Hypoplastic left heart syndrome

Congenital heart defect

Hypoplastic left heart syndrome
Synonyms	Cyanotic heart disease – hypoplastic left heart
Pronounce
Field	Cardiology, Pediatric cardiology
Symptoms	Cyanosis, breathing difficulties, poor feeding, lethargy
Complications	Heart failure, developmental delays, multi-organ dysfunction
Onset	Congenital (present at birth)
Duration	Lifelong
Types
Causes	Abnormal cardiac development during pregnancy
Risks	Genetic factors, family history
Diagnosis	Prenatal ultrasound, echocardiography
Differential diagnosis	Other cyanotic heart defects (Tetralogy of Fallot, Transposition of the great arteries)
Prevention	Prenatal diagnosis, genetic counseling
Treatment	Surgical procedures (Norwood, Glenn, Fontan), heart transplantation
Medication	Prostaglandin E1, diuretics, inotropic agents
Prognosis	Variable; significant improvements with early intervention
Frequency	Approximately 2–3 per 10,000 live births
Deaths	High mortality rate without intervention; improved survival with surgery

Hypoplastic left heart syndrome (HLHS) is a rare congenital heart defect in which the left side of the heart is underdeveloped. This condition affects normal blood flow through the heart, as the left side of the heart is unable to effectively pump blood to the body.

Anatomy and Pathophysiology

In HLHS, several structures on the left side of the heart are affected, including the left ventricle, mitral valve, aortic valve, and aorta. The left ventricle is typically small and non-functional, the mitral and aortic valves may be stenotic or atretic, and the ascending aorta is often underdeveloped.

The underdevelopment of these structures leads to a reliance on the right ventricle to pump blood to both the lungs and the rest of the body. Blood flow to the body is dependent on a patent ductus arteriosus, a fetal blood vessel that connects the pulmonary artery to the aorta, which normally closes shortly after birth.

Clinical Presentation

Newborns with HLHS may appear normal at birth but can rapidly develop symptoms as the ductus arteriosus begins to close. Symptoms include:

• Cyanosis (bluish skin color)
• Rapid breathing
• Poor feeding
• Lethargy
• Cold extremities

Without intervention, HLHS is usually fatal within the first few days or weeks of life.

Diagnosis

HLHS can be diagnosed prenatally using fetal echocardiography. Postnatal diagnosis is typically confirmed with an echocardiogram, which can visualize the underdeveloped structures of the heart. Additional tests may include chest X-ray and electrocardiogram (ECG).

Treatment

Treatment for HLHS involves a series of surgeries or, in some cases, a heart transplant. The surgical approach, known as the Norwood procedure, is typically performed in three stages:

Stage 1: Norwood Procedure

This surgery is performed shortly after birth. It involves reconstructing the aorta and connecting it to the right ventricle, allowing the right ventricle to pump blood to the body.

Stage 2: Glenn Procedure

Performed at 4-6 months of age, this procedure connects the superior vena cava to the pulmonary arteries, reducing the workload on the right ventricle.

Stage 3: Fontan Procedure

This final surgery, performed at 18 months to 3 years of age, connects the inferior vena cava to the pulmonary arteries, completing the separation of oxygenated and deoxygenated blood.

Prognosis

The prognosis for children with HLHS has improved significantly with advances in surgical techniques. However, these children require lifelong follow-up with a cardiologist and may face complications such as arrhythmias, heart failure, and the need for additional surgeries.

Related pages

• Congenital heart defect
• Echocardiography
• Heart transplant