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NEONATAL PALLIATION OF HYPOPLASTIC LEFT HEART SYNDROME: THE NORWOOD
PROCEDURE
RICHARD A. JONAS
CHILDREN’S NATIONAL MEDICAL CENTER, A.B.D.
The first stage Norwood procedure was introduced by Norwood in 1983 for initial
palliation of this challenging condition. The fundamental principles remain unchanged
from Norwood’s initial description, namely reconstruction of a neoaorta whereby the
pulmonary artery is connected to the aorta, an atrial septectomy to allow unobstructed
pulmonary venous return and a shunt for controlled pulmonary blood flow. Although
various modifications of the Norwood procedure have been suggested there is now
general agreement that supplementary tissue is required in order to allow tension
free reconstruction of the neoaorta with minimal risk of growth related neoaortic
obstruction. Controversy continues around the optimal mode of supplying pulmonary
blood flow, whether a modified Blalock shunt or Sano shunt from the right ventricle to
the pulmonary artery bifurcation. The Sano shunt has the advantage of avoiding run
off during diastole which may critically compromise coronary blood flow. There is little
if any place for the hybrid procedure which prolongs the fetal circulation which is now
known to compromise cerebral blood flow.
Results of the Norwood procedure have consistently improved over the nearly three
decades since the operation was introduced. Many centers today report an early
mortality of 10% or less. Important risk factors for early mortality include prematurity,
important extracardiac anomalies, a particularly diminutive ascending aorta and the
presence of prenatal obstructed pulmonary venous return.
Management During the Interval Period Between Neonatal Palliation and Second
Stage Palliation
The interval period between the first and second stage procedures for hypoplastic left
heart syndrome is a critically important period where there can be life threatening
instability. Pulmonary vascular resistance falls during this time and may steal blood
from the coronary circulation, particularly if there is a Blalock shunt rather than a Sano
shunt. Fibrosis of ductal tissue can result in arch obstruction developing which can be
difficult to diagnose by echocardiography. Stenosis of the central pulmonary arteries
may develop and the atrial septum may fibrose and become restrictive. For all these
reasons it is critically important that the child should be intensively monitored during
the interval period.
Cardiac Catheterization or MRI Before Stage 2 Palliation
As cardiac MRI evolves it has becomes a reasonable alternative to cardiac catheterization
as a pre stage 2 investigation. Areas of particular importance are the aortic arch as well
as the central pulmonary arteries.