Overriding aorta is a congenital heart defect where the body’s main artery, the aorta, is positioned abnormally. This condition is present at birth, developing during fetal growth. In a healthy heart, the aorta originates solely from the left ventricle, the heart’s strong pumping chamber that sends oxygen-rich blood to the body. However, with an overriding aorta, this crucial blood vessel is misaligned, affecting how blood circulates throughout the body.
Understanding Overriding Aorta
An overriding aorta occurs when the aorta is situated directly above a hole in the wall separating the two lower chambers of the heart, known as a ventricular septal defect (VSD). Instead of being connected only to the left ventricle, the aorta effectively “overrides” this defect, receiving blood from both the right and left ventricles. This abnormal positioning means that blood from the right ventricle, which is typically oxygen-poor and destined for the lungs, can enter the aorta and be pumped to the body.
The consequence of this anatomical arrangement is the mixing of oxygenated and deoxygenated blood within the aorta. When the aorta overrides a VSD, some oxygen-poor blood bypasses the lungs and is distributed to the body. This reduces the overall amount of oxygen delivered to the body’s tissues, potentially affecting various bodily functions. The degree to which the aorta overrides the VSD can vary, influencing the severity of this mixing.
Associated Conditions and Causes
Overriding aorta is most commonly recognized as one of the four principal defects found in Tetralogy of Fallot, a complex congenital heart condition. The other three defects in Tetralogy of Fallot include a ventricular septal defect (VSD), pulmonary stenosis (a narrowing of the pulmonary artery), and right ventricular hypertrophy (thickening of the right ventricle’s muscle wall).
While primarily associated with Tetralogy of Fallot, an overriding aorta can also occur in isolation or as part of other rare and complex congenital heart defects. The exact reasons why congenital heart defects like overriding aorta develop are often not fully understood. They are believed to result from a combination of genetic and environmental factors that disrupt the normal formation of the heart during fetal development. These factors can include certain genetic syndromes or environmental exposures during pregnancy, though in many cases, a specific cause is not identified.
Diagnosis and Recognizable Symptoms
Diagnosis of an overriding aorta typically begins with medical imaging. Prenatal ultrasound can sometimes identify structural heart abnormalities before birth, allowing for early detection. After birth, a physical examination might reveal a heart murmur, which prompts further investigation.
The definitive diagnostic tool is an echocardiogram, an ultrasound of the heart, which provides detailed images of the heart’s structure and blood flow. This imaging allows healthcare professionals to visualize the aorta’s position relative to the ventricular septum and assess the degree of override. Other imaging tests, such as a chest X-ray, cardiac MRI, or CT scan, may also be used to gather more information about the heart and surrounding structures.
Symptoms that might indicate an overriding aorta often stem from the reduced oxygen delivery to the body. Common signs in infants include cyanosis, a bluish discoloration of the skin, lips, or nail beds, due to low oxygen levels in the blood. Other symptoms can involve shortness of breath, particularly during feeding or physical activity, fatigue, and difficulty gaining weight. These symptoms often lead parents to seek medical attention.
Management and Treatment Approaches
The management of an overriding aorta involves addressing the underlying congenital heart defect, such as Tetralogy of Fallot. Surgical repair is the primary treatment approach for correcting the anatomical abnormalities and restoring proper blood flow. This surgery is often performed during infancy, depending on the severity of the condition and the infant’s overall health.
The goals of surgical intervention typically include closing the ventricular septal defect, which helps to separate the blood flow from the left and right ventricles. Additionally, if pulmonary stenosis is present, the surgery aims to widen the narrowed pulmonary artery to improve blood flow to the lungs. Following surgical repair, individuals require lifelong follow-up care with a cardiologist to monitor heart function and address any potential long-term concerns.