Heart Health (Cardiology)

Background

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are part of a group of disorders in which there is a problem with the muscle protein dystrophin. Progressive muscle weakness is the hallmark of DMD, with breathing and/or heart failure being the leading causes of death in the second or third decade of life. BMD has a later presentation of muscle weakness and an overall milder course. However, the involvement of heart is common in BMD and often out of proportion to the limb muscle involvement. Death due to heart failure is noted in approximately 10-20% of patients with DMD, and in up to 50% of those with BMD. In addition, approximately 10% of female carriers of dystrophin mutation, either DMD or BMD, develop heart failure even in the absence of any limb muscle involvement.

The disease process in the heart is underway long before symptoms may appear, and early signs of heart failure often go unrecognised due to limitations of mobility. A side effect of steroid medication taken to improve muscle strength for patients with DMD is the risk of developing high blood pressure. Therefore, it is extremely important for that patients with DMD and BMD and carrier females undergo early and regular heart monitoring so as to facilitate early treatment of heart failure. This group of patients should be investigated and managed by a cardiologist with an interest in the management of neuromuscular disorders.

Heart monitoring in patients with DMD/BMD

1. Care of the heart of patients with DMD/BMD should begin at diagnosis. They should be referred to a cardiologist for baseline investigations and long-term follow-up.
2. A complete baseline heart evaluation should include a history, physical examination, electrocardiogram (ECG) and an echocardiogram (2D-Echo). Holter monitoring (24-hour ECG recording) may be required for patients identified to have problems with the rhythm of the heart.
3. Patients with DMD should have regular assessments every two years till age 10, and annually after age 10 or at onset of signs and symptoms of heart failure, if they occur earlier. More frequent monitoring may be required if abnormalities are noted on baseline tests.
4. Patients with BMD should be assessed by cardiologist at diagnosis and typically thereafter every 2 years. More frequent monitoring may be required if symptoms of heart failure develop or abnormalities are noted on baseline tests.
5. Problems with breathing may worsen the condition of the heart. As such it is important that patients with DMD have regular monitoring of breathing/ lung problems.
6. Complete assessment of the heart should be undertaken for patients with DMD/BMD before any planned surgery.
7. DMD patients on steroid therapy need additional monitoring to look for high blood pressure. If their blood pressure is found to be high then the dose of steroids they are taking may need to be changed. Alternatively they may need to start on a specific treatment for the high blood pressure.

Heart monitoring in carriers of DMD/BMD

1. Carriers of DMD/BMD should be made aware of the risks, signs and symptoms of heart failure.
2. All carriers should be referred to a cardiologist for baseline assessment, including history, physical examination, ECG and 2D-Echo, at diagnosis or by adolescence if diagnosed as a child.
3. All carriers should be screened with a complete heart evaluation every 5 years after diagnosis, or more frequently if they have symptoms of heart failure.

Key Points

• DMD/BMD can cause problems with the heart muscle leading to heart failure and even death.
• Carriers of DMD/BMD are at high risk of developing heart disease even in the absence of limb muscle weakness.
• Baseline heart evaluation followed by periodic assessments by a cardiologist with interest in neuromuscular disorders is essential in all patients and carriers of DMD/BMD.
• Care and treatment of breathing/lung problems concurrent to care of the heart is equally important in preventing early heart disease.

More Information

• The Diagnosis and Management of Duchenne Muscular Dystrophy  
  Bushby K et al.
  Part 1: Lancet Neurol. 2010 Jan; 9(1):77-93.
  Part 2: Lancet Neurol. 2010 Feb; 9(2):177-189
• http://www.treat-nmd.eu/care/dmd/diagnosis-management-DMD/

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