In amyloidosis, substances called amyloids deposit in various tissues and organs throughout the body. They accumulate and cause a great deal of damage. One type of amyloid can accumulate in the heart and cause harm to the heart as a whole or to the sections of the heart that it infiltrates.
What is Amyloidosis?
An amyloid is a protein. Amyloidosis is the word for all the diseases where amyloids deposit and accumulate in the tissues and organs, according to David Seldin, M.D., Ph.D., director of the Amyloid Treatment and Research Program at Boston Medical Center in “Harrison’s Principles of Internal Medicine.” There are different types of amyloidosis. In the AL type, the A stands for amyloidosis and the L stands for light chain, which is part of an antibody. The amyloids of this type can accumulate in the heart.
Restrictive Cardiomyopathy
Cardiomyopathy is the disease of the myocardium, or the muscle of the heart. There are three main types of this disorder: dilated, hypertrophic and restrictive. Amyloidosis causes restrictive cardiomyopathy. The heart has four areas called chambers. The ventricles are the two lower chambers. In cardiomyopathy, the heart muscle becomes very thick in one or both of the ventricles. If only one ventricle becomes thick, it is usually the left ventricle, as explained by Malcolm Arnold, M.D., cardiologist at University Hospital in “The Merck Manual for Healthcare Professionals.” Because of the thickness, the heart cannot fill up with the normal volume of blood.
Amyloid Effects in Cardiomyopathy
Sometimes, amyloid infiltrates just part of the heart. If it is in the part that sends the electrical signals, this can block signals and lead to an irregular heartbeat. If amyloid is confined to the heart valves, it prevents the valves from properly closing. It can deposit in the arteries of the heart and interfere with the flow of blood to the heart itself. Deposits in the membrane that surround the heart can restrict the heart from filling. If it affects the pulmonary artery that carries blood from the heart to the lungs, this artery can get so thick it becomes hard for the blood from the right ventricle to pass through it. This can lead to right heart failure, as Brian Hoit, M.D., professor of medicine and physiology and biophysics at Case Western Reserve University writes in “Hurst’s The Heart.”
Diagnosis
The diagnosis of restrictive cardiomyopathy usually includes an echocardiogram, electrocardiogram and chest X-ray, according to Dr. Arnold in “The Merck Manual for Healthcare Professionals.” An echocardiogram is an ultrasound of the heart. It will usually show the thick muscle and very bright amyloid deposits. If an ultrasound does not show the amyloid, physicians can order a CT or MRI. An electrocardiogram (EKG) may show irregular electrical signals within the heart and abnormalities in the left ventricle. A chest X-ray may be normal or it may show an enlarged heart.
Treatment
Dr. Hoit writes about the treatment options in “Hurst’s The Heart.” For people with an irregular heartbeat called atrial fibrillation, physicians prescribe amiodarone and ibultilide. These medications are called anti-arrhythmic because they treat the irregular rhythm and heart rate. If amyloid is blocking the electrical signals to a significant degree, people may need a pacemaker. Melphalan and prednisone are medications for amyloidosis. Melphalan is a chemotherapy medication, while prednisone decreases the number of white blood cells that make the AL type of amyloid.
References
- “Harrison’s Principles of Internal Medicine”; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- “Hurst’s The Heart”; Valentin Fuster, M.D., Ph.D., Robert O’Rourke, M.D., Philip Poole-Wilson, M.D., Richard Walsh, M.D.; 2008
- The Merck Manual for Healthcare Professionals: Restrictive Cardiomyopathy
