Congenital Heart Disorders – Disorders with Mixed Blood Flow
Disorders with Mixed Blood Flow
Mixing of the blood from the pulmonary and systemic circulation in the chambers of the heart results in a relative deoxygenation of the blood flowing. The defects under this include transposition of the great arteries, total anomalous pulmonary venous return, truncus arteriosus and hypoplastic left heart syndrome.
Normally, the pulmonary artery arises from the right ventricle and the aorta from the left ventricle. With transposition of the great arteries, the pulmonary artery arises from the left ventricle while the aorta from the right ventricle. As blood (unoxygenated) enters the right atrium it flows to the right ventricle. Because the aorta is connected to the right ventricular portion of the heart completely deoxygenated blood goes out into the aorta to the different parts of the body. On the other side of the heart oxygenated blood enters the left atrium via the pulmonary veins. It flows to the left ventricle then back to the pulmonary artery then to the lungs and returns to the left atrium. Two closed circulatory systems are present. In most cases, ASD and VSD are present with transposition of the great arteries. This makes the entire heart have a single yet mixed circulation.
- Cyanosis at birth
- There may be murmur or there may be various murmurs (depending on the shunting of blood through atrial or ventricular septal defects)
Normally, the pulmonary vein drains oxygenated blood to the left atrium. In total anomalous pulmonary venous return, the pulmonary veins drain the blood to the right atrium or the superior vena cava. Blood from the right atrium enters the right ventricle to the pulmonary artery, lungs, pulmonary veins and back to the right atrium. Often, an absent spleen is associated with this disorder.
Normally aorta and pulmonary artery are separate vessels. In Truncus Arteriosus, one major artery or trunk serves as the common pathway for the pulmonary artery and aorta. This trunk or major artery arises from the right and the left ventricles. Thus, deoxygenated blood (from the pulmonary artery) and oxygenated blood (in the aorta) mixes in one major trunk.
Hypoplastic Left Heart Syndrome
In Hypoplastic left heart syndrome, the left side of the heart is non-functional. The left ventricle, which pumps blood to the systemic circulation, lacks sufficient strength to pump the blood into the systemic circulation. This results to the hypertrophy of the right ventricle as it tries to maintain the adequate heart function and action.
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