Heart Defects

• One of 120 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter or leave the heart.
• Before birth, a fetus uses oxygen obtained from the mother's blood through the placenta. The fetus does not breathe. Also, the path by which blood circulates through the heart and lungs is  different in fetus. After birth, a newborn must obtain oxygen using his own lungs.Therefore, many changes occur in the heart and blood vessels soon after birth.
• Before birth, blood that has not yet traveled to the lungs (venous blood) mixes with blood that has already traveled to the lungs (arterial blood). Such mixing occurs in the foramen ovale, a hole between the right and left atria and ductus arteriosus, a blood vessel connecting the pulmonary artery and the aorta. In the fetus, both venous and arterial blood contain oxygen, so mixing arterial and venous blood does not affect how much oxygen gets pumped to the body. After birth, arterial blood and venous blood do not normally mix. The foramen ovale and ductus arteriosus normally close within days to a couple of weeks after birth.
• Two general processes account for most of the symptoms resulting from heart defects. One is that blood flow gets altered or rerouted(shunting). Another is that not enough gets pumped to the body, usually because of a blockage.
• Shunting can cause oxygen-poor blood to mix with oxygen-rich blood that is pumped to the body tissues (right to left shunt). The more oxygen-poor blood that flows to the body, the more blue the body appears, particularly the skin and lips. Many heart defects are characterized by a bluish discoloration of the skin (cyanosis); cyanosis indicates that not enough oxygen-rich blood is reaching the tissues where it is needed.
• In heart failure, blood also backs up, often in the lungs. Heart failure can also develop when the heart pumps too weakly or when blood is blocked from flowing to the baby's body.
• Blockages may develop in the valves of the heart or in the blood vessels leading away from the heart. Blood may be impeded from flowing to the lungs because of narrowing of the pulmonary valve (pulmonary valves stenosis) or narrowing within the pulmonary artery itself (pulmonary valve stenosis). Blood may be impeded from flowing through the aorta to the body because of narrowing of the aortic valve (aortic valve stenosis) or blockage within the aorta itself (coarctation of the aorta).

Symptoms and Diagnosis

•  Often, heart defects produce few or no symptoms and are  not detectable even during a physical examination of the child. Some mild defects produce symptoms only later in life. 
• However, many heart defect do result in symptoms during childhood. 
• Because oxygen-rich blood is necessary for normal growth, development, and activity, infants and children with heart defects may fail to grow or gain weight normally. They may not be able to exercise fully.
• In more severe cases, cyanosis may develop, and breathing or eating may be difficult.
• Abnormal blood flow through the heart usually produce murmur sound that can be heard using a stethoscope; however, the vast majority of heart murmurs that occur during childhood are not caused by heart defects and are not indicative of any heart problems.
• Heart failure makes the heart beat rapidly and often causes fluid to collect in the lungs or liver.
• Many heart defects can be diagnosed before birth using ultrasound. After birth, heart defects are suspected when symptoms develop or when particular heart murmurs are heard.
• Diagnosing heart defects in children involves the same techniques used for diagnosing heart problems in adults. A doctor may be able to diagnose the defect after asking the family specific questions and performing a physical examination, ECG, and a chest x-ray. Ultrasound (echochardiography) is used to diagnose almost all of the specific defects. Cardiac catheterization often can show small abnormalities that are not detected with echocardiography or can further illuminate the details of the abnormality.

Treatment

      

Comparison of angioplasty and valvuloplasty

Images taken from http://www.know-heart-diseases.com and http://www.cardiosmart.org/

• Many significant heart defects are effectively corrected using open-heart surgery. When to perform the operation depends on the specific, its defect, its symptoms, and severity. For example, it may be better to postpone surgery until the child is a little older. However, severe symptoms resulting from a heart defects are most effectively relieved with immediate surgery.
• A narrowing can sometimes be relieved by passing a thin tube (catheter) through a blood vessel in the arm or leg into the narrowed area. A balloon attached to the catheter is inflated and widens the narrowing, usually in a valve (a procedure called balloon valvuloplasty) or blood vessel (a procedure known as balloon angioplasty). These balloon procedures spare the child from general anesthesia and open heart surgery. However, a balloon procedures are not usually as effective as surgery.
• If the aorta or pulmonary artery is severely blocked, a temporary shunt can sometime be created to keep an adequate amount of blood  flowing. A shunt can be created with a catheter balloon (for example, between the right and left atria - balloon septostomy).
• Drug prostaglandin E1 (alprostadil) can be given to keep the ductus arteriosus open, shunting blood between the aorta and pulmonary artery. 
• In rarer cases, when no other treatment helps, a heart transplant is performed, but the lack of donor hearts limits the availability of this procedue.
•  Most children who have significant heart defects are at increased risk for developing life-threatening bacterial infections of the heart and its valves (endocarditis). They need to take antibiotics before certain treatments and procedures.

Patent Ductus Arteriosus 

 Fetal echocardiogram of the ductus arteriosus (Courtesy of Drs. J. Moodley and Y. Shah)

Image taken from www.sahha.gov.mt/

•  In patent ductus arteriosus, the blood vessel connecting the pulmonary artery and the aorta (ductus arteriosus) fails to close as it usually does within the the first 2 weeks after birth.
• A left-to-right shunt causes extra blood flow, and pressure in the lungs may damage the lung tissue.
• Premature newborns are especially susceptible to patent ductus arteriosus and lung damage.
• Most often, the defect causes no symptoms. When symptoms do occur, they are usually difficulty breathing or cyanosis, which may be present at birth or not for several weeks after birth.
• When the infant has no symptoms, doctors most often suspect the defect when they hear a heart murmur.
• Use of indomethacin, a drug that inhibits the production of prostaglandins, closes the defect in 80% of infants. Indomethacin is most effective if given in the first 10 days after birth and is more effective in premature newborns that in full-term newborns. 
•  If the defect does not close after several doses of indomethacin, it is closed surgically.

Atrial and Ventricular Septal Defects

 

Image taken from www.nmtmedical.com/

• Atrial and ventricular septal defects are holes in the septum that separate the heart into left and right sides.
• Atrial septal defects are located between the atria while ventricular septal defects are located between the ventricles.
• These holes typically cause left-to-right shunting of blood. 
• Many atrial septal defects close by themselves, especially in the first year of life; many ventricular septal defects close within the first 2 years.
• Infants and most older children with atrial septal defects have no symptoms.
• In more severe case, children may develop heart murmurs, fatigue, and difficulty in breathing.
• The symptoms caused by atrial septal defects increase as the person ages. For example, heart failure may develop during middle age.
• Ventricular septal defects can vary from  small holes, which may cause a heart mumur but no symptoms and usually close by themselves, to larger holes that cause symptoms in infants.
• Significant ventricular septal defects usually cause more severe symptoms that atrial septal defects, because there is more shunting of blood.
• Because of the way lungs develop, shunting increases during the first 6 weeks after birth. Usually the murmur becomes louder, and symptoms, typically rapid breathing, sweating, and difficulty feeding, worsen.
• Mild symptoms of ventricular septal defect may be treated with diuretics (such as furosemide) or drugs that decrease resistance to the flow of blood to the body (such as captopril).
• If atrial and ventricular septal defects are large or cause symptoms, they are closed by surgery.