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Cardiac fibroma, also known as cardiac fibromatosis, is a rare benign tumor of the heart that occurs primarily in infants and children. Benign tumors are typically a solitary, firm grey-white, non-encapsulated tumor that is composed of fibrous and dense connective tissue. It is most commonly located in the interventricular septum or left ventricular wall. Symptoms depend on the size of the tumor, its location relative to the conduction system, and whether it obstructs blood flow. Two-thirds of children with this tumor are asymptomatic, showing no signs and symptoms. Symptomatic cardiac fibromas may be treated by surgical resection. It is associated with Gorlin syndrome. Benign cardiac tumors are rare, 75% are histologically benign. Cardiac fibromas only occur 4-6%, which is less common compared to myxomas (75%) and rhabdomymoas (5-10%).

The diagnosis of these tumors require physical checkups, imaging studies on the heart, and specialized tests to evaluate the heart. Cardiac fibroma is considered a congenital tumor where an ultrasound prenatal scan may help detect during fetal stage. Surgery is the best treatment for an individual with cardiac fibroma. During this surgery, the tumor is completely removed by the surgeon. The overall prognosis is very good with a surgical removal. There have been 200 cases of cardiac fibroma recorded in the medical literature. Risk factors are still unidentified, but 1 in 30 individuals with Gorlin syndrome are known to be present with cardiac fibroma.

Mechanism
The mechanism behind cardiac fibromas are still unclear. Fibromas have a homogeneous mass of fibroblasts mixed with an abundance of collagen and elastic fibers. These masses represent mesenchymal growth, but lacks other mesenchymal elements, such as blood vessels, cartilage bone, and muscle. They often entrap cardiomyocytes, which are muscle cells that make up the cardiac muscle. Cells are decreasing during this time, while collagen contents are increasing. The growth of cardiac fibromas are slow and produces detrimental physical effects. This is done by infiltrating and replacing the myocardium and protruding into the cavity of the heart. These tumors usually occur within the anterior wall of the left ventricle or the interventricular septum and rarely involves the right ventricle. Large fibromas bulge into the cavity of the chamber, interfering with the functions of heart valves and blood flow through the heart. When the left ventricular is obstructed, the outflow tract may give rise to a failed diagnosis of congenital subaortic stenosis. Moreover, it can cause severe congestive heart failure. Cardiac fibromas may present lymphocyte and monocyte aggregates, as well as areas of calcification, which are shown on a chest x-ray or CT scan. The dimensions of these masses and the location cause clinical symptoms. Fibromas cause ventricular arrhythmias and conduction disturbances that become lethal causing a sudden death.

Signs and Symptoms
Cardiac fibroma is a slow-growing tumor that can cause heart electrical transmission defects and arrhythmias. Some features may be seen in the ventricle wall separating the right and left lower chambers or the ventricle muscle. This tumor is rarely seen in atrial locations. Cardiac fibromas are mostly single and well-circumscribed and the average size of the tumor is circular and is 5 cm. Sometimes signs and symptoms are difficult to find in 35% of individuals. Situations like this, the tumor is incidentally diagnosed during a health checkup for other medical conditions. An individual may have abnormal heart sounds, such as a heart murmur.

In 65% of individuals, signs and symptoms are more obvious due to the large size of the tumor. Also, there is blood flow obstruction, especially into or out of the valves. The valves function becomes affected, which leads to heart failure. An individual might experience bluish skin (cyanosis), severe arrhythmias, dizziness, fainting, and other obstructive symptoms may be present.

Diagnosis
The following tests and exams are taken to diagnose Cardiac fibroma:
 * 1) Family medical history and thorough physical examination that includes examination of the heart. Close attention to abnormal heart sounds is important.
 * 2) Echocardiography: Most valuable diagnosis because this can evaluate the morphology, location and range of the tumor. Also, it can access the degree of blood flow obstruction caused by tumor.
 * 3) Magnetic Resonance Imaging (MRI) and computed tomography CT scan of the heart
 * 4) Electrocardiogram (EKG): this is used to measure electrical activity of the heart and to detect arrhythmias.
 * 5) Electrophysiological studies of an individuals heart to determine where arrhythmia is generated in the heart.
 * 6) Doppler ultrasound to measure the speed and direction of blood flow from sound waves.
 * 7) Tissue biopsy: a pathologist may examine the biopsy under a microscope to suggest a definitive diagnosis. This is considered a gold standard in arriving to a conclusive diagnosis. Biopsy specimens are studied by using Hematoxylin and Eosin staining.

Cause and Prevention
The cause of development for cardiac fibroma is still unknown or unexplained. Some of these cases are observed to be linked to Gorlin syndrome; a complex genetic disorder causing the formation of tumors in various parts of the body. Research is currently being undertaken to identify relevant casual factors. Currently, there are no known methods for preventing cardiac fibroma.

Treatment and Prognosis
Cardiac fibroma is commonly treated through surgical excision procedures. The removal of cardiac tumors require an open heart surgery. During the surgery, the surgeon removes the tumor and tissues around it to reduce the risk of the tumor returning. A heart-lung machine is used to take over the work of the heart and lungs because surgery is complicated and requires a still heart. The recovery is usually between 4-5 days in the hospital and 6 weeks in total. An echocardiogram is taken every year to make sure the tumor has not returned or formed any new growth.

If surgery is too difficult, a heart transplantation is a second option. Continuous observations and checkups are recommended to monitor the condition. In cases of arrhythmias, anti-arrhythmic medication is given before surgical treatments are considered. There has been excellent outcomes for individuals who undergo surgery to remove the tumor. If the tumor is completely resected, individuals will have a disease-free survival. If the tumor is incomplete it will continue to grow and recurrence of symptoms occur.

Research
Literature survey on epidemiology and pathology of cardiac fibroma:

During this study, researchers searched through the literature databases on cardiac fibroma to find factors that predict poor outcomes that lead to death. Researchers found that patients who did not survive were significantly younger than those who did survive. These results suggest that younger individuals diagnosed with cardiac fibroma are associated with a poorer outcome. They found no significant difference between the maximum diameter of the tumor between age groups. Even though younger individuals have smaller hearts, the high ratio of tumor-to-heart sizes may generate low cardiac output, which leads to a poor outcome. Literature revealed that 18 of 178 patients with cardiac fibroma were diagnosed during prenatal and neonatal periods, resulting in the tumor having a certain size regardless of the child's age. These findings suggest that cardiac fibromas may be a congenital disorder.

Successful Surgical Excision of a Large Cardiac Fibroma in an Asymptomatic Child:

A 3-year old girl, who was asymptomatic, underwent a successful surgical excision of a large cardiac fibroma. She had frequent coughs, which led to a chest radiograph. A cardiac mass was found on the echocardiography and later was confirmed by magnetic resonance imaging (MRI). After 24 hours of being monitored, it showed sinus rhythms of normal variability. The mass dimensions were 38 X 28 mm in the apical area of the left ventricle. A surgical procedure was recommended due to the risk of ventricular arrhythmias and sudden cardiac death. The surgery was a success and they were able to remove the entire tumor without any complications. Follow-up evaluations at six-months and a year showed the patient was in good health and no signs of tumor recurrence. Asymptomatic patients with cardiac fibroma becomes controversial because these tumors have the tendency to grow. Situations like this, a surgical removal will be the top recommendation for patients.

Primary cardiac tumors in children: a center's experience:

The Department of Cardiac Surgery Children's Hospital in China conducted a study to analyze different characteristics and outcomes of pediatric patients who have primary cardiac tumors treated in their center. They had sixteen patients with primary cardiac tumors between the ages of 1-13 years. All patients were diagnosed by echocardiography, MRI, and computed tomography (CT). As a result, they were able to successfully remove the mass from 15 patients with cardiopulmonary bypass, whereas partial resection was done in one patient. Unfortunately, one patient died during surgery due to low cardiac output syndrome at 5 days after operation. The pathological examination of the cardiac masses showed that rhabdomyoma is the most frequent tumor in children, followed by myxoma, fibromas, etc. Morbidity of rhabdomyomas and fibromas were reported higher in infancy, while myxomas are more frequent in older children.