Cardiomyopathy

Overview

Cardiomyopathy is a form of heart disease in which the heart is abnormally enlarged, thickened and/or stiffened.

This impairs the heart's ability to pump blood throughout the body effectively and can sometimes lead to heart failure, irregular heartbeats called arrhythmias, and blood clots. In children, cardiomyopathy is most common in infants under 1 year old.

There are two general types of cardiomyopathy: ischemic cardiomyopathy, which results from coronary artery disease, and nonischemic cardiomyopathy.

All cases of cardiomyopathy in children are considered nonischemic, of which there are four main types:

• Dilated Cardiomyopathy (DCM) — Also know as congestive cardiomyopathy, this is the most common form of the disease. It occurs when heart muscle tissue is stretched and enlarged, making it difficult for the heart to function and often causing congestive heart failure. For the most part, the cause of DCM in children remains unknown. It is sometimes caused by viruses such as Coxsackie B viruses, certain diseases, severe anemia or nutritional deficiencies, and rare pregnancy complications. Other cases may be genetic.
• Hypertrophic Cardiomyopathy (HCM) — This is the second most common type of cardiomyopathy and results in excessive thickening of the heart walls. Blood flow is restricted as the heart chambers become smaller and stiffer. Most HCM is due to genetic factors.
• Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) — This is a very rare condition, especially in children, where fatty tissue replaces heart muscle. ARVC is thought to be inherited and is usually found in teenagers or young adults.
• Restrictive Cardiomyopathy (RCM) — This is the least common form of cardiomyopathy and is especially rare in children. RCM affects the ventricles — the lower chambers of the heart — restricting blood flow to the heart. The cause of RCM in children is not known.

Acquired Cardiomyopathy

Although many factors are associated with cardiomyopathy, the exact cause of the disease remains unknown. Many cases are genetic in nature, where the condition is inherited, while others are acquired.

The most common cause of acquired cardiomyopathy is a viral infection called myocarditis, which weakens the heart muscle. Other causes include:

• Infectious diseases
• Diseases that affect the immune system, such as HIV
• Nutritional deficiencies or obesity
• Exposure to toxins such as drugs, alcohol and radiation
• Pregnancy-related complications

Signs & symptoms

Symptoms of cardiomyopathy vary. This is further complicated by the fact that infants and young children are often unable to express how they feel. That said, there are a number of symptoms associated with the different forms of cardiomyopathy:

• Dilated Cardiomyopathy (DCM) — Symptoms in infants include difficulty breathing, poor appetite and slow weight gain. Older children may also have trouble being physically active and become excessively fatigued when exercising.
• Hypertrophic Cardiomyopathy (HCM) — Infants with HCM often have trouble breathing, may sweat excessively and have a poor appetite. Older children may have shortness of breath, dizziness and chest pain. They also may faint or have trouble being physically active.
• Restrictive Cardiomyopathy (RCM) — Although the symptoms of RCM tend to be subtle, some children may have a poor appetite, tire easily, and experience chest pain, an upset stomach and a dry cough.
• Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) — ARVC is very rare in children and symptoms usually don't appear until the teen years or later.

Diagnosis

In some cases, cardiomyopathy is diagnosed when a heart murmur is detected at a routine doctor visit, although children with cardiomyopathy do not always have a heart murmur. Another way of diagnosing cardiomyopathy is through special genetic screening, which may be performed if a family member has the condition. Unfortunately, since cardiomyopathy is hard to detect, many children are not diagnosed until the disease has progressed to the point that they have signs of heart failure.

A number of tests may be used to aid the diagnosis of cardiomyopathy as well as to determine the type of the disease. These include:

• Echocardiogram — This test, which helps doctors determine the type of cardiomyopathy a child has as well as the level of heart dysfunction, uses sound waves to measure the heart's size and shape and creates an image of the heart.
• Computed Tomography (CT or CAT) Scan or Magnetic Resonance Imaging (MRI) — These tests provide a three-dimensional image of the heart.
• Electrocardiogram (ECG or EKG) — By generating a record of the heart's electrical activity, this test can be used to check for irregular heart rhythms, called arrhythmias, and evidence that the heart muscle has been strained.
• Holter Monitor — This is a small, portable device worn for one to three days that continuously records the child's heartbeat. It can be used to detect irregular heart rhythms often associated with dilated, hypertrophic or restrictive cardiomyopathy.
• Electrophysiology (EP) Study — Doctors insert special electrode catheters — long, flexible wires — into veins in the groin area and guide them into the heart. These catheters sense electrical impulses and also may be used to stimulate different areas of the heart and map out the heart's electrical system.
• Radionuclide Ventriculogram — Low-dose radioactive material is injected into a vein that leads to the heart. Then pictures are taken with a special camera, which doctors use to assess heart function.
• Cardiac Catheterization — Flexible plastic tubes, called catheters, are inserted into a vein in the groin area and then guided into the heart so that heart function can be readily assessed. Dye is injected into the catheter to check for blocked arteries.
• Genetic Testing — Blood, tissue, and urine tests may be conducted to check if your child has another genetic disorder associated with the cardiomyopathy.

Prognosis for a child diagnosed with cardiomyopathy depends on the type of cardiomyopathy they have as well as the stage of the disease.

Treatment

Children diagnosed with cardiomyopathy often require aggressive treatment specific to the type of cardiomyopathy they have and the extent of the damage to their hearts. The goal of treatment is to control or prevent congestive heart failure, improve heart function and prevent complications, such as arrhythmias and blood clots.

Treatment options include:

• Drug Therapy — Medications may be used to treat the symptoms of cardiomyopathy. The specific drugs vary by the type of cardiomyopathy.
• Implantation of a Pacemaker or Defibrillator — If drug therapy fails to alleviate heart obstructions or if your child has dangerous arrhythmias, a pacemaker or defibrillator may be inserted under the skin of the chest with wires that go through veins into the heart. The implantation is considered minor surgery requiring a short hospital stay. The pacemaker or defibrillator helps monitor and stabilize the heart.
• Surgery — In some cases surgery is recommended to reduce the symptoms of heart failure.
• Heart Transplant — Cardiomyopathy is the leading reason for heart transplantation in children. When a child is at the "end stage" of the disease and experiencing severe symptoms of heart failure, a heart transplant may be considered. It is a major operation with substantial risks including infection, organ rejection and coronary artery disease.

At this time, there is no cure or treatment for cardiomyopathy that is able to restore the heart to normal. However, some symptoms and complications can be controlled with the treatments listed above. The prognosis for children with cardiomyopathy varies considerably depending on the type of the disease they have and the severity of their symptoms.