Hypoplastic left heart syndrome overview

# Overview
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 congenital heart defect; 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.
Hypoplastic left heart syndrome is a rare congenital heart defect in which the left side of the heart is severely underdeveloped. In babies with HLHS, the aorta and left ventricle are very small, and the aortic and mitral valves are either too small to allow sufficient blood flow or are atretic (closed) altogether.  As blood returns from the lungs to the left atrium, it must pass through an atrial septal defect to the right side of the heart.             

# Pathophysiology
In patients with hypoplastic left heart syndrome, the left side of the heart is unable to send enough blood to the body. As a result, the right side of the heart must maintain the circulation for both the lungs and the body. The right ventricle can support the circulation to both the lungs and the body for a while, but this extra workload eventually causes the right side of the heart to fail.

# Causes
As with most congenital heart defects, there is no known cause. Approximately 10% of patients with hypoplastic left heart syndrome also have other birth defects.

# Differentiating Hypoplastic left heart syndrome from other Diseases
Signs and symptoms of hypoplastic left heart syndrome may be similar to other conditions. A differential diagnosis is essential to definitively diagnose hypoplastic left heart syndrome from associated conditions.

# Risk Factors
Hypoplastic left heart is more common in males than in females.

# Natural History, Complications and Prognosis
Failure to treat hypoplastic left heart syndrome can be fatal for the infant. However, with treatment, infants have a good chance at survival well into late adulthood. Potential complications may develop such as heart failure, arrhythmias, and even neurological complications.

# Diagnosis

## History and Symptoms
At first, a newborn with hypoplastic left heart may appear normal. Symptoms usually occur in the first few hours of life, although it may take up to a few days to develop symptoms. Common symptoms include cyanosis, dyspnea, and poor circulation.

## Physical Examination
A physical examination is an integral part of diagnosing hypoplastic left heart syndrome. During a routine visit, a doctor may find signs of right ventricle enlargement, presence of additional birth defects, and hemodynamic imbalances.

## Laboratory Findings
Laboratory studies that should be ordered include a complete blood count, and an arterial blood gas.

## Electocardiogram
An electrocardiogram should be ordered if hypoplastic left heart syndrome is suspected. Findings that may be depicted are right axis deviation, right ventricular hypertrophy, and prominent p waves.

## Chest X Ray
Findings on chest x ray include increased markings of pulmonary vasculature, and cardiomegaly.

## Echocardiography
The echocardiogram is of high diagnostic value in the assessment of hypoplastic left heart syndrome. Doppler echocardiography will also help in visualizing the flow in the ventricles.

# Treatment

## Medical Therapy
Failure to treat hypoplastic left heart syndrome can be fatal for the infant. Medical therapy can be used prior to surgical intervention to allow the ductus to open and promote bloodflow. It is only a temporary solution, surgical intervention is needed to ultimately repair hypoplastic left heart syndrome.

## Surgery
Failure to treat hypoplastic left heart syndrome can be fatal for the infant. Surgical therapy is the only true way to treat and permanently fix hypoplastic left heart syndrome. Two main methods exist for treatment: transplantation and a three-stage surgical procedure.