**7. Miscellaneous (Rare) cardiomyopathies**

There are other forms of cardiomyopathy which comprise only a very small percentage of the total (~2–3%) number of cardiomyopathies in children. These cardiomyopathies may have overlapping features with any of the previous types described and include arrhythmogenic right ventricular dysplasia (ARVD), mitochondrial and left ventricular non-compaction cardiomyopathies (LVNC).Patients with ARVD have dilated, poorly functioning right ventricles which have fatty deposits within the walls and are at risk for abnormally fast, lifethreatening heart rhythms (ventricular tachycardia). This myopathy can be diagnosed (usually due to the abnormal rhythms) either in early infancy or later in adolescence/adulthood by echocardiogram or MRI, and its prognosis depends, in part, on the age at presentation.Mito‐ chondrial myopathies are rare and often present early in life. Hearts in the affected patients are often thick-walled (hypertrophic), although dilated hearts with poor function can also occur with this type of myopathy. This cardiomyopathy is caused by abnormalities in the mitochondria of the cells, which are small structures within each cell responsible for generating the energy the cell uses for its normal activities. These cardiomyopathies are often associated with other muscle, liver, neurologic and/or developmental abnormalities and are usually genetically passed from an affected mother to her children.Finally, left ventricular noncompaction (LVNC) cardiomyopathy is characterized by deep trabeculations (or crevices) within muscle of the left ventricular walls. These hearts may have features of both dilated and/ or hypertrophic cardiomyopathy. Conditions associated with LVNC include mitochondrial and metabolic disorders as well as systemic (whole body) processes such as Barth syndrome. Barth syndrome has a constellation of abnormalities including cyclic neutropenia or periodic fluctuations in the white blood cell count (which may not be apparent in early infancy), hypotonia (weak muscles) and LVNC cardiomyopathy. Barth syndrome has recently been linked to an abnormality in the X-chromosome and is passed from mother to son.

generally not useful because the volume of muscle tissue necessary to perform the mitochon‐

Pediatric Cardiomyopathies http://dx.doi.org/10.5772/55820 311

The diagnosis of LVNC can often by strongly suspected when deep crevices or trabeculations are noted with the walls of the left ventricle during an echocardiogram. Very few other cardiac diagnoses have these specific findings. Genetic testing may become more available in the near future to assess identified causes of LVNC especially among male children and those suspected

Currently, there are no therapies that can "cure" cardiomyopathy; however, many treatments are available that can improve symptoms and decrease risk in children with cardiomyopathy. The choice of a specific therapy depends on the type of cardiomyopathy, the clinical condition of the child, the risk of dangerous events and the ability of the child to tolerate the therapy.

The diagnosis of cardiomyopathy affects many areas of a child's life. The following sections outline the general approaches to living with cardiomyopathy. It is important that specific recommendations are developed by the team caring for the child with cardiomyopathy

All children with cardiomyopathy should follow a healthy diet. Certain types of cardiomy‐ opathy are associated with an inability to digest certain types of food, and in these cases, a special diet is developed in consultation with metabolic specialists. In children with the dilated subtype of cardiomyopathy and heart failure, a low salt diet is recommended to avoid fluid retention. Some children with heart failure may not grow well. In these cases, a diet that increases calories is recommended. Children who are taking some medications may have low levels of magnesium or potassium and a diet that has a higher amount of one or both of these two electrolytes may be recommended. Some children with severe heart failure can retain extra body fluid, and it may be necessary to limit the amount that a child can drink to prevent fluid

The long-term outlook of pediatric cardiomyopathy continues to be unpredictable because it occurs with such a wide spectrum of severity and outcome. Even if a child has a family history of the disease, the degree to which he or she is affected can vary considerably from his/her

of having Barth syndrome (see following discussion on the G4.5 mutation testing).

drial analyses can only be safely obtained from arm or leg muscles.

**7.3. Current treatment**

**9. Diet**

**8. Living with cardiomyopathy**

from accumulating in the lungs.

**10. Long term prognosis**

#### **7.1. Symptoms of ARVD, mitochondrial and LVNC cardiomyopathies**

Symptoms (the problems noted by the child and/or family) and signs (the problems detected by your physician) of cardiomyopathy in children are dependent on several factors including the type, cause and severity of the specific cardiomyopathy, the age when the problems started, and the effects of treatment. Since patients with ARVD generally have symptoms consistent with DCM, and patients with mitochondrial or LVNC cardiomyopathies can have symptoms seen with either HCM or DCM, families are encouraged to review the relevant sections written for dilated and hypertrophic cardiomyopathies within this brochure to become familiar with the pertinent symptoms for each of these cardiomyopathy types.

#### **7.2. Diagnosis of ARVD, mitochondrial and LVNC cardiomyopathies**

As with presenting symptoms, the clinical diagnosis of these rare forms of cardiomyopathy will depend on the features of the specific cardiomyopathy. That is, the diagnostic criteria in a child with ARVD will generally follow that of DCM while the mitochondrial and LVNC myopathies will follow that of either DCM or HCM depending on the clinical manifestations of the myopathy. In addition to what is discussed in the diagnostic sections written for the dilated and hypertrophic forms of cardiomyopathy found elsewhere in this brochure, the following comments highlight a few details specific for the diagnosis of each of these rare cardiomyopathies.

The diagnosis of ARVD can be difficult especially in children given its low incidence. However, opposed to the usual form of DCM, which involves the left ventricle to a greater extent, ARVD typically involves the right ventricle preferentially and often times, the clinical suspicion for ARVD can be further explored with MRI (Magnetic Resonance Imaging) which, in many cases, can differentiate fatty deposits from muscle tissue within the wall of the right ventricle that are commonly seen with this disease. The diagnosis can usually be confirmed with visualiza‐ tion of significant fatty deposition within the right ventricular walls (where muscle should be) from biopsy specimens obtained during cardiac catheterization.

Patients with mitochondrial cardiomyopathy often have other associated medical problems such as hearing or vision problems, skeletal muscle weakness in the arm and leg muscles and/ or central nervous system issues including learning problems, developmental delay or loss of developmental milestones. Once suspected, in addition to the cardiac assessment (for DCM or HCM) outlined elsewhere in this brochure, a muscle biopsy performed to evaluate both structure and function of the mitochondria can help verify this diagnosis. A cardiac biopsy is generally not useful because the volume of muscle tissue necessary to perform the mitochon‐ drial analyses can only be safely obtained from arm or leg muscles.

The diagnosis of LVNC can often by strongly suspected when deep crevices or trabeculations are noted with the walls of the left ventricle during an echocardiogram. Very few other cardiac diagnoses have these specific findings. Genetic testing may become more available in the near future to assess identified causes of LVNC especially among male children and those suspected of having Barth syndrome (see following discussion on the G4.5 mutation testing).

#### **7.3. Current treatment**

within muscle of the left ventricular walls. These hearts may have features of both dilated and/ or hypertrophic cardiomyopathy. Conditions associated with LVNC include mitochondrial and metabolic disorders as well as systemic (whole body) processes such as Barth syndrome. Barth syndrome has a constellation of abnormalities including cyclic neutropenia or periodic fluctuations in the white blood cell count (which may not be apparent in early infancy), hypotonia (weak muscles) and LVNC cardiomyopathy. Barth syndrome has recently been

Symptoms (the problems noted by the child and/or family) and signs (the problems detected by your physician) of cardiomyopathy in children are dependent on several factors including the type, cause and severity of the specific cardiomyopathy, the age when the problems started, and the effects of treatment. Since patients with ARVD generally have symptoms consistent with DCM, and patients with mitochondrial or LVNC cardiomyopathies can have symptoms seen with either HCM or DCM, families are encouraged to review the relevant sections written for dilated and hypertrophic cardiomyopathies within this brochure to become familiar with

As with presenting symptoms, the clinical diagnosis of these rare forms of cardiomyopathy will depend on the features of the specific cardiomyopathy. That is, the diagnostic criteria in a child with ARVD will generally follow that of DCM while the mitochondrial and LVNC myopathies will follow that of either DCM or HCM depending on the clinical manifestations of the myopathy. In addition to what is discussed in the diagnostic sections written for the dilated and hypertrophic forms of cardiomyopathy found elsewhere in this brochure, the following comments highlight a few details specific for the diagnosis of each of these rare

The diagnosis of ARVD can be difficult especially in children given its low incidence. However, opposed to the usual form of DCM, which involves the left ventricle to a greater extent, ARVD typically involves the right ventricle preferentially and often times, the clinical suspicion for ARVD can be further explored with MRI (Magnetic Resonance Imaging) which, in many cases, can differentiate fatty deposits from muscle tissue within the wall of the right ventricle that are commonly seen with this disease. The diagnosis can usually be confirmed with visualiza‐ tion of significant fatty deposition within the right ventricular walls (where muscle should be)

Patients with mitochondrial cardiomyopathy often have other associated medical problems such as hearing or vision problems, skeletal muscle weakness in the arm and leg muscles and/ or central nervous system issues including learning problems, developmental delay or loss of developmental milestones. Once suspected, in addition to the cardiac assessment (for DCM or HCM) outlined elsewhere in this brochure, a muscle biopsy performed to evaluate both structure and function of the mitochondria can help verify this diagnosis. A cardiac biopsy is

linked to an abnormality in the X-chromosome and is passed from mother to son.

**7.1. Symptoms of ARVD, mitochondrial and LVNC cardiomyopathies**

the pertinent symptoms for each of these cardiomyopathy types.

from biopsy specimens obtained during cardiac catheterization.

cardiomyopathies.

310 Cardiomyopathies

**7.2. Diagnosis of ARVD, mitochondrial and LVNC cardiomyopathies**

Currently, there are no therapies that can "cure" cardiomyopathy; however, many treatments are available that can improve symptoms and decrease risk in children with cardiomyopathy. The choice of a specific therapy depends on the type of cardiomyopathy, the clinical condition of the child, the risk of dangerous events and the ability of the child to tolerate the therapy.
