Idiopathic giant-cell myocarditis
Idiopathic giant-cell myocarditis is a rare form of heart disease with a high rate of fatality within the first year of diagnosis. The cause is unknown, with the only treatment in the vast majority of cases being heart transplantation. Recurrence of the disease is very likely throughout the remainder of the patient's life.
Definition & Facts
Myocarditis is a term used to describe inflammation of the myocardium, the muscle of the heart. Giant-cell myocarditis occurs when this inflammation appears in conjunction with white blood cells that have fused together, known as multinucleate giant cells. The condition is idiopathic, which means it has no known cause.
Diagnosis and treatment both involve the invasive procedures of heart biopsy and heart transplant. As a result, the disease is usually not caught until it has progressed to an advanced stage. The fatality rate for this disease is high with 70% of patients dying within the first year of diagnosis.
Symptoms & Complaints
Swelling of the outer extremities such as the ankles and wrists may also occur (edema). This is due to the weakened heart muscles being unable to circulate blood effectively to the rest of the body, causing fluid buildup and reduced lung function.
More severe symptoms soon appear as the disease progresses. The heart may beat irregularly, which is known as cardiac arrhythmia. The patient may experience an abnormal heart rate in which the heart beats too quickly - tachycardia or too slowly - bradycardia. Tachycardia and bradycardia can result in fainting or lightheadedness.
Eventually, the patient may experience heart failure. This stage is usually the point at which the presence of idiopathic giant-cell myocarditis is discovered. At this point the muscle of the heart will be significantly enlarged. The median life expectancy without treatment will be 6 months from diagnosis.
The muscle of the heart, the myocardium, can become inflamed (a condition called myocarditis). This can happen for a number of reasons such as viral infections, bacterial infections, drug responses, and autoimmune diseases.
In the case of idiopathic giant-cell myocarditis, the inflammation is theorized to result from the presence of a high number of giant cells in the myocardium. A giant cell is an abnormal mass of cells that have been fused together. Most commonly, these cells are macrophages, which are white blood cells that patrol tissues and "eat" foreign material or pathogens they encounter.
The presence of a large amount of giant cells is usually a signal that an infection is occurring. It has been suggested that the presence of autoimmune disorders such as Crohn's disease may increase the risk of developing idiopathic giant-cell myocarditis. There is also a potential link to tumors of the thymus, an organ that produces another subtype of white blood cell called T cells.
Diagnosis & Tests
Myocarditis by itself can be detected through non-invasive means, by noting if the heart is enlarged (a condition called cardiomegaly). But to get a more specific diagnosis of idiopathic giant-cell myocarditis, a physician must perform a biopsy of the myocardium. Tissue from the heart muscle is extracted surgically and then examined with a microscope to see if there is an abnormal amount of giant cells present.
The biopsy is an advanced procedure that requires insertion of a catheter into the blood vessels of the heart, which is called cardiac catheterization. This biopsy is typically not ordered until heart failure has already occurred on the part of the patient. This is an advanced stage of idiopathic giant-cell myocarditis, which means that treatment must not be delayed once this diagnosis has been determined.
Before a biopsy is performed, a physician may order an echocardiogram, or sonogram of the heart, to detect if the enlargement is due to any other causes. This creates three-dimensional images and sometimes animations that the physician can analyze to detect abnormalities in the structure or function of the heart muscles.
Treatment & Therapy
The traditional treatment for idiopathic giant-cell myocarditis is for a surgeon to perform a heart transplant on the patient. This requires the patient to undergo a series of tests to evaluate their emotional and physical ability to receive a donor heart. The patient must also take a course of immunosuppressant drugs to prevent their immune system from rejecting the donor tissue. The donor heart is typically obtained from a recently deceased or brain dead donor.
The heart transplant itself is a complicated procedure that can be performed in a number of ways depending on the suitability of the organ and the patient's condition. After the procedure is complete, the patient will remain on immunosuppressant drugs for the remainder of their life. Myriad side effects can occur, ranging from infection to development of cancer.
Another option for treatment is to forgo the heart transplant and take immunosuppressant medication in conjunction with corticosteroids. This treatment is less efficacious but also less invasive than a heart transplant. This is a newer therapy that is still being tested.
Prevention & Prophylaxis
There is a five-year survival rate of 70% for heart transplant patients. However, fatality rates remain high nonetheless. 70% of patients die within the first year of diagnosis, with the median amount of time that elapses between diagnosis and death being 6 months. By the end of the first year 90% of patients are either deceased or have received a heart transplant.
It is not yet known how to prevent idiopathic giant-cell myocarditis from occurring, but patients with a history of autoimmune disorders may want to be aware that they are at an increased risk for this condition.