Cardiac amyloidosis

Cardiac amyloidosis is a medical disorder, a type of amyloidosis, caused by deposits of an amyloid protein in the heart tissue, resulting in decreased heart function.

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Causes

Amyloidosis is the buildup of a fibril called amyloid in any tissue in the body. Fibrils are proteins produced in excess and slowly deposited where they replace normal tissue.

Different types of amyloidosis are caused by different types of proteins, such as "AL" and "AA." In cardiac amyloidosis there may be associated conduction disturbances (changes in the way the cardiac electrical impulse is transmitted through the heart).

Cardiac amyloidosis usually occurs during primary (AL) amyloidosis. Primary amyloidosis usually accompanies multiple myeloma, a blood disorder in which too much of a certain type of protein is produced. This excess protein is deposited in the heart and in other organs such as the kidney. Deteriorating kidney function also occurs.

The heart is less often compromised by secondary (AA) amyloidosis. A type of secondary amyloidosis that involves the heart is senile amyloidosis. It is caused by overproduction of a protein different from both the AA and AL types. This protein is deposited mainly in the heart, but can also infiltrate blood vessels. Senile cardiac amyloidosis is becoming more common as the average age of the population increases.

Cardiac amyloidosis is the most typical restrictive cardiomyopathy, and it is also known as “stiff heart syndrome.” Much less frequently, cardiac amyloidosis leads to dilated cardiomyopathy.

Cardiac amyloidosis is more common in men than in women.

Symptoms

• Palpitations (sensation of feeling heart beat)
• Swelling of legs, ankles, or other portion of the body (such as abdominal swelling or enlargement)
• Excessive urination at night
• Fatigue, reduced activity tolerance
• Shortness of breath with activity
• Breathing difficulty while lying down

Signs and tests

Cardiac amyloidosis is difficult to diagnose. The findings from an examination are not specific and may indicate enlargement of the heart and fluid in the lungs.

Listening with a stethoscope may reveal lung crackles, heart murmurs, or other abnormal sounds. The liver may be enlarged and neck veins may be distended. The blood pressure may be low or may drop when rising to a standing position (orthostatic hypotension).

Heart enlargement, congestion of the lungs or the veins in the lungs, decreased movement and/or functioning of the heart, heart failure, or signs of amyloidosis in the heart and other organs may show on the following tests:

• Echocardiogram
• Chest x-ray
• Chest or abdomen CT scan
• Coronary angiography
• Nuclear heart scans (MUGA, RNV)
• Magnetic resonance imaging (MRI)

An ECG may reveal conduction disturbances, arrhythmias such as atrial fibrillation, ventricular tachycardia, or premature and ectopic beats.

An echocardiogram may be used to assess the thickness of the heart wall, the size of the chambers in the heart, and the ability of the heart to fill and pump blood. Sometimes an unusual texture of the heart muscle or the endocardium (the lining of the heart) can be seen as well.

A cardiac biopsy that reveals amyloid confirms the diagnosis. Biopsy of other tissues may also confirm the diagnosis. Amyloidosis is frequently confirmed by biopsy of abdominal fat, kidney, or bone marrow.

Treatment

Physical activity may continue as long as the patient can tolerate it. Diet restrictions vary with the extent of cardiomyopathy and heart failure. These may include salt and/or fluid restrictions.

Diuretics (water pills) may be given to remove excess fluid. Digoxin may be used cautiously to improve heart control in patients with atrial fibrillation. Daily weight measurement may be recommended. A weight gain of 3 or 4 pounds or more over 1 or 2 days can indicate excessive fluid accumulation.

Some people benefit from chemotherapy or prednisone.

A pacemaker may be needed if the conduction system is involved. When heart function is very poor, a heart transplant may be considered for some patients, but not those with AL type amyloidosis since their disease compromises many organs. In one type of secondary amyloidosis, liver transplantation is also required.

Prognosis

Cardiac amyloidosis is a chronic and progressive condition. A cardiologist may estimate the prognosis according to the thickness of the left ventricle and to the degree of restriction in the heart (cardiac stiffness). For primary amyloidosis, the median survival after diagnosis is about 2.1 years.

Complications

• Congestive heart failure
• Atrial fibrillation or ventricular arrhythmias
• Sick sinus syndrome (occasionally)
• Symptomatic cardiac conduction system disease (arrhythmias related to abnormal conduction of impulses through the heart muscle)
• Low blood pressure and dizziness from excessive urination (from medication)
• Increased sensitivity to digoxin with the potential for digoxin toxicity and related arrhythmias
• Ascites (fluid accumulation in the abdomen)