The Norwood procedure is an open-heart surgery performed on newborns whose hearts developed with only one working pumping chamber instead of two. It is most commonly done for babies born with hypoplastic left heart syndrome (HLHS), a condition where the left side of the heart is too small to pump blood to the body. Without surgery, this condition is fatal. The Norwood is the first of three planned surgeries that gradually rebuild the heart’s circulation so the single working chamber can do the job of two.
Why the Surgery Is Needed
In a typical heart, the right ventricle pumps blood to the lungs and the left ventricle pumps oxygen-rich blood to the rest of the body. In babies with HLHS, the left ventricle, the left-side valves, and the aorta are severely underdeveloped. The baby survives the first hours or days of life only because a temporary blood vessel connection (the ductus arteriosus) that all babies have at birth is still open, allowing some blood to reach the body. Once that connection closes naturally, the baby’s circulation fails.
HLHS is the most common reason for a Norwood, but the surgery also applies to other conditions where only one ventricle works properly, including double-inlet left ventricle, hypoplastic right heart syndrome, and tricuspid atresia. The common thread is that only one pumping chamber is strong enough to sustain circulation, and the heart needs to be restructured so that single chamber can handle blood flow to both the lungs and the body.
What the Surgery Does
The Norwood procedure has three main goals: create an unobstructed path for blood to flow from the working ventricle to the body, ensure blood returning from the lungs can reach that ventricle, and establish a controlled source of blood flow to the lungs.
To accomplish this, the surgeon makes several structural changes during a single operation. First, they remove the wall between the two upper chambers of the heart (the atria). This allows oxygen-rich blood returning from the lungs to flow freely into the working right ventricle. Next, the surgeon connects the baby’s small, underdeveloped aorta to the larger pulmonary artery and uses a patch to widen it, creating a new, larger vessel called a neoaorta. This rebuilt aorta is then connected to the right ventricle so it can pump blood out to the entire body.
Since the pulmonary artery has been repurposed as the new aorta, the lungs need a new blood supply. The surgeon creates this by placing a small tube graft called a shunt. There are two main options:
- Modified Blalock-Taussig (BT) shunt: A small tube connecting a branch of the aorta to the pulmonary artery. This delivers continuous blood flow to the lungs during each heartbeat. The downside is that it diverts blood away from the coronary arteries during the resting phase of the heartbeat, which can sometimes reduce blood supply to the heart muscle itself.
- Sano shunt (RVPA shunt): A small tube connecting the right ventricle directly to the pulmonary artery. This avoids the coronary blood flow problem because it only delivers blood to the lungs when the ventricle squeezes. However, it requires a small incision in the ventricle wall, which can affect heart function over time and may lead to earlier timing of the second surgery.
The choice between shunts depends on the baby’s anatomy and the surgical team’s experience. Neither option is universally superior.
The Three-Stage Surgical Plan
The Norwood is Stage 1 of a three-surgery sequence, and it is performed in the first weeks of life. It is a bridge: it keeps the baby alive and growing, but the circulation it creates is not a permanent solution. The single ventricle is doing double duty, pumping blood to both the lungs and the body, which puts it under significant strain.
Stage 2, called the Glenn procedure, typically happens around 4 to 6 months of age. In this surgery, the vein carrying blood back from the upper body is connected directly to the pulmonary artery, reducing the workload on the single ventricle by routing some blood to the lungs passively, without the ventricle having to pump it.
Stage 3, the Fontan procedure, usually occurs between ages 2 and 4. It completes the restructuring by connecting the vein carrying blood from the lower body directly to the pulmonary arteries as well. After the Fontan, all blood returning from the body flows to the lungs by gravity and pressure alone, and the single ventricle is responsible only for pumping oxygenated blood to the body. This is the final configuration these children live with long-term.
The Interstage Period at Home
The weeks between the Norwood and the Glenn (called the interstage period) are the highest-risk window outside the hospital. The baby’s circulation depends entirely on a small shunt, and even minor illnesses can destabilize it. Most cardiac centers send families home with monitoring equipment and specific parameters to track daily.
Parents are typically asked to check oxygen saturation levels, daily weight, heart rate, and how much the baby is eating. The general targets give a sense of how closely this is monitored: oxygen saturations dropping to 75% or below is a red flag, as is an unexpected spike above 90% (which can signal a circulation problem). Weight loss of 30 grams or more, or failure to gain at least 20 grams over three days, triggers a call to the care team. Babies generally need to take in at least 100 mL per kilogram of body weight per day in feedings, with a target weight gain of 20 to 30 grams daily.
This level of home monitoring has significantly improved interstage survival at centers that use it. It can feel overwhelming for families, but it provides an early warning system that catches problems before they become emergencies.
Survival and Long-Term Outlook
The Norwood procedure is one of the most complex and high-risk surgeries in all of pediatric medicine. Survival has improved dramatically since the procedure was first developed in the early 1980s, but the numbers reflect the seriousness of the condition. A large study tracking over 2,000 patients who underwent staged reconstruction for HLHS between 1984 and 2023 found that transplant-free survival was 31% at 35 years. That number spans nearly four decades of surgical evolution, and outcomes for babies operated on in recent years are substantially better than for those in the 1980s and 1990s, as surgical techniques, intensive care, and interstage monitoring have all advanced.
The highest mortality risk occurs around the Norwood itself and the interstage period before the Glenn. Each subsequent stage carries lower surgical risk. After completing all three stages, many children attend school, play, and participate in a range of activities, though they require lifelong cardiac follow-up. Heart function, exercise capacity, and quality of life vary widely from person to person, and some patients eventually need a heart transplant later in life if the single ventricle begins to fail.
What Recovery Looks Like
After the Norwood, babies spend an extended period in the cardiac intensive care unit. They are on a ventilator initially, with multiple IV lines and monitoring equipment. The total hospital stay often stretches several weeks, depending on how the baby’s circulation stabilizes and whether complications arise. Feeding is one of the biggest challenges during recovery. Many babies need supplemental tube feeding before they can take enough by mouth to support adequate weight gain.
Between surgeries, babies are typically seen frequently by their cardiology team, with regular echocardiograms and oxygen saturation checks. Parents become deeply involved in day-to-day medical monitoring in a way that is unusual for most newborn care, and cardiac centers generally provide extensive education and support resources to help families manage this responsibility.