Nonischemic Cardiomyopathy

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

SYMPTOMS OF NONISCHEMIC CARDIOMYOPATHY

The symptoms experienced are markers of heart failure. Depending on the underlying disease, the symptoms may be mild or severe and progress very slowly or rapidly.

• Breathlessness
• Chest pain or sensation of pressure
• Palpitations or sensation of a rapid and uncomfortable heartbeat
• Swelling in the body especially the feet
• Fainting spells
• Fatigue
• Cough and chest discomfort while lying down

DIAGNOSIS OF NONISCHEMIC CARDIOMYOPATHY

History of the above symptoms combined with a thorough physical examination, focusing on the chest would suggest cardiomyopathy. Certain conditions will have other systems affected like the skin and lungs. Investigations will help to confirm the diagnosis.

• Electrocardiogram (ECG): This measures the electrical activity of the heart and can provide information on the rate and rhythm of the heartbeat in addition to information on any structural abnormalities.
• Chest X-Ray
• Echocardiogram: This is an imaging tool that uses ultrasound waves to generate images of the heart. The procedure involves placing a probe over the chest which helps to visualize the internal structure of the heart. The thickness of the heart muscle walls, the valve structure and blood flow between the different heart chambers can be visualized.
• Cardiac Catheterization: This test involves inserting a thin tube (catheter) through a blood vessel in the groin and pushing it up till it reaches the heart. Through the tip of the tube, several different devices can be inserted. A probe to detect pressure can help identify pressure differences between various heart chambers. A small tissue biopsy sample of the heart can be taken as well. By inserting a dye through the catheter, the vessels surrounding the heart can be examined for any obstruction.
• Cardiac CT and MRI: These are additional non-invasive imaging studies using Radiation (CT) or magnetic field (MRI) to generate images of the heart to look at its structure
• Genetic testing: If a genetic mutation is suspected to be causing the disease, testing of the individual and family members may be attempted.
• Routine blood investigations with additional special tests for detecting markers of a certain disease (iron, vitamin levels, inflammatory markers)

TREATMENT OF NONISCHEMIC CARDIOMYOPATHY

The treatment of the condition depends on the underlying disease. The treatment plan is decided through consultation with a specialist team. The treatment includes both lifestyle changes, medications, devices etc. In certain cases, a heart transplant may be the only long term cure for the disease.  options include

• Low Salt Diet
• Fluid Restriction
• Quit Smoking and Alcohol
• Exercise and maintain healthy weight
• Diuretics to take extra fluid off the body
• Medications to strength the heart muscle
• ICD and Pacemaker
• Heart Valve Surgery
• Heart Transplant

REFERENCES

1. Cooper LT. Definition and classification of the cardiomyopathies. https://www.uptodate.com/contents/search. Accessed June 3, 2019.

1. Cardiomyopathy. National Heart, Lung, and Blood Institute. Accessed June 3, 2019.