What is fetal critical aortic stenosis?
Blood flows from the heart through the aortic valve to the rest of the body. The term 'aortic stenosis', refers to a narrowing of this valve, resulting in an obstruction of blood flow. Critical aortic stenosis affects about 6 in every 1000 infants born and occurs more often in boys. It may be an isolated defect or occur with other heart problems.
The tighter the opening, the harder the left ventricle (left-sided pumping chamber of the heart) works in an effort to meet the demands of the body. If left untreated, this burden results in a thickening of the heart muscle, called hypertrophy. The muscle is damaged and does not function normally, resulting in left-sided heart failure and, subsequently, failure of LV growth and development. This can result in hypoplastic left heart syndrome at the time of birth.
Infants born with critical aortic stenosis have an opening so small it is impossible for the heart to pump enough blood to meet the baby's needs. If treatment is not initiated shortly after birth, the baby will develop congestive heart failure and shock. Usually, a medication called prostaglandin is used to keep the ductus arteriosus open. The ductus is a small blood vessel that connects the pulmonary artery with the aorta and provides a way for blood to get out to the body. Blood that bypasses the lungs using the ductus arteriosis has lower levels of oxygen so the baby appears somewhat blue.
How is the diagnosis made?
Routine prenatal ultrasounds can detect a problem with the baby's heart. Aortic stenosis can be identified by fetal echocardiogram as early as 16 weeks into the pregnancy. When critical aortic stenosis is present in the mid-trimester fetus, the left ventricle becomes dilated and dysfunctional. As a result, there is less blood flow through the left heart contributing to a halt in the growth of the left ventricle. The outcome is similar to hypoplastic left heart syndrome at the time of the delivery.
Is there fetal treatment for critical aortic stenosis?
Fetal treatment is available for select fetuses. Potential candidates for fetal cardiac intervention will be identified from the patients who are referred to the University of Michigan Prenatal Heart center with fetal cardiac disease. In utero intervention to correct the anatomical defect has the potential to alter the natural history of the disease, which may lead to a significant improvement in the outcome.
With the mother under general anesthesia, a needle and catheter is passed through the uterus and into the fetal heart. The aim of in utero intervention is to open the stenotic aortic valve with a balloon catheter before the growth of the left ventricle is negatively effected. If normal blood flow can be restored, a left ventricle with more adequate size and function may be present at birth.
What other treatment is available for aortic stenosis?
Medical interventions for patients with aortic stenosis depend on several factors including the location of the narrowing, severity of narrowing, size of the left ventricle, associated cardiac problems, symptoms, age and size. Please consult your doctor or follow this link for more information.
Are there special considerations planned for the delivery?
It is recommended that the delivery is planned at a hospital that is prepared for high-risk deliveries that also includes a neonatal intensive care, pediatric cardiology and pediatric cardiothoracic services. This will help facilitate coordination of care between specialties and permit access to other emergency services if needed.
Can this happen again with another pregnancy?
Left sided heart problems can recur in families where one child is affected. Estimates of having another child affected with a heart defect range from 4.5 to 13% (Boughman et al. 1993, Brenner et al. 1989). When a heart defect recurs in another child, it is not necessarily the same heart defect, and can be something more minor or just as severe. Your doctor and a genetic counselor will meet with you and discuss your family's risk.