Diagram of a healthy heart and one suffering from Hypoplastic left heart syndrome. In the heart on the right, note the near absence of the left ventricle, which normally provides systemic circulation. In the Norwood procedure, blood flow from the right ventricle is rerouted to serve this function, which means that an alternative source of pulmonary circulation must be provided.
Cardiopulmonary bypass is required.
In these conditions, the most urgent problem is that the heart is unable to pump blood to the systemic circulation (i.e. to the body). The goal of the Norwood procedure is to connect the single ventricle to the systemic circulation. To accomplish this, blood flow to the lungs is disrupted, and therefore an alternative path must be created to supply the lungs.
Entry to the body cavity for the Norwood Procedure is gained by a vertical incision above the sternum. Separation of the sternum is necessary.
The surgery on the heart can be divided into two main steps.
Providing systemic circulation 
The main pulmonary artery is separated from the left and right portions of the pulmonary artery and joined with the upper portion of the aorta. Widening of the pulmonary artery is often necessary, and may be accomplished by using the patient's existing biological tissue, or appropriate animal tissue. This allows the blood, a mixture of oxygenated and deoxygenated, to be pumped to the body via the morphologic right ventricle, through the pulmonary valve.
Providing pulmonary circulation 
Since the remainder of the pulmonary artery is now disconnected from the heart, one of a few techniques must be used to supply blood to the lungs:
- With a modified Blalock-Taussig Shunt, a Gore-Tex conduit (a kind of plastic tubing) is used to connect the subclavian artery to the pulmonary artery. In this case, blood comes from the single ventricle, through the pulmonary valve, the reconstructed aorta, the subclavian artery, and the conduit, to the lungs. There are variations on this procedure where the origin of the shunt is elsewhere in the systemic circulation (e.g. from the aorta itself) rather than the subclavian artery.
- With a Sano shunt, a hole is made in the wall of the single ventricle, and a Gore-Tex conduit is used to connect the ventricle to the pulmonary artery. The key difference here is that the blood flow is more pulsatile than with the Blalock-Taussig version.
After this first step (switching the right ventricle in functional position of the absent left ventricle) children generally proceed down the path to a Fontan procedure.
- Norwood WI, Lang P, Casteneda AR, Campbell DN. Experience with operations for hypoplastic left heart syndrome. J Thorac Cardiovasc Surg. Oct 1981;82(4):511-9.
- Norwood WI, Lang P, Hansen DD. Physiologic repair of aortic atresia-hypoplastic left heart syndrome. N Engl J Med. Jan 6 1983;308(1):23-6. [Medline].
- Ricardo Munoz; Victor Morell; Peter Wearden (August 2009). Critical Care of Children with Heart Disease: Basic Medical and Surgical Concepts. Springer. pp. 326–. ISBN 978-1-84882-261-0. Retrieved 21 June 2011.
- A. Corno; Gigi P. Festa (8 December 2008). Congenital Heart Defects. Decision Making for Surgery: CT-Scan and Clinical Correlations. Springer. pp. 123–. ISBN 978-3-7985-1718-9. Retrieved 24 June 2011.