Double inlet left ventricle (DILV) is a rare condition and its exact etiology is currently unknown. It occurs in 5 to 10 out of 100 000 births. It is suspected to be due to abnormal development of the heart tube during intrauterine life and it leads to the mal-development of heart valves and chambers. As a result, only one heart chamber is actively involved in pumping of blood.
In many cases DILV is associated with other congenital heart anomalies such as:
- Coarctation of the aorta, or narrowing of a part of the aorta
- Pulmonary atresia or failure of the pulmonary valve to develop properly - the pulmonary valve guards the blood flow from the right ventricle into the pulmonary trunk in the normal heart
- Pulmonary stenosis, which leads to a smaller-than-usual pulmonary trunk flow
The abnormal structure in DILV
In DILV, only one ventricle is well-formed, usually the left. Therefore, patients with DILV often have a large left ventricle and a markedly smaller, hypoplastic or incompletely formed right ventricle. The left ventricle is the heart chamber that pumps blood to the body to supply the needs of all tissues and cells in the body. The right ventricle is the chamber that pumps blood to the lungs to renew its oxygen content.
In DILV, the left ventricle receives all the venous blood from the body, which is also called a univentricular atrioventricular connection. Thus it mixes deoxygenated blood from the great veins, namely the superior and inferior vena cavae, with the oxygenated blood from the lungs via the pulmonary veins. The blood pumped to the systemic circulation is thus a mixture of incompletely oxygenated blood, leading to poor oxygen supply to the cells of the body.
In addition to these two abnormalities, the heart may have a hole between the two ventricles (a ventricular septal defect, VSD).
DILV may also be caused by transposition of the great vessels, so that the aorta and the pulmonary trunk arise from the right and the left ventricles respectively, instead of their normal positions. In other children, DILV is caused by the presence of a ventricular septal defect in which both lower chambers, or ventricles, are connected by an abnormal opening in the septum between them.
Patients with DILV may develop pulmonary vascular disease. This is because of the excessive amount of blood being pumped from the left ventricle.
The symptoms of DILV depend on whether the condition is isolated or associated with other anomalies. They may range from minor to serious, and are caused by too much blood being pumped to the lungs, or by the pumping of poorly oxygenated blood to the body. Common manifestations include:
- Inability to feed properly due to tiring quickly
- Poor feeding
- Cyanosis, or a bluish-gray tinge of the lips and around the mouth, caused by the presence of reduced hemoglobin in both arterial and venous blood.
- Failure to thrive and gain weight
- Pallor of the skin
- Swelling or edema of the legs and the abdomen
- Breathing problems due to lack of oxygen or excessive pulmonary blood flow, such as breathlessness