**Pediatric Cardiomyopathies**

Aspazija Sofijanova and Olivera Jordanova

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/55820

**1. Introduction**

[18] Goddard, A. A, Pierce, C. S, & Mcleod, K. J. Reversal of lower limb edema by calf muscle pump stimulation. J Cardiopulm Rehabil Prev (2008). , 28, 174-179.

[19] Kennedy, P. M, & Inglis, J. T. Distribution and behavior of glabrous cutaneous recep‐

[20] Stewart, J. M, Karman, C, Montgomery, L. D, & Mcleod, K. J. Plantar vibration im‐ proves leg fluid flow in perimenopausal women. Am J Physiol Integr Comp Physiol

[21] Madhavan, G, Nemcek, M. A, Martinez, D. G, & Mcleod, K. C. Enhancing hemodial‐ ysis efficacy through neuromuscular stimulation. Blood Purif (2009). , 27, 58-63. [22] Pierce, C. S, & Mcleod, K. J. Feasibility of treatment of lower limb edema with calf muscle pump stimulation in chronic heart failure. Eur Cardiovasc Nurs (2009). , 5,

tors in the human foot sole. J Physiol (2002). , 538, 995-1002.

1005; , 288, 623-629.

345-348.

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#### **1.1. Development of the cardiovascular system**

The development of the cardiovascular system is an early embryological event. From fertili‐ zation, it takes eight weeks for the human heart to develop into its definitive fetal structure. During this period the system develops so it can 1) **supply nutrients and oxygen to the fetus,** and 2) **immediately start functionining after birth.**

#### **1.2. Early development of the circulatory system**

#### *1.2.1. Blood islands*

During the third week of gestation angioblastic blood islands of mesoderm (angiogenic clusters) appear in the yolk sac, chorion and body stalk. The innermost cells of these blood islands are hematopoietic cells that give rise to the blood cell lines. The outermost cells give rise to the endothelial cell layer of blood vessels. A series of blood islands eventually coalesce to form blood vessels (fig 1).

#### *1.2.2. Heart tube*

By the middle of the third week of gestation angioblastic blood islands from the splanchnic mesoderm appear and form a plexus of vessels lying deep into the horseshoe-shaped pro‐ spective pericardial cavity (fig 2). These small vessels develop into paired endocardial heart tubes. The splanchnic mesoderm proliferates and develops into the myocardial mantle, which gives rise to the myocardium. The epicardium develops from cells that migrate over the myocardial mantle from areas adjacent to the developing heart (fig 3,4).

© 2013 Sofijanova and Jordanova; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**Figure 3.** Endocardial heart tubes

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**Figure 4.** Splanchnic mesoderm

**Figure 1.** Angioblastic blood islands of mesoderm

**Figure 2.** Horseshoe-shaped prospective pericardial cavity

**Figure 3.** Endocardial heart tubes

**Figure 4.** Splanchnic mesoderm

**Figure 2.** Horseshoe-shaped prospective pericardial cavity

**Figure 1.** Angioblastic blood islands of mesoderm

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The bilateral endocardial heart tubes continue to develop and connect with a pair of vessels, the dorsal aortae, located on either side of the midline. As the embryo develops, the lateral folding and cephalic growth of the embryo shift the endocardial heart tubes medially, ventrally and caudally. They fuse in the midline as a single endocardial heart tube. The endocardial heart tube is surrounded by the myocardial mantle and between these two layers is the cardiac jelly. The resulting heart tube is kept suspended in the pericardial cavity through the dorsal mesocardium. When the single heart tube is formed, the embryo is in the fourth week of gestation, is about 3 mm in length, has 4 - 12 somites, and the neural tube is beginning to form. The heart now begins to beat (fig 5).

supply the yolk sac. The blood drains back to the heart tube via paired vitelline veins. The second circuit is the umbilical (allantoic, placental) extraembryonic circuit. In this instance, the dorsal aortae supply blood to umbilical arteries that in turn bring this now unoxygenated blood back to the placenta. Blood from the placenta is carried to the heart tube via umbilical veins.

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As the endocardial heart tubes fuse, several bulges and sulci appear. From the cephalic end, the bulges are the bulbus cordis (truncus arteriosus and the conus arteriosus), the primitive ventricle, the primitive atrium and the sinus venosus (fig 7.) The veins connect to the heart tube via the sinus venosus, while the paired dorsal aortae arise from aortic arches that in turn arise from the aortic sac. The aortic sac is at the most cephalic end of the bulbus cordis. The sulci are present as the bulboventricular sulcus, between the bulbus cordis and the ventricle,

Then, a rapid growth of the heart tube takes place, and the heart begins to convolute. With this convolution the dorsal mesocardium begins to degenerate. During the process of convolution, the first flexure seen is between the bulbus cordis and the ventricle. The bulbo-ventricular loop that is formed shifts this region of the heart to the right and ventrally. The second flexure, the atrioventricular loop, is between the atrium and the ventricle and this region of the heart is

**1.3. Formation of the primitive four chambered heart**

**Figure 6.** Embryonic circuit forms

and the atrioventricular sulcus, between the atrium and the ventricle.

shifted to the left and dorsally. As growth continues the atria shift cephalically.

**Figure 5.** Endocardial heart tube

#### *1.2.3. Vascular circuits*

As the heart begins to beat, three sets of blood islands coalesce to form three vascular circuits. Within the embryo an embryonic circuit forms (fig 6.)It consists of paired dorsal aortae that arise from the endocardial heart tube and break up into capillary networds that supply blood to the developing embryonic tissues. Blood is drained from these tissues byanterior and posterior cardinal veins that drain into common cardinal veins, which in turn drain into the endocardial heart tube.

Two extraembryonic circuits also form. The first is the vitelline (omphalomesenteric, yolk sac) circuit. In this circuit blood from the dorsal aortae drain into vitelline arteries that in turn

**Figure 6.** Embryonic circuit forms

The bilateral endocardial heart tubes continue to develop and connect with a pair of vessels, the dorsal aortae, located on either side of the midline. As the embryo develops, the lateral folding and cephalic growth of the embryo shift the endocardial heart tubes medially, ventrally and caudally. They fuse in the midline as a single endocardial heart tube. The endocardial heart tube is surrounded by the myocardial mantle and between these two layers is the cardiac jelly. The resulting heart tube is kept suspended in the pericardial cavity through the dorsal mesocardium. When the single heart tube is formed, the embryo is in the fourth week of gestation, is about 3 mm in length, has 4 - 12 somites, and the neural tube is beginning to form.

As the heart begins to beat, three sets of blood islands coalesce to form three vascular circuits. Within the embryo an embryonic circuit forms (fig 6.)It consists of paired dorsal aortae that arise from the endocardial heart tube and break up into capillary networds that supply blood to the developing embryonic tissues. Blood is drained from these tissues byanterior and posterior cardinal veins that drain into common cardinal veins, which in turn drain into the

Two extraembryonic circuits also form. The first is the vitelline (omphalomesenteric, yolk sac) circuit. In this circuit blood from the dorsal aortae drain into vitelline arteries that in turn

The heart now begins to beat (fig 5).

284 Cardiomyopathies

**Figure 5.** Endocardial heart tube

*1.2.3. Vascular circuits*

endocardial heart tube.

supply the yolk sac. The blood drains back to the heart tube via paired vitelline veins. The second circuit is the umbilical (allantoic, placental) extraembryonic circuit. In this instance, the dorsal aortae supply blood to umbilical arteries that in turn bring this now unoxygenated blood back to the placenta. Blood from the placenta is carried to the heart tube via umbilical veins.

#### **1.3. Formation of the primitive four chambered heart**

As the endocardial heart tubes fuse, several bulges and sulci appear. From the cephalic end, the bulges are the bulbus cordis (truncus arteriosus and the conus arteriosus), the primitive ventricle, the primitive atrium and the sinus venosus (fig 7.) The veins connect to the heart tube via the sinus venosus, while the paired dorsal aortae arise from aortic arches that in turn arise from the aortic sac. The aortic sac is at the most cephalic end of the bulbus cordis. The sulci are present as the bulboventricular sulcus, between the bulbus cordis and the ventricle, and the atrioventricular sulcus, between the atrium and the ventricle.

Then, a rapid growth of the heart tube takes place, and the heart begins to convolute. With this convolution the dorsal mesocardium begins to degenerate. During the process of convolution, the first flexure seen is between the bulbus cordis and the ventricle. The bulbo-ventricular loop that is formed shifts this region of the heart to the right and ventrally. The second flexure, the atrioventricular loop, is between the atrium and the ventricle and this region of the heart is shifted to the left and dorsally. As growth continues the atria shift cephalically.

**Figure 7.** Convolution of the Heart Tube

The sinus venosus gradually shifts to the right to empty into the right atrium. The bulboventricular sulcus is represented inside the heart as the bulbo-ventricular flange. The bulboventricular flange and the muscular interventricular septum begin to separate the primitive ventricle (which will become the left ventricle) from the proximal bulbus cordis (which will become the definitive right ventricle). The atria continue to grow, and bulge forward on either side of the bulbus cordis, and shift the bulbus medially. With increased blood flow the bulboventricular flange regresses. Thus, the primitive four-chambered heart is formed and blood flows from the veins to sinus venosus, to atria, to ventricles, to conus, to truncus, to aortic sac, to dorsal aorta.

Now the enlarging liver encroaches upon the developing vitelline and umbilical veins and gradually all the blood will drain to the proximal right vitelline vein. The distal vitelline veins will give rise to the portal system. The left umbilical vein remains and drains into the ductus venosus, a shunt which allows blood to bypass the developing liver.

foramen primum. As the septum reaches the endocardial cushions closing foramen primum, a second opening, foramen secundum appears in septum primum. As foramen secundum enlarges, a second septum, septum secundum forms to the right of septum primum. Septum secundum forms an incomplete partition (lying to the right of foramen secundum) which leaves an opening, the foramen ovale. The remaining portions of septum primum become the

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Concurrently, the sinus venosus has shifted to the right as the proximal portions of the left vitelline and umbilical veins are obliterated by the liver. The right sinus venosus becomes incorporated into the right atrium forming the smooth portion of the right atrium. The primitive right atrium is seen in the adult as the rough portion (auricle) of the right atrium. The remainder of the left sinus horn is the coronary sinus and the oblique vein (of Marshall)

On the left side, the primitive atrium is enlarged by the incorporation of tissue from the original, single pulmonary vein and its proximal branches. This incorporated tissue is the adult smooth left atrial wall through which four pulmonary veins empty independently. The

trabeculated left atrial appendage originated from the primitive left atrium.

valve of foramen ovale (fig 8).

**Figure 8.** Atrial Septation

in the adult heart (fig 9).

#### **1.4. Septation of the heart**

During the second month, the heart begins to septate into two atria, two ventricles, the ascending aorta and the pulmonary trunk.

#### *1.4.1. Atrial septation*

Endocardial cushions develop in the dorsal (inferior) and ventral (superior) walls of the heart. These grow toward each other as the cardiac jelly mesenchyme proliferates deep to the endocardium. These cushions fuse and divide the common AV canal into the left and right AV canals.

At the same time there is a developing septum from the dorsocranial atrial wall that grows toward the cushions. This is the septum primum, and the intervening space is called the

**Figure 8.** Atrial Septation

The sinus venosus gradually shifts to the right to empty into the right atrium. The bulboventricular sulcus is represented inside the heart as the bulbo-ventricular flange. The bulboventricular flange and the muscular interventricular septum begin to separate the primitive ventricle (which will become the left ventricle) from the proximal bulbus cordis (which will become the definitive right ventricle). The atria continue to grow, and bulge forward on either side of the bulbus cordis, and shift the bulbus medially. With increased blood flow the bulboventricular flange regresses. Thus, the primitive four-chambered heart is formed and blood flows from the veins to sinus venosus, to atria, to ventricles, to conus, to truncus, to aortic sac,

Now the enlarging liver encroaches upon the developing vitelline and umbilical veins and gradually all the blood will drain to the proximal right vitelline vein. The distal vitelline veins will give rise to the portal system. The left umbilical vein remains and drains into the ductus

During the second month, the heart begins to septate into two atria, two ventricles, the

Endocardial cushions develop in the dorsal (inferior) and ventral (superior) walls of the heart. These grow toward each other as the cardiac jelly mesenchyme proliferates deep to the endocardium. These cushions fuse and divide the common AV canal into the left and right AV

At the same time there is a developing septum from the dorsocranial atrial wall that grows toward the cushions. This is the septum primum, and the intervening space is called the

venosus, a shunt which allows blood to bypass the developing liver.

to dorsal aorta.

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**1.4. Septation of the heart**

**Figure 7.** Convolution of the Heart Tube

*1.4.1. Atrial septation*

canals.

ascending aorta and the pulmonary trunk.

foramen primum. As the septum reaches the endocardial cushions closing foramen primum, a second opening, foramen secundum appears in septum primum. As foramen secundum enlarges, a second septum, septum secundum forms to the right of septum primum. Septum secundum forms an incomplete partition (lying to the right of foramen secundum) which leaves an opening, the foramen ovale. The remaining portions of septum primum become the valve of foramen ovale (fig 8).

Concurrently, the sinus venosus has shifted to the right as the proximal portions of the left vitelline and umbilical veins are obliterated by the liver. The right sinus venosus becomes incorporated into the right atrium forming the smooth portion of the right atrium. The primitive right atrium is seen in the adult as the rough portion (auricle) of the right atrium. The remainder of the left sinus horn is the coronary sinus and the oblique vein (of Marshall) in the adult heart (fig 9).

On the left side, the primitive atrium is enlarged by the incorporation of tissue from the original, single pulmonary vein and its proximal branches. This incorporated tissue is the adult smooth left atrial wall through which four pulmonary veins empty independently. The trabeculated left atrial appendage originated from the primitive left atrium.

*1.4.3. Septation of the bulbus cordis*

migrate into these regions (fig 11).

**Figure 11.** Septation of the Bulbus Cordis

*1.4.4. Cardiac valve fromation*

180o

Truncal swellings (ridges) appear first as bulges in the truncus on the right superior and the left inferior walls. They enlarge and fuse in the midline to form the truncal (aorticopulmonary) septum. This septum spirals as it develops distally, separating the distal pulmonary artery from the aorta. At the same time, right dorsal and left ventral conal ridges form and fuse in the midline. The conal septum helps dividing the proximal aorta from the pulmonary artery and contributes to the membranous IV septum. The truncal and conal septa fuse to form a

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 spiral and together definitively form the aorta and the pulmonary artery. Cells that contribute to the conal and the truncal septa are in part derived from neural crest cells that

Semilunar valves develop in the aorta and pulmonary artery as localized swellings of endo‐ cardial tissue. The atrioventricular valves develop as subendocardial and endocardial tissues and project into the AV canal. These bulges are excavated from the ventricular side and invaded by muscle. Eventually, all the muscle, except that remaining as papillary muscle,

#### *1.4.2. Ventricular septation*

The muscular interventricular septum grows as a ridge of tissue from the caudal heart wall toward the fused endocardial cushions. The remaining opening is the interventricular (IV) foramen. The IV foramen is closed by the conal ridges, outgrowth of the inferior endocar‐ dial cushion, the right tubercle, and connective tissue from the muscular interventricular septum. This portion of the I.V. septum is called the membranous part of the interventric‐ ular septum (fig 10).

**Figure 10.** Ventricular Septation

#### *1.4.3. Septation of the bulbus cordis*

Truncal swellings (ridges) appear first as bulges in the truncus on the right superior and the left inferior walls. They enlarge and fuse in the midline to form the truncal (aorticopulmonary) septum. This septum spirals as it develops distally, separating the distal pulmonary artery from the aorta. At the same time, right dorsal and left ventral conal ridges form and fuse in the midline. The conal septum helps dividing the proximal aorta from the pulmonary artery and contributes to the membranous IV septum. The truncal and conal septa fuse to form a 180o spiral and together definitively form the aorta and the pulmonary artery. Cells that contribute to the conal and the truncal septa are in part derived from neural crest cells that migrate into these regions (fig 11).

**Figure 11.** Septation of the Bulbus Cordis

#### *1.4.4. Cardiac valve fromation*

*1.4.2. Ventricular septation*

**Figure 9.** Atrial Development

288 Cardiomyopathies

ular septum (fig 10).

**Figure 10.** Ventricular Septation

The muscular interventricular septum grows as a ridge of tissue from the caudal heart wall toward the fused endocardial cushions. The remaining opening is the interventricular (IV) foramen. The IV foramen is closed by the conal ridges, outgrowth of the inferior endocar‐ dial cushion, the right tubercle, and connective tissue from the muscular interventricular septum. This portion of the I.V. septum is called the membranous part of the interventric‐

> Semilunar valves develop in the aorta and pulmonary artery as localized swellings of endo‐ cardial tissue. The atrioventricular valves develop as subendocardial and endocardial tissues and project into the AV canal. These bulges are excavated from the ventricular side and invaded by muscle. Eventually, all the muscle, except that remaining as papillary muscle,

disappear and three cusps of the right AV (tricuspid) valve, and two cusps of the left AV (mitral) valve remain as fibrous structures.

#### *1.4.5. Development of the major arteries*

The six pairs of aortic arches, develop in a cephalocaudal direction and interconnect the ventral aortic roots and the dorsal aorta. They are never all present in the developing human heart. Of the six pairs of aortic arches, most of the first, second and fifth arches disappear (fig 12).

**Figure 13.** Development of the Veins

**Figure 14.** Development of Azygos Veins

well as the azygos and hemiazygos viens (fig 14).

In the trunk, one set of veins develops from the posterior cardinal veins and veins that develop from it later in development, such as the subcardinal, supracardinal, and sacrocardinal veins. These veins will give rise to the inferior vena cava, the renal, adrenal and gonadal veins, as

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The superior mesenteric vein (and perhaps the splenic vien) as well as the veins to the liver develop from the vitelline (omphlomesenteric) veins. The ductus venosus develops as a new

structure that connects the left umbilical vein with the inferior vena cava (fig 12).

#### *1.4.6. Development of the veins*

The veins develop from the three major vascular circuits. As with the arteries they develop in a cephalocaudal direction and as a consequence the precursors to the veins are never all present at the same time. In addition, as new structures develop the course of veins changes.

In considering the development of the veins, the veins to the head are derived from the anterior cardinal veins. New channels also develop such as the thymicothyroid anastomoses and the external jugular veins and give rise to veins of the head and neck (fig 13).

**Figure 13.** Development of the Veins

disappear and three cusps of the right AV (tricuspid) valve, and two cusps of the left AV

The six pairs of aortic arches, develop in a cephalocaudal direction and interconnect the ventral aortic roots and the dorsal aorta. They are never all present in the developing human heart. Of the six pairs of aortic arches, most of the first, second and fifth arches disappear (fig 12).

The veins develop from the three major vascular circuits. As with the arteries they develop in a cephalocaudal direction and as a consequence the precursors to the veins are never all present

In considering the development of the veins, the veins to the head are derived from the anterior cardinal veins. New channels also develop such as the thymicothyroid anastomoses and the

at the same time. In addition, as new structures develop the course of veins changes.

external jugular veins and give rise to veins of the head and neck (fig 13).

(mitral) valve remain as fibrous structures.

*1.4.5. Development of the major arteries*

290 Cardiomyopathies

**Figure 12.** Development of the Major Arteries

*1.4.6. Development of the veins*

In the trunk, one set of veins develops from the posterior cardinal veins and veins that develop from it later in development, such as the subcardinal, supracardinal, and sacrocardinal veins. These veins will give rise to the inferior vena cava, the renal, adrenal and gonadal veins, as well as the azygos and hemiazygos viens (fig 14).

**Figure 14.** Development of Azygos Veins

The superior mesenteric vein (and perhaps the splenic vien) as well as the veins to the liver develop from the vitelline (omphlomesenteric) veins. The ductus venosus develops as a new structure that connects the left umbilical vein with the inferior vena cava (fig 12).

### **2. The cardiomyopathies**

Cardiomyopathy is a chronic disease of the heart muscle (myocardium), in which the muscle is abnormally enlarged, thickened, and/or stiffened. The weakened heart muscle loses the ability to pump blood effectively, resulting in irregular heartbeats (arrhythmias) and possibly even heart failure. Cardiomyopathy, a disease of the heart muscle, primari‐ ly affects the left ventricle, which is the main pumping chamber of the heart. Usually, cardiomyopathy begins in the heart's lower chambers (the ventricles), but in severe cases can affect the upper chambers, or atria.The disease is often associated with inadequate heart pumping and other heart function abnormalities. Cardiomyopathy is not common but it can be severely disabling or fatal. Most people are only mildly affected by cardiomy‐ opathy and can lead relatively normal lives.However, people who have severe heart failure may need a heart transplant.Cardiomyopathy is a heart condition that not only affects middle-aged and elderly persons, but can also affect infants, children, and adolescents. Cardiomyopathy is classified as either "ischemic" or "nonischemic". All cases related to children and teenagers are considered "nonischemic" cardiomyopathy. Non-ischemic cardiomyopathy predominately involves the heart's abnormal structure and function. It does not involve the hardening of arteries on the heart surface typically associated with ischemic cardiomyopathy. Nonischemic cardiomyopathy can then be broken down into: 1) "primary cardiomyopathy" where the heart is predominately affected and the cause may be due to infectious agents or genetic disorders and 2) "secondary cardiomyopathy" where the heart is affected due to complications from another disease affecting the body (i.e. HIV, cancer, muscular dystrophy or cystic fibrosis).Cardiomyopathy is nondiscriminatory in that it can affect any adult or child at any stage of their life. It is not gender, geographic, race or age specific. It is a particularly rare disease when diagnosed in infants and young children. Cardiomyopathy continues to be the leading reason for heart transplants in children.Pediatric cardiomyopathy is a rare heart condition that affects infants and children. Specifically, cardiomyopathy means disease of the heart muscle (myocardium). Several different types of cardiomyopathy exist and the specific symptoms vary from case to case. In some cases, no symptoms may be present (asymptomatic); in many cases, cardiomyop‐ athy is a progressive condition that may result in an impaired ability of the heart to pump blood; fatigue; heart block; irregular heartbeats (tachycardia); and, potentially, heart failure and sudden cardiac death.There are numerous causes for a complex disease such as cardiomyopathy. For the majority of diagnosed children, the exact cause remains un‐ known (termed "idiopathic"). In some cases, it may be related to an inherited condition such as a family history of cardiomyopathy or a genetic disorder such as fatty acid oxidation, Barth syndrome, orNoonan syndrome. Cardiomyopathy can also be a conse‐ quence of another disease or toxin where other organs are affected. Possible causes include viral infections (Coxsackie B - CVB), auto-immune diseases during pregnancy, the buildup of proteins in the heart muscle (amyloidosis), and an excess of iron in the heart (hemochromatosis). Excessive use of alcohol, contact with certain toxins, complications from AIDS, and the use of some therapeutic drugs (i.e. doxorubicin) to treat cancer can also contribute to the development of the disease.

**3. Pediatric cardiomyopathies**

and geneticist.

ronmental factors play a greater role in adult cardiomyopathy.

to have a normal heart and be asymptomatic until puberty.

Pediatric cardiomyopathy is a rare heart condition that affects infants and children.There is a vast amount of literature on adult cardiomyopathy but not all of the information is relevant to children diagnosed with the disease. Unfortunately, there has been little research and focus on pediatric cardiomyopathy over the years. Consequently, the causes are not well understood. Pediatric cardiomyopathy is more likely to be due to genetic factors while lifestyle or envi‐

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In rare cases, pediatric cardiomyopathy may be a symptom of a larger genetic disorder that may not be immediately detected. For example, when an infant or young child is diagnosed with dilated cardiomyopathy, a rare genetic heart disease called Barth Syndrome or a mito‐ chondrial defect (i.e. Kearns-Sayre syndrome) may be the cause. Similarly, a child with severe hypertrophic cardiomyopathy may actually have Noonan Syndrome, Pompe disease (type II glycogen storage disease), a fatty acid oxidation disorder, or mitochondrial HCM. It is therefore important for any diagnosed child to be properly evaluated for other suspected genetic disorders. A thorough evaluation remains a complicated and expensive process due to the large number of rare genetic causes, the broad range of symptoms and the existence of many specialized biochemical, enzymatic and genetic tests. Verifying a diagnosis may require getting additional blood, urine or tissue tests and consulting other specialists such as a neurologist

Cardiomyopathy in children may also present differently from diagnosed teenagers or adult. It is considered unusual when an infant or a child is diagnosed with symptoms at such a young age. Typically, symptoms are not apparent until the late teens or adult years when most patients are diagnosed. With hypertrophic cardiomyopathy, the disease commonly develops in association with growth and is detected when a child progresses through puberty. Even in genetically affected family members, a child that carries the muted gene from birth may appear

A diagnosis at a young age usually, but not always, signifies a serious heart condition that requires aggressive treatment. The concern lies in the uncertainty of how the heart muscle will respond with each additional growth spurt. With some older children, the condition may stabilize over time with the aid of certain medications or surgery. In severe cases, small children may experience progressive symptoms quickly leading to heart failure. This presentation contrasts with most diagnosed adults who may only have minor symptoms without serious limitations or major problems for years.Aside from differences in the cause and manifestation, cardiomyopathy may also progress differently in children than adults. When children are diagnosed at an early age, the prognosis may be poor depending on the form of cardiomyop‐ athy and the stage of the disease. For example, dilated cardiomyopathy can progress quite rapidly when diagnosed in young children. Up to 40% of diagnosed children with dilated cardiomyopathy fail medical management within the first year of diagnosis and of those that survive many have permanently impaired heart function. Children diagnosed with hypertro‐ phic cardiomyopathy seem to fare better but the outcome is highly variable.Mortality and heart transplant rates of childhood cardiomyopathies are much higher than in adults due to the
