Hypoplastic Left Heart Syndrome - Causes, Symptoms, Diagnosis, and Treatment

Introduction

Hypoplastic left heart syndrome, or HLHS, is a cardiovascular defect present during birth. This defect hampers the regular functioning of the heart. As the fetus develops, the left portion of the heart does not grow correctly. Hypoplastic left heart syndrome can be understood as a congenital heart defect. This congenital heart defect is considered to be a highly critical condition because the newborn needs to have surgery immediately after birth.

Hypoplastic left heart syndrome comes under the category of a critical congenital heart defect. When the fetus develops inside the mother’s womb, the right side of the heart pumps deoxygenated blood from the heart to the lungs, and the left side transfers oxygenated blood to the rest of the body. There are two openings present in the heart of the fetus that close immediately after birth- patent foramen ovale and patent ductus arteriosus. In babies with hypoplastic left heart syndrome, the oxygenated blood fails to reach the body since the left side of the heart is not well developed. The blood supply to the rest of the body thus becomes extremely difficult.

Whereas, hypoplastic right heart syndrome is a group of congenital cardiac anomalies affecting the right side of the heart. This condition involves the underdeveloped or absence of a tricuspid valve, as well as poorly developed or absent right ventricle and pulmonary valve. The right side of the heart cannot pump enough blood to the lungs when the structures are too small or malfunction. An infant with untreated HRHS will have erratically low oxygen levels as a result.

What Are the Structures That Are Affected By Hypoplastic Left Heart Syndrome?

The heart is divided into four chambers: the upper left and right atrium and the lower left and right ventricles. Hypoplastic left heart syndrome hampers the structure and function of several structures on the left portion of the heart. This leads to these particular areas not developing completely. Mentioned below are the structures that get affected due to hypoplastic left heart syndrome.

• The left ventricle is too small.

• The mitral valves are not formed.

• The aortic valve is very small.

• The ascending portion of the aorta is not developed.

• Atrial septal defect.

What Are the Causes of Hypoplastic Left Heart Syndrome?

Hypoplastic left heart syndrome does not have any established cause for its prevalence. Nevertheless, there are some factors that have been studied to pose the risk of developing hypoplastic left heart syndrome, such as those mentioned below. It should be noted that hypoplastic left heart syndrome is diagnosed as soon as the baby is born. It is also possible to diagnose the defect during pregnancy.

• Genetic variation and defects.

• Chromosome alterations.

• Allergic food, taken during pregnancy.

• Presence of another congenital heart defect.

What Are the Signs and Symptoms of Hypoplastic Left Heart Syndrome?

Generally, babies with hypoplastic left heart syndrome undergo correction and rehabilitation immediately after birth. During this, certain clinical manifestations confirm the diagnosis of hypoplastic left heart syndrome.

Mentioned below are some signs and symptoms of hypoplastic left heart syndrome.

• Difficulty in breathing.

• Pounding heartbeat.

• Feeble pulse.

• Bluish discoloration of the skin.

• Whooshing murmurs in the heart.

• Low levels of oxygen.

• Electrocardiograph showing an unusual pattern.

• Poor feeding.

• Clammy and cool skin.

How Is Hypoplastic Left Heart Syndrome Diagnosed?

Hypoplastic left heart syndrome can be diagnosed during pregnancy or even after birth. Mentioned below are a few of the diagnostic tools that help in the diagnosis of hypoplastic left heart syndrome.

• Pulse Oximetry Screening: This indicates the level of oxygen in an infant's blood.

• Echocardiography: After birth or throughout pregnancy, echocardiography can identify HLHS. During prenatal life, the pathophysiology of HLHS is evolving. As pregnancy continues, the left ventricle will get smaller, and an echocardiogram may not show the abnormality until the third trimester.

• Chest X-rays: This displays the infant's heart and lungs' dimensions and form.

• Prenatal testing.

• Presence of family defects.

• Blood Testing: Evaluations of acid-base status, oxygenation and ventilation, renal function, and hematocrit should be conducted using blood work that includes arterial blood gas, complete blood count, electrolytes, and lactate.

• Genetic Testing: Additionally, as HLHS has been linked to several chromosomal disorders, including Turner, DiGeorge, and Down syndrome, genetic testing ought to be done. Chromosome abnormalities in newborns are associated with increased rates of morbidity and mortality, as well as prolonged hospital stays following surgery.

How to Treat Hypoplastic Left Heart Syndrome?

Hypoplastic left heart syndrome has several treatment modalities. The healthcare provider chooses the best treatment option according to the clinical manifestations of the patient. Mentioned below are a few of the treatment and management varieties for hypoplastic left heart syndrome.

• Medications to increase the strength of the cardiac muscles.

• Medications that aid in the removal of excess fluid from the body.

• High-calorie customized nutrition plan.

• Nutrition is given through a feeding tube.

• Norwood Operation: The Norwood surgical procedure is done during the initial two weeks by creating a new aorta and joining it to the right ventricle. Additionally, a tube is placed that supplies blood to the lungs via the right ventricle or the aorta. A combined technique is used occasionally. To preserve the connection between the pulmonary artery and the aorta, surgeons place a stent in the ductus arteriosus. Bands positioned around the pulmonary arteries narrow the blood supply to the lungs and open the heart's atria. A baby's skin will remain discolored following the Norwood treatment because the heart's blood still mixes oxygen-rich and oxygen-poor blood. The probability of a baby surviving can rise when they complete this round of treatment.

• Bidirectional Glenn Shunt Procedure: The Bi-directional Glenn Shunt procedure is done when the patient is approximately six months old by creating a strong and direct link between the superior vena cava and the pulmonary artery.

• Fontan Procedure: When a child is between the ages of 18 months and four years, this procedure is typically performed. By making an opening in the inferior vena cava, one of the blood channels that returns blood to the heart, the surgeon allows oxygen-poor blood to enter the pulmonary arteries directly. The blood is subsequently sent into the lungs by the pulmonary arteries. The Fontan operation allows the remaining oxygen-depleted blood from the body's tissues to move to the lungs. There is minimal mixing of oxygen-poor and oxygen-rich blood in the heart following this operation. Consequently, the skin will not appear discolored.

• Heart Transplant: Heart transplantation is an additional surgical option. However, this method is not employed as frequently because the quantity of available hearts for transplantation is constrained. For the rest of their lives, children who received heart transplants must take medication to keep the donor's heart from being rejected.

It should be noted that children who undergo surgical correction can not be permanently cured. They may have lifelong complications and may also require regular follow-ups with the cardiologist in order to assess their progress.

What Are the Long-Term Consequences of Hypoplastic Left Heart Syndrome?

Children with hypoplastic left heart syndrome typically pass away in their early infancy if they are not treated. Throughout their first year of life, 20 % to 60 % of infants with hypoplastic left heart syndrome survive with treatment. Following that, approximately 40 % of the population survived over the ensuing five, ten, and 15 years. Healthy newborns do better than underweight babies when they are born at a regular weight and are not premature. Most infants who made it through their first year were still living at the age of 18, according to one study.

Conclusion:

Hypoplastic left heart syndrome is a congenital cardiovascular defect that hampers the heart and its structure and thus does not allow it to function to its best efficiency. The left ventricle is the section of the heart that gets affected the most. This leads to the heart not being able to differentiate between oxygen-rich and deoxygenated blood. Patients require immediate treatment. There are several surgical interventions, but none of them can promise a full recovery. Patients need to be examined and evaluated throughout their lives in case they have been diagnosed with hypoplastic left heart syndrome.