Cardiac amyloidosis: Description
Amyloidosis is a rare condition characterized by the extracellular deposition of an abnormal protein called amyloid in various organs.
Amyloid is an abnormal protein built up of fibril proteins (95%), the P component and several glycoproteins. In the microscope amyloid is seen as an extracellular hyaline substance. The three common forms of amyloid are distinguished:
- AL (amyloid light chain) – consists of the light immunoglobulin chains;
- AA (amyloid-associated) produced in the liver;
- Aβ – typical for Alzheimer disease;
- ATTR – common type of amyloid seen in familial amyloidosis;
In cardiac amyloidosis amyloid consists of either light chains (AL) or transthyretin (ATTR). Amyloidosis of the heart muscle usually causes restrictive cardiomyopathy due to the firmness of the myocardium. Abnormal proteins in the heart wall interfere with the conduction of electrical impulses through the heart and therefore results in arrhythmias or heart blocks.
Cardiac amyloidosis may develop as a result of AL amyloidosis or hereditary amyloidosis. Isolated atrial amyloidosis has also been reported.
The disorder may be inherited or acquired. Males are more likely to get affected than females. The disease develops in individuals older than 40.
Symptoms of the heart damage in amyloidosis
Some people may be asymptomatic. When present, symptoms may include:
- Fatigue, weakness, dizziness;
- Palpitations (sensation of feeling heartbeat);
- Episodes of unconsciousness (syncope);
- Shortness of breath, dyspnea;
- Chest pain (angina);
- Swelling of the abdomen, legs, ankles, or other body parts (edema);
- Excessive urination at night;
Familial amyloid cardiomyopathy
FAC is associated with the mutation Val122Ile (replacement of valine by isoleucine at position 122 on chromosome 18) and is common for native African males. FAC is characterized by the deposition of amyloid in the tissues of the heart (mainly the myocardium) that interferes with the conduction of the stimuli and results in the heart block and heart insufficiency. The heart muscle becomes stiff and thick and therefore develops diastolic dysfunction. This means that the cardiomyopathy is of restrictive type. Common signs of cardiomyopathy include arrhythmia and palpitations, chest pain (angina pectoris), fatigue, shortness of breath, episodes of unconsciousness (syncope), swellings of the legs (peripheral edema), nausea and weight loss.
- Atrial fibrillation;
- Congestive heart failure;
- Embolism and stroke;
- Sick sinus syndrome;
- Ventricular arrhythmias;
- Heart block;
- Pericardial tamponade;
See also: Amyloid heart disease
Salt-restricted diet is recommended. It is important to control the fluid volume in the body to avoid the heart insufficiency.
There is no cure for this condition , although liver transplantation in combination with heart transplantation is known to be an effective treatment for ATTR familial amyloidosis.
Auto-stem-cell transplantation is performed in case of AL amyloidosis.
Symptomatic treatment is used to provide a better life quality and avoid the disease progression. Pacemaker implantation is required in case of arrhythmias and heart blocks.
Melphalan and prednisone/dexomethasone may be useful in cardiac amyloidosis. Cyclophosphamise, thalidomide and colchicines sometimes are prescribed.
Heart symptoms may be alleviated with the help of the following medicines:
- Loop diuretics (Lasix);
- Antiarrhythmic drugs (Amiodarone);
- Anticoagulants (Warfarin);