Congenital heart disease characterized by
underdevelopment of the left side of the heart. Lethal in 25% of infants
during the first week of life.
Congenital disorder. Recurrence rate is 2% in siblings
of an affected infant. Condition is fatal without palliative surgery.
0.1-0.27:1000 live births.
Multifactorial; a subgroup showing autosomal
recessive inheritance may exist.
Range of abnormalities, including aortic atresia/stenosis,
hypoplastic left ventricle, hypoplasia of the aortic arch,
and mitral atresia or hypoplasia. The left ventricle is nonfunctional;
systemic perfusion is maintained by the right ventricle through a patent
ductus. Coronary perfusion occurs by retrograde flow through the aortic
arch. Pulmonary venous blood usually mixes with systemic venous blood
through an atrial septal defect or patent foramen ovale. Most neonates have
a degree of interatrial mixing, allowing sufficient pulmonary blood flow
with mild pulmonary venous hypertension. Unrestricted communications cause
increased pulmonary flow, pulmonary hypertension, and systemic
hypoperfusion. The absence of interatrial mixing results in pulmonary
hypertension and congestion and marked hypoxia as a consequence of low
pulmonary blood flow. The pulmonary and systemic circulations are supplied
in parallel by the right ventricle. Systemic perfusion and oxygenation are
dependent on maintaining a fine balance between pulmonary and systemic flow.
Neonatal cyanosis and symptoms and signs of right
ventricular failure. Echocardiography is diagnostic.
Neonatal tachypnea, tachycardia, cyanosis, third
heart sound, systolic murmur, and hepatomegaly. Chest radiograph may show
cardiomegaly and increased pulmonary vasculature. Neonatal cardiovascular
palliation is achieved by the Norwood procedure, which results in the right
ventricle supplying systemic circulation. The pulmonary circulation is
supplied by a systemic-to-pulmonary arterial shunt (e.g., Blalock-Taussig
shunt). An atrial septectomy is performed to allow pulmonary venous blood to
flow freely into the right atrium. At approximately 6 months, once pulmonary
vascular resistance has fallen from the high neonatal level, a hemi-Fontan
or bidirectional Glenn shunt is performed. This procedure results in the
pulmonary circulation being supplied by the superior vena cava (passive
process relies on superior vena cava pressure being greater than pulmonary
venous pressure to maintain flow). The Fontan procedure is completed at
least 6 months later to allow development of optimal right ventricular
function. The completed procedure results in both superior vena cava and
inferior vena cava blood being diverted to passively supply the pulmonary
circulation. Heart transplantation may be required.
History and examination to elicit
signs and symptoms of poor ventricular function. Poor ventricular function
should be considered to represent greatly increased anesthetic risk. Define
stage of palliation and hence physiologic requirements for anesthesia.
Cardiac function/physiology. Review recent echocardiograms and cardiac
catheterization data. Assess dependence on inotropes and the need for
prostaglandin E1 in the neonatal period to maintain the patent ductus
arteriosus. Measure normal SaO2, and
consider measurement of blood gases. Assess for abnormal renal function,
abnormal liver function, and the presence of a lactic acidosis suggestive of
poor systemic perfusion.