Neonatal Complex Heart Abnormalities
In this abnormality the great arteries exiting the heart are connected to the incorrect pumping chambers; the lung artery is connected to the left-sided pumping chamber (left ventricle) while the aorta is connected to the right-sided pumping chamber (right ventricle). This results in blue blood coming back to the right heart and being pumped to the body while red blood (with oxygen) that has come from the lungs to the left heart is pumped straight back into the lungs. This parallel circulation makes it difficult for the body to receive oxygenated blood from the lungs and results in a blue baby. Getting blood with oxygen to the body is only achieved by mixing of blood in the heart through a hole between the 2 top chambers (ASD) and sometimes a hole between the two pumping chambers (VSD, present in 30% of babies with transposition). The ductus arteriosus (a large artery connecting the lung artery with the aorta) also assists with mixing of red and blue blood. This is kept open in the first few days of life using a medication called prostaglandin.
This condition is now frequently detected during pregnancy with routine screening ultrasounds and confirmed with fetal echocardiography. The final diagnosis is confirmed after birth with transthoracic echocardiography. Diagnosis after birth often occurs when a baby is noted to have low oxygen levels in the newborn period. Often the hole between the 2 top chambers of the heart is not of adequate size to allow effective mixing of blood before the surgical repair. A procedure to enlarge this hole is performed by feeding a small catheter through a vein into the heart and stretching the hole to enlarge it using a balloon. The complete surgical repair is then performed a few days after birth. If there is a hole between the two pumping chambers (ventricular septal defect, VSD) then the left ventricle is kept well-pressurized and the repair can be performed in the first 1-6 weeks of life.
The surgical repair is called an Arterial Switch Operation and is open heart surgery requiring use of the heart-lung machine. It involves closing the holes inside the heart, switching the aorta and lung (pulmonary) artery to connect them to the correct pumping chambers (aorta to left ventricle, pulmonary artery to right ventricle) and tying and dividing the ductus arteriosus. The tiny arteries carrying blood to the heart muscle (coronary arteries) need to be moved separately as otherwise they may be kinked or distorted in the process. The operation takes about 5-6 hours and is usually followed by 3-5 days in the intensive care unit followed by 7-10 days on the ward to allow full recovery. About 10% of children undergoing this procedure will require further heart surgery at some point in their life and therefore lifelong follow-up is important.
Truncus arteriosus is a condition in which there is a single arterial outlet from the heart instead of a separate lung artery exiting the right heart and the aorta exiting the left heart. There is a large hole between the two pumping chambers sitting underneath this single large artery so that both red blood from the left heart and blue blood from the right heart can mix and exit the heart through the single arterial outlet. The lung arteries arise as branches from this single large artery. This condition can eventually become life-threatening if untreated due to excess blood flow to the lungs causing elevated blood pressure in the lungs and eventually heart failure.
Because there is so much blood going to the lungs with this arrangement the baby does not appear blue but becomes breathless, and has difficulty feeding and gaining weight due to increased work of breathing. After reviewing your baby’s symptoms and performing a physical examination, your doctor will usually order an echocardiogram to visualize the defect and confirm the diagnosis. Often this abnormality is detected during fetal life with screening ultrasounds and is confirmed by fetal echocardiography. The final diagnosis is confirmed after birth with transthoracic echocardiography.
Truncus arteriosus needs surgical repair that is generally performed in the first few weeks of life. It involves open heart surgery, use of the heart-lung machine, closing the hole in the heart with a patch, disconnecting the lung arteries from the aorta and connecting them to the right heart using a tube (conduit) that may or may not contain a valve. The aorta is also reconstructed where the lung arteries were removed. The hospital stay is usually 10 days to 2 weeks following the surgery. Children born with truncus arteriosus will always require at least one further surgery to replace the conduit connecting the lung arteries to the right heart. This is usually replaced with a valved conduit later in life as the child outgrows the original conduit. Regular cardiology follow-up after the primary repair is therefore very important.
Veins form within the lungs during their development that need to connect to the top chamber of the left side of the heart (left atrium) to bring red blood with oxygen to the left heart which can be then sent to the body through the aorta. Sometimes this process does not occur correctly and the lung veins instead connect to each other and then drain into a large vein, which then connects to the right side of the heart. This means that red blood from the lungs mixes with blue blood coming back to the right heart from the body and the baby may appear to be blue. This “blueness” is often not obvious and is frequently detected by observing reduced oxygen levels on a routine newborn check.
Because the pathway to get blood out of the lung veins is long and abnormal it can be partly blocked and the lungs become congested with blood. This makes it difficult for the baby to breathe and increases the pressure in the lung arteries. There is also a hole between the 2 top chambers of the heart to allow blood to get into the left heart from the right heart and out to the rest of the body through the aorta. A newborn baby with this condition may be more sleepy than usual and have difficulty breathing and feeding.
This condition is usually diagnosed soon after birth but may also be diagnosed on prenatal screening tests and confirmed with a fetal echocardiogram.
Surgery is usually necessary to repair this defect. The timing of surgery depends on how symptomatic the baby is and the structure of the abnormal venous connections. Surgery involves connecting the lung veins to the top chamber of the left side of the heart, disconnecting them from their abnormal attachment and closing the hole between the 2 top chambers of the heart. This involves open-heart surgery and use of the heart-lung machine to support the circulation during the repair. Babies are often in hospital for 1-3 weeks following this surgery depending on how they respond to the operation. Regular follow-up with your child’s cardiologist is required following the repair to detect any narrowing or scarring that can occur at the repair site connecting the veins to the heart.