Author: Tanner Marshall, MS
Editor: Rishi Desai, MD, MPH, Tanner Marshall, MS Cardiomyopathy translates to “heart muscle disease,” so cardiomyopathy is a broad term used to describe a variety of issues that result from disease of the myocardium, or heart muscle.
When cardiomyopathy develops as a way to compensate for some other underlying disease like hypertension or valve diseases, it’s called secondary cardiomyopathy,
but when it develops all by itself it’s called a primary cardiomyopathy.
Restrictive cardiomyopathy is where the heart muscle is restricted, meaning it becomes stiffer and less compliant. The muscles and size of the ventricles, though, stay about the same size or maybe the only get slightly enlarged.
Normally, when blood fills the ventricles, they’re compliant so they stretch out and allow more blood to fill in. When blood fills into restricted ventricles, though, they aren’t allowed to expand. So stiffer, less compliant ventricles means the ventricles can’t stretch, and less blood fills into the ventricle, which means the heart’s starts to fail to pump out enough blood to the body. So restrictive cardiomyopathy causes heart failure, and since filling happens during diastole, we say this is a type of diastolic heart failure.
Now several mechanisms can lead to stiffer heart muscles and restrictive cardiomyopathies. One of these is amyloidosis. Amyloids are proteins that have been misfolded, and once misfolded they become insoluble and can deposit in various tissues and organs, making them less compliant.
Familial amyloid cardiomyopathy is a genetic disorder where mutant transthyretin protein, or TTR, is misfolded and prone to depositing in the heart tissue. TTR’s a protein that usually circulates in the blood and helps transport thryoxine and retinol. Mutations in TTR are more common in African Americans. Similarly, senile cardiac amyloidosis is where, over time, wild-type, or normal TTR deposits in the heart, and this is typically seen in the elderly.
Sarcoidosis is another cause that involves the formation of granulomas in the heart tissue, which are these collections of immune cells. Yet another is endocardial fibroelastosis, where fibrosis develops in the endocardium, the inner lining of the heart, as well as the subendocardium right under, again making the tissue less compliant. Endocardial fibroelastosis happens most often in children, and is thought to be caused by a variety of diseases and stresses, like infections and even nutritional deficiencies.
Loffler syndrome, where eosinophils accumulate in the lung tissue, can also affect the heart tissue, called Loeffler endocarditis or sometimes loeffler endomyocarditis. In this case eosinophils accumulate in the endocardial layer of the heart tissue, causing inflammation and endocardial fibrosis, making it stiffer and again less compliant.
Also, with hemochromatosis, or iron overload, iron can deposit in the heart tissue, which contributes to restricted ventricular filling.
Finally, radiation of the heart tissue can also lead to restrictive cardiomyopathy. And it’s thought that this is because radiation generates reactive oxygen species in the tissue, which ultimately leads to inflammation over time, and causes myocardial fibrosis, or fibrosis of the heart muscle tissue, which makes the tissue stiffer and more restrictive.
Symptoms of restrictive cardiomyopathy include shortness of breath that worsens over time, exercise intolerance, palpitations, weakness, fatigue, swelling of the legs and feet, and enlargement of the liver and spleen. More uncommon symptoms include fainting spells and chest pain.
For diagnosis, sometimes an electrocardiogram or ECG can be helpful, and people will often have low-amplitude signals, and smaller QRS complexes, due to restricted ventricular contraction. Treatment for restrictive cardiomyopathy will be to treat the underlying cause, if possible. For example, treating hemochromatosis by removing excess iron. In many cases though, the definitive treatment is heart transplant. SUMMARY
All right, so, as a quick recap… Restrictive cardiomyopathy is when the heart muscles become stiff and less compliant. This prevents the heart from filling properly and results in diastolic heart failure where less blood is pumped to the rest of the body. It is caused by numerous disorders that either deposits harmful substances like iron or amyloids in the heart tissue, or fibrosis caused by immune cells or radiation. ECG can be helpful in diagnosing restrictive cardiomyopathy and the treatment is based on treating the disorder that causes it or a heart transplant in extreme cases.
Sources edit
http://emedicine.medscape.com/article/152913-treatment
https://en.wikipedia.org/wiki/Hypertrophic_cardiomyopathy https://en.wikipedia.org/wiki/Dilated_cardiomyopathy