| From your Guide Dr.MANI |  | |
Single Ventricle | ||
| From your Guide Dr.MANI | | |
Single Ventricle | ||
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What is the heart defect called Single Ventricle ?
What happens in Single Ventricle ?
Should Single Ventricle be treated ? Read on ...
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. 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.
In a single ventricle heart, there are two normal atria - right and left. 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
one AV valve only, the other one being absent (atresia)
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 functional disturbance in single ventricle is the mixing of blood inside the ventricular chamber. Impure blood from the veins enters the right atrium and from there reaches the single ventricle. Pure 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.
The clinical picture depends on the relative amount of the total blood flow that reaches the lungs. Three scenarios are possible:
1. The pulmonary artery may be normal, with no obstruction. Because the lung blood vessels are thin walled, they offer lower resistance to the flow of blood than the aorta and its branches. So a larger proportion of blood from the single ventricle will flow into the pulmonary artery and into the lungs. In many ways, this situation is similar to a very large VSD. This increased volume of blood returns back to the ventricle and is once again pumped out, resulting in a high workload on the single ventricle. Soon, unable to tolerate this stress, the ventricle fails.
2. The pulmonary artery may be obstructed (stenosis). This increases the resistance to blood flow into the lungs. A larger proportion of blood from the single ventricle will flow into the aorta and its branches. The amount of blood flowing into the lungs for purification and addition of oxygen is thus reduced. So blood returning to the single ventricle from the veins is more impure and contains less oxygen. This causes oxygen content in blood leaving the ventricle into the aorta also to be reduced, producing a bluish discoloration called cyanosis.
3. The pulmonary artery may be mildly narrowed. The resistance in both the pulmonary artery and aorta are nearly the same in this condition. As a result, blood from the single ventricle will flow in almost equal proportion into both the great arteries. This situation is called a "balanced circulation", and may not produce any clinical symptoms for a long time.
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