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Cardiomyopathies are a group of diseases of the myocardium, which is the muscle layer of the heart wall. The three main types are dilated cardiomyopathy, which is the most common one; as well as hypertrophic, and restrictive cardiomyopathy.
Now, let’s quickly review some anatomy and physiology. The heart wall is made of three layers: the outer layer is the epicardium; the middle and thickest layer is the myocardium, which contracts in a rhythmic way to pump blood; and the inner layer is the endocardium. These layers line the four heart chambers, so the two atria and two ventricles, which are separated by the heart valves at the end of each chamber. First, there are two atrioventricular valves, the mitral or bicuspid valve on the left, and the tricuspid valve on the right. The atrioventricular valves prevent blood from returning to the atria after filling the ventricles. And second, there are two semilunar valves called the aortic valve at the left, and the pulmonary valve at the right. The semilunar valves prevent blood from returning to the ventricles after being pumped out.
Okay, when it comes to the causes of dilated cardiomyopathy, there are many potential causes, which include genetic mutations; cardiotoxic agents, such as alcohol, cocaine, lead, as well as chemotherapeutic medications like doxorubicin and trastuzumab. Dilated cardiomyopathy can also be caused by infections such as human herpesvirus 6, cytomegalovirus, or Lyme disease; nutritional deficiencies, like lack of thiamine; and metabolic disorders, like hyperthyroidism. Sometimes, dilated cardiomyopathy can also be related to pregnancy, called peripartum cardiomyopathy.
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