Rebuilding Circulation in Three Acts
For a baby born with hypoplastic left heart syndrome, there is no way to fix the tiny, underpowered left ventricle. Instead, surgeons redesign the heart’s plumbing so that the right ventricle takes over the job of the left. This isn’t a single operation, but a carefully timed three-stage reconstruction that unfolds over years.
Stage I: The Norwood or Hybrid – Buying Time
In the first days of life, the Norwood procedure transforms the newborn’s circulation. Surgeons enlarge the narrow aorta with a patch so it can carry blood to the body and connect it to the right ventricle—now the systemic pump. Because that ventricle can no longer send blood directly to the lungs, a shunt is created to route some blood from either the subclavian artery (Blalock–Taussig shunt) or the right ventricle (Sano shunt) into the pulmonary arteries.
This lifesaving operation is long and technically demanding, and the baby is medically fragile afterward, often with feeding difficulties and low oxygen levels due to mixing of blue and red blood in the right ventricle.
An alternative, the Hybrid procedure, avoids putting the newborn on a heart-lung machine. Instead, a stent keeps the ductus arteriosus open, and bands placed around the pulmonary arteries restrict excessive lung blood flow. It’s shorter—often one to two hours—with outcomes comparable to the Norwood.
Stage II: The Glenn – Relieving the Strain
At about three to six months of age, the second stage, the bidirectional Glenn or Hemi-Fontan procedure, shifts some of the workload away from the overtaxed right ventricle. Surgeons disconnect the superior vena cava—the large vein carrying blood from the head and upper body—from the heart and attach it directly to the pulmonary arteries.
Now, venous blood from the upper body flows passively into the lungs without passing through the heart. The earlier shunt is removed, and the lungs are no longer exposed to the high, systemic pressures that can cause long-term damage. Oxygen levels improve, though blood from the lower body still mixes in the right ventricle, leaving some residual blueness.
Stage III: The Fontan – Completing the Circuit
Between roughly two and five years of age, the Fontan procedure finishes the rerouting. Venous blood from the lower body, returning via the inferior vena cava, is channeled directly to the pulmonary arteries, bypassing the heart entirely. There are variations in how surgeons create this pathway, but the goal is the same: all venous blood flows passively to the lungs; the right ventricle pumps only oxygenated blood to the body.
The result is a “single-ventricle physiology”: two upper chambers and two lower chambers still exist anatomically, but only one ventricle is doing the pumping. It is a palliative solution, not a cure, but it allows an estimated 70% of children with HLHS to reach adulthood.
A New Kind of Circulation
The three-stage pathway turns an unviable newborn circulation into a workable, though permanently altered, system. Each step trades one set of risks for another, but together they create something extraordinary: a way for a right ventricle, never meant to power the whole body, to sustain a life into the future.