when there are conduction defects or any other ventricular arrhythmia.
Partial or complete surgical resection of the mass is indicated in cases of hemodynamic compromise and congestive heart failure due to a large tumor. Partial resection is preferred if there is a high risk of damage to myocardial mass or vital structure by complete excision. Orthotopic heart transplantation is considered in extremely rare events when the tumor is very large that it has replaced the normal myocardial tissue.
The differential diagnosis include:
- Cardiac fibroma
- Atrial myxoma
- Inflammatory myofibroblastic tumor
If the patient is asymptomatic, watchful waiting is advised as most tumors regress on their own. If symptomatic, the patient requires admission to the cardiac intensive care unit. The mTOR inhibitors are a consideration in cases associated with tuberous sclerosis.
The patients who have had surgery for the removal of rhabdomyoma have a fair to a good prognosis. The highest risk is amongst cardiac rhabdomyomas. They may grow and obstruct the left ventricular outflow tract, thus causing abnormalities in the flow or may cause ventricular tachycardias or heart blocks.
The presence of fetal cardiac rhabdomyoma may be a sign of tuberous sclerosis, and thus, one should evaluate other structures i.e., the renal or brain parenchyma for tumors; this is because cardiac rhabdomyoma is often the first symptom of tuberous sclerosis, followed by neurological involvement and impairment.
- Arrhythmias (bradycardia and tachycardia)
- Congestive heart failure
- Hemodynamic compromise
Postoperative and Rehabilitation Care
Routine postoperative care like regular dressings and suture removal is necessary. Analgesics like acetaminophen, codeine, oxycodone can help control postoperative pain.
Cardiology and cardiothoracic surgery will consult on these cases.
Deterrence and Patient Education
The patient requires education about the course of the disease. Routine follow-up is recommended to look for any development of the symptoms.
Enhancing Healthcare Team Outcomes
The approach to the management of cardiac rhabdomyoma is interprofessional. Inter-personal communication between the general practitioners, cardiologist, and the cardiothoracic surgeon plays a pivotal role. There is a growing body of evidence for the use of everolimus in the management of cardiac rhabdomyoma, and the pharmacists can guide the proper use of the medication. Every step of the management needs to be communicated to the family, which is also an important part of patient-centered care. Patient safety should always be a priority, which again requires a great team effort and performance.