Congenital heart defect

A congenital heart defect (CHD) is a defect in the structure of the heart and great vessels of a newborn. Most heart defects either obstruct blood flow in the heart or vessels near it or cause blood to flow through the heart in an abnormal pattern, although other defects affecting heart rhythm (such as long QT syndrome) can also occur. Heart defects are among the most common birth defects and are the leading cause of birth defect-related deaths.

Overview

A congenital heart defect is one that develops in the womb and is present at birth. After birth, congenital heart defects can be broadly categorised into two groups: acyanotic heart defects ("pink" babies) and cyanotic heart defects ("blue" babies).

Epidemiology

( Affecting approximately one in every 125 babies born, congenital heart defects are the most common birth defect (March of Dimes). Forty thousand people are born each year with a CHD; 4,000 will not survive their first year(The Children's Heart Foundation). Twice as many children die each year from a CHD than all forms of Pediatric Cancers combined (The Children's Heart Foundation). The eight most common defects account for 80% of all congenital heart diseases, while the remaining 20% consist of many independently infrequent conditions or combinations of several defects. Ventricular septal defect (VSD) is generally considered to be the most common type of malformation, accounting for about 1/3 of all congenital heart defects.

The incidence is higher when a parent or a sibling has a heart defect (4–5%), in stillborns (3–4%), abortuses (10–25%), and premature infants (2%).

The number of adults with problems connected to a congenital heart defect is rising, passing the number of children with congenital heart defects in most Western countries. This group is referred to as grown-up congenital heart disease (GUCH) patients.

Etiology

The cause of most congenital heart defects is unknown.

Where a cause is known, it may be of a multifactorial origin and/or a result of genetic predisposition and environmental factors.

Known genetic causes of heart disease includes chromosomal abnormalities such as trisomies 21, 13, and 18, as well as a range of newly recognised genetic point mutations, point deletions and other genetic abnormalities as seen in syndromes such as Velo-Cardio-Facial Syndrome , familial ASD with heart block, Alagille syndrome, Noonan syndrome, and many more.

Known antenatal environmental factors include maternal infections (Rubella), drugs (alcohol, hydantoin, lithium and thalidomide) and maternal illness (diabetes mellitus, phenylketonuria, and systemic lupus erythematosus).

Relation of congenital heart defects with sex

Some congenital heart diseases occur more frequently in males, whereas other ones in females. The most well defined "female’s" defects are patent ductus arteriosus (1♂♂ : 2.72♀♀), Lutembacher disease (1♂♂ : 2.1♀♀), and ostium secundum (1♂♂ : 1.84♀♀) (Table) (analysis based on about 32 000 cases of congenital failures of heart and large vessels). The arterial channel makes an integral part of blood circulation of late stages of development of a fetus and normally gets closed during the first year after birth. The oval window, is the second channel connecting the big and small circles of blood circulation of a fetus. If closing of an arterial channel and an oval window does not occur, the appropriate formations are considered as defects. These formations as necessary attributes of a structure of adult normal cardiovascular system can be found at representatives of the lowest (down to reptiles inclusive) classes of vertebrata.

Sex ratio of patients with congenital heart defects

Congenital heart defect	Sex ratio, males:females
Patent ductus arteriosus	1 : 2.72
Lutembaher disease	1 : 2.14
Ostium secundum	1 : 1.84
Ventricular septal defect and patent ductus arteriosus	1 : 1.51
Fallot's triad	1 : 1.45
Eisenmenger's complex	1 : 1.40
Partial atrioventricular canal	1 : 1.36
Ostium primum	1 : 1.20
Partial anomalous pulmonary venous connection	1 : 1.19
Ventricular septal defect	1 : 1.02
Aortopulmonary window	1 : 1.01
Atrioventricular canal	1 : 1.01
Ebstein's anomaly	1.02 : 1
Stenosis of lung artery	1.04 : 1
Tricuspid atresia	1.16 : 1
Truncus arteriosus	1.21 : 1
Tetralogy of Fallot	1.35 : 1
Coarctation of aorta and an open arterial channel	1.37 : 1
Total anomalous pulmonary venous connection	1.39 : 1
Transposition of the great arteries	1.90 : 1
Coarctation of the aorta	2.14 : 1
Aortic stenosis	2.66 : 1

Most well-defined "male" congenital heart defects are: aortic stenosis (2.66♂ : 1♀), coarctation of the aorta (2.14♂ : 1♀), transpositions of the great arteries (1.90♂ : 1♀), a total anomalous pulmonary venous connection (1.39♂ : 1♀), and coarctation of aorta with an open arterial channel (1.37♂ : 1♀).

Other congenital heart defects are of a "neutral" type. The frequency of occurrence is about the same for both sexes. Among them it is possible to allocate simple (Aortopulmonary window and ostium primum) and complex (partial and full atrioventricular canal, Ebstain's anomaly and tricuspid atresia) defects. Simple defects of this group, as well as female defects, can be considered atavistic. The difference between them is that these defects, contrary to female ones, represent a return to the far past in the onthogenetic and phylogenetic sense. They can be considered as a consequence of a block in heart development at early stages of embriogenesis (the first 2-3 months of the embryo's life during which the anatomic formation of the heart occurs), and at earlier (in comparison to female defects) stages of phylogenesis. For complex defects of the neutral group, the sex ratio depends on which of their components prevail—female or male.

Theories

Rokitansky (1875) explained congenital heart defects as breaks in heart development at various ontogenesis stages. Spitzer (1923) treats them as returns to one of the phylogenesis stages. Krimsky (1963), synthesizing two previous points of view, considered congenital heart diseases as a stop of development at the certain stage of ontogenesis, corresponding to this or that stage of the phylogenesis. Hence these theories can explain feminine and neutral types of defects only.

According to “Teratological rule of sexual dimorphism” (V. Geodakian, 1970) inborn anomalies that have atavistic nature appear more frequently among the females, and futuristic anomalies appear among males. This rule was applied to explain differences in sex ratio observed for congenital heart defects. Indeed, no one of male’s components of congenital heart defects have a corresponding similar formation at normal embryo or at phylogenetic predecessors of the humans. Therefore they can be considered as unsuccessful tests of the evolution process.

Sex of the patient can be used as a diagnostic symptom. This symptom is stable, cheap and does not harm the patient compare to some invasive diagnostic procedures.

Major categories

Patent ductus arteriosus

The ductus arteriosus is a temporary pathway in the foetal heart between the pulmonary artery and aorta, which allows blood to bypass the fetus's nonfunctioning lungs until birth. Normally, the ductus closes within a few hours or days of birth; when it does not, the result is patent ductus arteriosus. This defect is common in premature infants but rare in full-term infants.

Hypoplasia

Hypoplasia can affect the heart, which typically results in the failure of either the right ventricle or the left ventricle to develop adequately, leaving only one side of the heart capable of pumping blood to the body and lungs. Hypoplasia of the heart is rare but is the most serious form of CHD; it is called hypoplastic left heart syndrome when it affects the left side of the heart and hypoplastic right heart syndrome when it affects the right side of the heart. In both conditions, the presence of a patent ductus arteriosus (and, when hypoplasia affects the right side of the heart, a patent foramen ovale) is vital to the infant's ability to survive until emergency heart surgery can be performed, since without these pathways blood cannot circulate to the body (or lungs, depending on which side of the heart is defective). Hypoplasia of the heart is generally a cyanotic heart defect.

Obstruction defects

Obstruction defects occur when heart valves, arteries, or veins are abnormally narrow or blocked. Common obstruction defects include pulmonary valve stenosis, aortic valve stenosis, and coarctation of the aorta, with other types such as bicuspid aortic valve stenosis and subaortic stenosis being comparatively rare. Any narrowing or blockage can cause heart enlargement or hypertension.

Septal defects

The septum is a wall of tissue which separates the left heart from the right heart. It is comparatively common for defects to exist in the interatrial septum or the interventricular septum, allowing blood to flow from the left side of the heart to the right, reducing the heart's efficiency. Ventricular septal defects are collectively the most common type of CHD, although approximately 30% of adults have a type of atrial septal defect called patent foramen ovale. Septal defects may or may not cause cyanosis depending on the severity of the defect.

Cyanotic defects

Cyanotic heart defects are called such because they result in cyanosis, a bluish-grey discoloration of the skin due to a lack of oxygen in the body. Such defects include persistent truncus arteriosus, total anomalous pulmonary venous connection, tetralogy of Fallot, transposition of the great vessels, and tricuspid atresia.

Other defects

• Ebstein's anomaly
  
• Brugada syndrome
• Marfan syndrome
• DiGeorge Syndrome

Signs and Symptoms

Symptoms and signs are related to the type and severity of the heart defect. Some children have no signs while others may exhibit shortness of breath, cyanosis, chest pain, syncope, sweating, heart murmur, respiratory infections, underdeveloping of limbs and muscles, poor feeding, or poor growth. Most defects cause a whispering sound, or murmur, as blood moves through the heart causing some of these symptoms. All of these symptoms occur at a young age of a child or infant and are typically found during a physical examination.

Treatment

Sometimes CHD improves with no treatment necessary. At other times the defect is so small and does not require any treatment. Most of the time CHD is serious and requires surgery and/or medications. Medications include diuretics, which aid the baby in eliminating water, salts, and digoxin and in strengthening the contraction of the heart. This slows the heartbeat and removes some fluid from tissues. Some defects require surgical procedures to repair as much as possible to restore circulation back to normal. In some cases, multiple surgeries are needed to be performed to help balance the circulation. Interventional cardiology now offers patients minimally invasive alternatives to surgery. Device closures can now be treated with a standard transcatheter procedure using a closure device mounted on a balloon catheter.

Defects

• Aortic stenosis
• Atrial septal defect (ASD)
• Atrioventricular septal defect (AVSD)
• Cardiomyopathy
• Coarctation of the aorta (CoA)
• Dextrocardia
  
• Ebstein's anomaly
• Hypoplastic left heart syndrome (HLHS)
• Interrupted aortic arch (IAA)
• levo-Transposition of the great arteries (l-TGA)
• Partial anomalous pulmonary venous connection (PAPVC)
• Patent ductus arteriosus (PDA)
• Pulmonary atresia
  
• Pulmonary stenosis
• Tetralogy of Fallot (ToF)
• Total anomalous pulmonary venous connection (TAPVC)
• dextro-Transposition of the great arteries (d-TGA)
• Tricuspid atresia
  
• Truncus arteriosus
• Ventricular septal defect (VSD)
• Bicuspid aortic valve
• Mitral Stenosis