Cardiomyopathy refers to an abnormality in the heart muscle which makes it difficult for the heart to effectively pump blood to the rest of the body. One of the most common causes of cardiomyopathy is ischemia or poor blood supply to the heart muscles. Non-ischemic causes of cardiomyopathy are relatively less common but include a diverse group of diseases.
Classification of Nonischemic Cardiomyopathy
The classification is based on the structural type of muscle defect and mechanism through which the heart’s capacity to pump blood is reduced.
- Dilated Cardiomyopathy: this is the most common type. This involves dilation or enlargement of the left ventricle cavity, which occurs as a consequence of lengthening of the heart muscle fibres. This weakens the muscles and reduces the force of contraction. Common causes include alcohol abuse and several drugs for cancer treatment. Genetic causes have also been identified.
- Hypertrophic Cardiomyopathy: this condition is a result of the enlargement of the heart muscle fibres. These enlarged fibres do not function effectively and are unable to pump blood properly. In addition, the enlargement and thickening of muscle fibres may occur along the ventricular septum (the muscle fibres dividing the left and right ventricle), causing obstruction to the blood flowing out of the heart, which also reduces blood flow to the body. This disease is often found to run in families and is found in young athletic men. It is a cause for sudden cardiac death. Certain genetic mutations are linked to the condition.
- Restrictive Cardiomyopathy: this type of cardiomyopathy is less common and occurs due to the development of abnormal rigidity of the heart muscle. The muscle is less elastic and is unable to fully accommodate the normal amount of blood that reaches the heart. The pumping capacity is also reduced. The factors together bring down the supply of blood to the rest of the body. This condition may occur due to the deposition of a substance like iron if found in high levels in the body (Hemochromatosis), or from inflammatory diseases such as Sarcoidosis.
- Arrhythmogenic Right Ventricular Dysplasia: this is a very rare condition where the heart muscle of the right ventricle is replaced with scar tissue. This scar tissue becomes a focus for the generation of abnormal heart rhythms (Arrhythmias). Genetic mutations are found to be causative.
Causes of Nonischemic Cardiomyopathy
- High Blood Pressure
- Genetic Mutations
- Alcohol use
- Cocaine and amphetamine abuse
- Chemotherapy medications and radiation therapy for cancer treatment
- Heart Valve disease
- Chronic rapid heart rate or heart rhythm disorder
- Metabolic Disorders such as obesity, diabetes and thyroid abnormalities
- Deficiency of certain vitamin: most commonly from Vitamin B1 deficiency (Beriberi)
- Pregnancy: Peripartum cardiomyopathy is a form of dilated cardiomyopathy which generally occurs towards the end of pregnancy
- Infection of the heart muscle
- Connective Tissue Disorders such as SLE (systemic lupus erythematosus), scleroderma, dermatomyositis, and polymyositis
- Hemochromatosis or accumulation of iron in the heart muscle
- Sarcoidosis, an inflammatory disorder where multiple lumps of inflammatory cells grow in different parts of the body including the heart
- Amyloidosis, an accumulation of abnormally structured proteins in various organ tissue, including the heart and blood vessels