Many individuals with RCM experience no symptoms. Symptoms can develop at any age and are primarily associated with heart failure:

Newborns and babies

• Difficulty feeding or poor growth
• Excessive sweating during feeds or activity
• Excessive fussiness
• Fast breathing

Older children and adults

• Shortness of breath and fatigue
• Feeling dizzy or light-headed
• Fainting or passing out (syncope)
• Persistent cough
• Feeling abnormal heart beats (palpitations)

While some children who have RCM experience no symptoms, they may still be at risk for complications of the condition. The most serious is sudden cardiac arrest, which is a loss of heart function caused by a dangerously fast heart rhythm called ventricular tachycardia.

Without immediate emergency treatment, such as CPR and defibrillation, cardiac arrest may lead to death.

When an individual is diagnosed with RCM, there is a 25 to 30 percent chance that an underlying genetic cause will be identified.

Most commonly, the genetic cause results in a condition that runs in a family and affects only the heart. It is possible that parents, siblings and even aunts / uncles or cousins of an individual with RCM may also have this heart muscle condition.

There are other causes of RCM associated with genetic syndromes. Associated conditions can build-up substances in the heart muscle which cause it to become rigid and incapable of relaxing. These conditions include:

• Build-up of abnormal proteins (amyloidosis) in the heart muscle
• Excess iron (hemochromatosis) in the heart
• Other systemic diseases (sarcoidosis)
• Inherited diseases (such as Fabry disease)

It is also possible for the RCM to be idiopathic, meaning the cause is unknown.

The following are possible methods of diagnosing RCM:

• Medical history of heart failure symptoms and rhythm problems
• Physical exam to assess skeletal muscle strength and identify signs of possible cardiac problems
• Echocardiogram – noninvasive ultrasound test that uses sound waves to produce images of the heart
• Blood tests
• Electrocardiogram (EKG or ECG) - quick, painless and noninvasive test in which electrodes are taped to the chest to record the heart’s electrical signals
• Electrophysiologic (EP) testing – physicians insert catheters into the heart to record electrical activity and determine the cause of the rhythm disturbance
• Cardiac MRI (magnetic resonance imaging) - noninvasive medical test that uses magnetic field and radio wave energy to make detailed pictures of the heart’s internal structure
• Exercise stress echo test which involves exercising on a treadmill or stationary cycle under close monitoring
• Genetic Testing — to determine whether or not a genetic mutation is present
• Family history of cardiomyopathy, rhythm problems, sudden cardiac or unexplained death, cardiac surgery or presence of other cardiac disease in relatives.

Echocardiogram is the most common test used to diagnose RCM, as the enlargement of the upper chamber of the heart (atria) is usually visible.

It is recommended that all family members (parents, siblings, children, grandchildren, uncle, aunt, nephew, niece) be evaluated carefully for this form of cardiomyopathy, even if they have no symptoms.

A genetic counselor and / or geneticist can assess the family history and provide information about the chances of a genetic predisposition to cardiomyopathy.

Please read more about genetic testing for cardiomyopathy.

Management and treatment of RCM may be challenging. Treatment is focused on minimizing or preventing symptoms, protecting the child from abnormal heart rhythms and delaying disease progression.

The following may be methods of treatment for your child’s RCM:

• Medications are used to treat symptoms, but there is currently nothing to improve the heart’s ability to relax
• Lifestyle changes – some children will be discouraged from exercise, especially competitive sports
• Surgical procedure(s) to reduce muscle wall thickness

Each individual child’s risk for more serious problems such as sudden cardiac death will be assessed by the doctor, who may recommend an implantable cardioverter-defibrillator (ICD), an automated device placed under the skin that tracks the heart rate and sends electrical signals to the heart if it detects abnormalities. This will reduce the chance of a sudden cardiac death. In some severe cases, a heart transplant may be considered.