Babies born with hypoplastic left heart syndrome often appear to be normal at birth. The signs and symptoms begin to show effect after the first few hours. The following are the signs and symptoms of this congenital condition:

• Cyanosis characterized by grayish to bluish skin color
• Lethargy
• Decreased pulse rate
• Shortness of breath
• Rapid breathing
• Extremities are cold
• Poor sucking and feeding
• Pounding heart
• Dilated pupils

An ultrasound examination during the second trimester of pregnancy can reveal presence of hypoplastic left heart syndrome [6]. This imaging modality can be enhanced by the use of color Doppler studies [7]. After birth, a thorough physical examination would reveal heart failure. In case of heart failure the following signs would be evident:

• Rapid breathing
• Liver enlargement
• Lethargy 
• Fast heart rate
• Heart murmur
• Abnormal heart sounds and
• Weak pulse at locations of wrist and groin regions

In addition to physical examination, other tests such as cardiac catheterization, echocardiogram, ECG and x-ray of the chest would be done. An echocardiogram reveals small underdeveloped left ventricle and aorta. This test is also used for tracking the blood flow and can also help detect other associated heart defects if present.

Treatment of hypoplastic left heart syndrome is usually done through a 3 step surgical procedure. Before the surgery, the condition is managed through medications that help dilate the blood vessels and keep the ductus arteriosus open. The baby may be required to put on ventilator if she experiences breathing problems. Following this, surgery is carried out in the following 3 steps:

• The Norwood operation involves reconstruction of the aorta and connecting it to the lower right chamber of the heart [8]. After the operation is successfully completed, the chances of survival increase. Nasogastric feeding for infants may be required after this procedure to increase calorie breast milk or formula [9].
• A hemi–Fontan procedure is done between 4 to 12 months of age. This procedure reduces the work of the right ventricle making it to pump blood only to the aorta. 
• The Fontan procedure is carried out between 18 months and 3 years of age. After this surgery, there is no mixing of oxygen rich and oxygen poor blood [10]. 

If hypoplastic left heart syndrome is not treated on time it can turn fatal. Surgery remains the primary mode of treatment and survival rates are as high as 75% after the first procedure. Prognosis gets better after success of every surgical procedure. The child’s recovery is also largely dependent on the size and functioning of the right ventricle.

Complications

When hypoplastic left heart syndrome is left untreated, it can pose the following complications:

• Arrhythmias characterized by irregular and fast heart beats
• Heart failure
• Chronic diarrhea due to protein losing enteropathy
• Ascites characterized by accumulation of fluid in the abdomen
• Complications of the nervous system
• Blockage of the artificial shunt
• Sudden death

The exact cause behind the development of hypoplastic left heart syndrome is unknown. Such a condition develops during fetal development where the structures of the left side of the heart does not properly form. Hypoplastic left heart syndrome is thought to run in families; this means that siblings of the affected child are at an increased risk of developing it.

According to the Centers for Disease Control and Prevention, each year about 960 babies in the US are diagnosed with hypoplastic left heart syndrome. This means that about 16 to 36 cases in every 10,000 babies in US are born with this condition [2].

Hypoplastic left heart syndrome represents 1.2 -1.6% of all congenital heart diseases in the United States [3]. Before heart repair surgery was available this congenital anomaly claims 25% of all cardiac neonatal deaths in the country [4].

In condition of hypoplastic left heart syndrome, the heart is unable to supply blood to the rest of the body due to malformation of the left ventricle. In addition to this, the valves in the left side of the heart do not work properly [5]. Also, the aorta is smaller than normal. All these sequence of events give rise to the condition of hypoplastic left heart syndrome.

During the first few days after birth, the heart pumps blood to lungs and rest of the body through a natural opening referred to as foramen ovale. This opening however closes after few days and then the heart is unable to pump blood giving rise to life threatening conditions.

Since this is a congenital defect its development cannot be prevented. But diagnosis of the condition during pregnancy can be done and appropriate decision taken. In such cases, it is advised that the delivery be done in hospital that have proper pediatric cardiac care unit.

Hypoplastic left heart syndrome is a congenital defect wherein the left side of the heart does not develop properly [1]. The left portion of the heart consists of mitral valve, aortic valve, left ventricle, aorta and atrium. These structures either do not develop properly or are too small in size.

Hypoplastic left heart syndrome is a rare heart defect that takes place during fetal development. This condition is more common with males. It has been seen that babies born with hypoplastic left heart syndrome often seem to suffer from atrial septal defect as well.

Definition

Hypoplastic left heart syndrome is defined as the condition wherein the left portion of the heart fails to develop appropriately. It is a congenital condition that poses life threatening consequences for the new born baby.

Cause

The cause behind development of such a heart abnormality is yet to be known. In this condition, the left side of the heart that consists of the mitral valve, aorta, aortic valve and left ventricle do not develop normally. It has been estimated that about 10% of babies born with hypoplastic left heart syndrome are also known to suffer from other heart defects too. 

Symptoms

Symptoms of hypoplastic left heart syndrome include cyanosis, rapid heart rate, arrhythmias, lethargy, poor pulse rate, poor sucking, and shortness of breath and cold extremities. 

Diagnosis

The condition can be diagnosed through an ultrasound examination during the second trimester. After birth, the appearance of physical signs is an indication of hypoplastic left heart syndrome. In addition, echocardiogram, ECG, cardiac catheterization and x-ray of the chest confirms diagnosis.

Treatment

Treatment is primarily initiated with medications and the baby may also be put on ventilator if required. Following this, 3 step surgical procedures are done to correct the heart abnormalities.

1. Noonan JA, Nadas AS. The hypoplastic left heart syndrome. Pediat Clinics N Amer. 1958; 5:1029
2. Fyler DC. Report of the New England Regional Infant Cardiac Program. Pediatrics. Feb 1980; 65(2 Pt 2):375-461.
3. Freedom RM. Aortic atresia. In: Keith JD, Rowe RD, Vlad P, eds. Heart Disease in Infants and Children. 3rded. New York: McMillian; 1978.
4. Norwood WI Jr. Hypoplastic left heart syndrome. Ann Thorac Surg. Sep 1991; 52(3):688-95.
5. Rao PS, Striepe V, Merrill WH. Hypoplastic left heart syndrome. In: Kambam J (Ed.). Cardiac Anesthesia for Infants and Children. St. Louis, MO: Mosby-Year Book; 1994:296-309.
6. Galindo A, Nieto O, Villagra S, Graneras A, Herraiz I, Mendoza A. Hypoplastic left heart syndrome diagnosed in fetal life: associated findings, pregnancy outcome and results of palliative surgery. Ultrasound Obstet Gynecol. May 2009; 33(5):560-6.
7. Norwood WI, Lang P, Hansen DD. Physiologic repair of aortic atresia-hypoplastic left heart syndrome. N Engl J Med. Jan 6 1983; 308(1):23-6.
8. Norwood WI, Kirklin JK, Sanders SP. Hypoplastic left heart syndrome: experience with palliative surgery. Am J Cardiol. Jan 1980; 45(1):87-91.
9. Braudis NJ, Curley MA, Beaupre K, et al. Enteral feeding algorithm for infants with hypoplastic left heart syndrome poststage I palliation. Pediatr Crit Care Med. Jul 2009; 10(4):460-6.
10. Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax. May 1971; 26(3):240-8.