Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder that causes muscle weakness and degeneration over time. There are five types of SMA: types 0, 1, 2, 3, and 4. Spinal muscular atrophy type 3 is also referred to as Kugelberg-Welander disease or juvenile SMA. Children with this type of SMA begin showing symptoms after the first year-and-a-half of life. Type 3 SMA has been associated with cardiomyopathy — a disease that affects the heart muscle. People with more severe types of SMA may also experience cardiomyopathy.

What Is Cardiomyopathy?

Cardiomyopathy refers to a group of several conditions that affect the heart muscle. Cardiomyopathy makes it harder for the heart to pump blood to the rest of the body. In some cases, cardiomyopathy can lead to heart failure.

Cardiomyopathy may be acquired (developed as the result of another disease, condition, or contributing factor) or inherited. Although the cause of the disease isn’t always known, muscle conditions such as muscular dystrophy and spinal muscular atrophy can lead to the development of cardiomyopathy.

Heart Problems With Spinal Muscular Atrophy

SMA is a genetic disorder that causes weakness and atrophy (wasting away) of skeletal muscles, which are used for movement. SMA is caused by a mutation in the gene responsible for maintaining motor neurons. The motor neurons are used by the central nervous system to transmit signals between the brain and spinal cord. They tell skeletal muscles to contract, which makes movement possible.

Scientists have recently discovered that SMA may affect other tissues aside from the motor neurons, including the heart. However, evidence is mixed.

Some researchers have identified congenital heart defects in people with SMA, including hypoplastic left heart syndrome (the irregular development of the heart). The cause of hypoplastic left heart syndrome is usually unclear. In most cases, abnormal heart development results from conditions that limit blood flow in the heart, including premature closure of the foramen ovale and cardiomyopathy.

Other research suggests an association between SMA type 3 and arrhythmia (irregular heartbeat) and atrioventricular block (a heart blockage resulting from problems with electrical signals in the heart). A more recent study, however, stated that people with SMA types 2 and 3 do not present with heart dysfunction. This study noted that although cardiomyopathy has been reported in people with Kugelberg-Welander disease, cardiac involvement is often described as secondary to the respiratory problems characteristic of SMA.

A 2017 review of studies suggests that structural defects of the heart may be more common in severe forms of SMA. Heart rhythm problems may be present in people with types 2 and 3, although the authors say more research is needed.

Symptoms of Cardiomyopathy in SMA

Those in the early stages of cardiomyopathy may not have any signs or symptoms. Some people, however, may experience symptoms as the condition progresses, including:

• Breathlessness with physical activity or while at rest
• Cough when lying down
• Fatigue
• Rapid, pounding, or fluttering heartbeat
• Chest discomfort or pressure
• Swelling in the legs, ankles, and feet
• Dizziness, lightheadedness, and fainting
• Bloating of the abdomen (caused by fluid buildup)

According to Mayo Clinic, you should see your doctor if you experience one or more signs or symptoms of cardiomyopathy. Seek emergency medical treatment if you faint, have severe difficulty breathing, or experience chest pain that lasts more than a few minutes.

Treating and Managing Cardiomyopathy in SMA

Treatment for cardiomyopathy may involve medication, surgically implanted devices, or, in severe cases, a heart transplant. The approach taken depends on which type of cardiomyopathy a person has and how severe it is. Cardiomyopathy treatment aims to manage signs and symptoms, prevent the condition from worsening, and reduce the risk of complications. Ask your doctor whether these treatments are appropriate.

Medications might be prescribed to:

• Improve blood flow
• Improve the heart’s ability to pump blood
• Lower blood pressure
• Slow the heart rate
• Remove excess fluid from the body
• Prevent blood clots

Surgically Implanted Devices

Several types of devices can be implanted into the heart to help improve its function and relieve cardiomyopathy symptoms.

Implantable Cardioverter-Defibrillator

An implantable cardioverter-defibrillator (ICD) doesn’t treat cardiomyopathy itself. Instead, it monitors for and corrects abnormal heart rhythms — a serious complication of cardiomyopathy. An ICD works by monitoring the heart’s rhythm and delivering electric shocks as necessary to control abnormal rhythms.

Pacemaker

A pacemaker is a small device placed under the skin of the chest or the abdomen. Like an ICD, a pacemaker uses electrical impulses to control arrhythmias.

Ventricular Assist Device

A ventricular assist device (VAD), which helps blood circulate through the heart, can be used as a long-term treatment or in the short term while waiting for a heart transplant. VADs are usually considered when less-invasive approaches have proven unsuccessful.

Surgery

Surgery to treat cardiomyopathy may include septal myectomy or heart transplant.

Septal Myectomy

Septal myectomy, an open-heart surgery, involves removing part of the thickened septum (heart muscle wall) separating the two bottom heart chambers (ventricles). This surgery improves blood flow through the heart and reduces mitral valve regurgitation (when the heart’s mitral valve doesn’t close tightly, which allows blood to flow backward in the heart).

Heart Transplant

A heart transplant may be necessary for those with end-stage heart failure for whom medications and other treatments are no longer effective.

Nonsurgical Procedures

Nonsurgical procedures used to treat cardiomyopathy include ablation procedures.

Septal Ablation

In septal ablation, a small portion of the thickened heart muscle is destroyed by injecting alcohol through a long, thin tube (called a catheter) into the artery supplying blood to that area of the muscle. Septal ablation allows blood to flow through the area of the heart.

Radiofrequency Ablation

Radiofrequency ablation is used to treat abnormal heart rhythms. In this procedure, catheters are inserted through the blood vessels into the heart. Electrodes at the tips of the catheter transmit energy to damage a small spot of the abnormal heart tissue responsible for the arrhythmias.

You Are Not Alone

It can be challenging living with or caring for a loved one with cardiomyopathy and SMA. The good news is that you’re not alone.

Join mySMAteam, the social network for people with spinal muscular atrophy and their loved ones. Members of this growing community regularly offer support, give advice, and share their stories with others who understand life with SMA.

Do you or a loved one have cardiomyopathy with SMA? Share your experience in the comments below or by starting a new conversation thread on mySMAteam.