While the normal heart has two ventricles, in some birth defects, one of these ventricles may be absent or poorly developed. This condition is called single ventricle or univentricular heart. This can include such problems as tricuspid valve atresia, hypoplastic left-heart syndrome, hypoplastic right-heart syndrome (pulmonary atresia with intact ventricular septum), mitral valve atresia, and double-inlet ventricle. Other types of heart defects, such as atrioventricular canal defects or double outlet right ventricle, may be complicated by an underdeveloped ventricle. The ventricular structure may resemble the normal left ventricle or the normal right ventricle. Sometimes it resembles neither, and this is called indeterminate ventricle morphology. Single-ventricle defects are among the most complex congenital heart problems known
In a single ventricle heart, there are two normal atria. These open into the ventricle through an atrio-ventricular (AV) valve. There might be two AV valves, both opening into the ventricle - a condition called Double Inlet Ventricle, or there may be one AV valve only, the other one being absent (atretic). The single ventricle connects with the aorta and pulmonary artery. These two great arteries may be normal or interchanged in position. Some patients have obstruction of the great arteries - pulmonary stenosis and sub-aortic stenosis.
The main problem with a single ventricle is the mixing of blood inside the ventricular chamber. Unoxygenated blood from the veins enters the right atrium and from there reaches the single ventricle. Oxygenated blood returning from the lungs flows into the left atrium and into the single ventricle. Inside the ventricle, both mix together. From here, the mixed blood flows into the aorta and pulmonary artery.
Patients with single-ventricle defects often need multiple operations. These include shunts such as Blalock-Taussig (B-T) or Glenn, placing a band on the pulmonary artery, or the Fontan operation. The Fontan operation largely separates the heart into two circulations. This lets oxygen-poor blood go to the lungs and oxygen-rich blood go to the body. The Fontan operation substantially reduces the mixing of blue and red blood and produces a normal or near-normal oxygen supply to the body. It also reduces the risk of a stroke or other complications, and decreases the workload on the single ventricle. A Fontan operation can't be done if you have pulmonary hypertension (high blood pressure in the lungs).
In a single ventricle heart, there are two normal atria. These open into the ventricle through an atrio-ventricular (AV) valve. There might be two AV valves, both opening into the ventricle - a condition called Double Inlet Ventricle, or there may be one AV valve only, the other one being absent (atretic). The single ventricle connects with the aorta and pulmonary artery. These two great arteries may be normal or interchanged in position. Some patients have obstruction of the great arteries - pulmonary stenosis and sub-aortic stenosis.
The main problem with a single ventricle is the mixing of blood inside the ventricular chamber. Unoxygenated blood from the veins enters the right atrium and from there reaches the single ventricle. Oxygenated blood returning from the lungs flows into the left atrium and into the single ventricle. Inside the ventricle, both mix together. From here, the mixed blood flows into the aorta and pulmonary artery.
Patients with single-ventricle defects often need multiple operations. These include shunts such as Blalock-Taussig (B-T) or Glenn, placing a band on the pulmonary artery, or the Fontan operation. The Fontan operation largely separates the heart into two circulations. This lets oxygen-poor blood go to the lungs and oxygen-rich blood go to the body. The Fontan operation substantially reduces the mixing of blue and red blood and produces a normal or near-normal oxygen supply to the body. It also reduces the risk of a stroke or other complications, and decreases the workload on the single ventricle. A Fontan operation can't be done if you have pulmonary hypertension (high blood pressure in the lungs).