Hypoplastic Right Heart Syndrome (HRHS)
Hypoplastic Right Heart Syndrome (HRHS) is a range of right-sided congenital heart defects in which the right-sided structures (tricuspid valve, right ventricle and/or pulmonary valve) are underdeveloped or not formed. When these structures are too small or do not function properly, the right side of the heart cannot send enough blood to the lungs. This causes a baby with untreated HRHS to have abnormally low oxygen levels. The treatments for HRHS have developed substantially in the last few decades and are tailored to each baby’s needs.
Some congenital heart defects in the range of HRHS are:
- Tricuspid stenosis: The tricuspid valve between the right atrium and right ventricle is too small
- Tricuspid atresia: The tricuspid valve between the right atrium and right ventricle is not formed
- Pulmonary stenosis: The pulmonary valve between the right ventricle and pulmonary artery is too small
- Pulmonary atresia: The pulmonary valve between the right ventricle and pulmonary artery is not formed
HRHS is less common than Hypoplastic Left Heart Syndrome (HLHS), which is an underdevelopment of the left side of the heart.
If your doctor suspects a fetal heart anomaly after reviewing your routine ultrasound, he or she may request a fetal echocardiogram (echo), an ultrasound of the fetus’s heart. This safe, noninvasive test shows the structure of the heart and how it is functioning, which can help us confirm the diagnosis of HRHS and discuss possible options for treatment after delivery. Our fetal heart team will monitor the baby closely for the remainder of the pregnancy.
What You Need to Know About HRHS
Most babies with HRHS can be delivered vaginally at full-term, unless there are obstetric indications for another mode of delivery. It is best for these babies to be delivered at a medical center where there is access to a team of pediatric cardiologists and neonatologists, along with an established Neonatal Intensive Care Unit (NICU).
The Fetal Heart Program at the Cardinal Glennon St. Louis Fetal Care Institute has the experience, facilities and technology to handle the most medically challenging deliveries. In the most severe cases the team can perform a Cesarean Section at SSM Health Cardinal Glennon Children’s Hospital. If additional intervention is needed, the baby is next door to the pediatric operating room and the pediatric hybrid cardiac catheterization suite.
After delivery, your baby will need prostaglandin (PGE), an intravenous medication that keeps the patent ductus arteriosus (a normal connection present in babies in the womb) open. The patent ductus arteriosus (PDA) will allow blood to get to the lungs.
In some cases, a cardiac catheterization may be required to perform a balloon atrial septostomy in the first few days of life. This x-ray guided procedure is typically done by placing a thin flexible tube, or catheter, through the umbilical vein (a vessel in the umbilical cord) and does not require an incision. A balloon atrial septostomy creates a larger hole between the top chambers of the heart.
The interventions for HRHS vary depending on which structures are abnormal. In cases where the pulmonary valve is not opening well, cardiac catheterization may be performed to help open the valve. In less severe cases this may allow the right heart to function adequately.
In more severe cases, the right heart is too small to send enough blood to the lungs. Shortly after the baby’s birth, surgeons perform the first of a series of surgeries done to increase blood flow to the lungs and bypass the poorly functioning right side of the heart. These surgeries are not able to cure HRHS, but provide for a functioning heart.
Blalock-Taussig (BT) Shunt: This procedure usually occurs within the first week of life. In this surgery, the surgeon inserts an artificial tube to provide blood flow to the lungs. There is still mixing of oxygen poor and oxygen rich blood through the hole between the top chambers of the heart.
Glenn Procedure: This procedure typically occurs between 4 and 6 months of age. This surgery creates a direct connection between the pulmonary artery and the superior vena cava (vessel returning oxygen-poor blood from the upper part of the body to the heart). This reduces the amount of blood flow returning to the small right side of the heart by allowing blood returning from the upper body to flow directly to the lungs.
Fontan Procedure: This procedure typically occurs between 2 and 4 years of age. This surgery connects the pulmonary artery and the inferior vena cava (vessel returning oxygen-poor blood from the lower part of the body to the heart), allowing the blood coming back from the lower body to go to the lungs. Once this procedure is complete, oxygen-rich and oxygen-poor blood no longer mix in the heart. The surgeon may leave a small connection between the oxygen rich and oxygen poor chambers (a fenestration).
After the first surgery your baby may be fragile and have feeding difficulties because the heart is still working very hard. These babies will require a stay in the Neonatal or Pediatric Intensive Care Unit (NICU or PICU) until they overcome any feeding and breathing difficulties. Following these surgeries, these children will need lifelong follow-up visits with a cardiologist to monitor their progress.
The long-term prognosis varies depending on the severity of the initial defect. Children with HRHS whose hearts become weak may eventually need heart transplants. The three-step procedure for HRHS was only introduced in the 1980s. Surgical techniques have changed significantly since that time, and continue to improve.