20. Congenital Heart Disease
KeywordsNon-cardiac anesthesia in cardiac childPediatric anesthesia, heart murmurAnesthesia and the Fontan circulationEndocarditis prophylaxisCongenital heart disease, preoperative assessment
Congenital heart disease occurs in 6–10 per 1000 births and is one of the most common congenital defects.
Ninety percent of children born with congenital heart disease survive into adulthood and will present for non-cardiac surgery having had varying levels of surgical correction. This chapter focuses on the management of children for non-cardiac surgery, and the assessment of a child with a murmur.
20.1 Types of Congenital Heart Disease
Classification of congenital heart disease by main physiological defect
Types of congenital heart disease
1. ‘Simple’ left-to-right shunt with increased pulmonary blood flow
Atrial septal defect (ASD)
Ventricular septal defect (VSD)
Patent ductus arteriosus (PDA)
Atrioventricular septal defect (AVSD)
2. ‘Simple’ right-to-left shunt with decreased pulmonary blood flow
Tetralogy of Fallot (TOF)
Pulmonary atresia (with shunting of blood through associated defect
Tricuspid atresia (with shunting of blood through associated defect)
Ebstein’s anomaly (Tricuspid obstruction with ASD or patent foramen ovale)
3. ‘Complex’ shunts: mixing of pulmonary and systemic blood flow causing cyanosis
Transposition of the Great Arteries (TGA)
Total anomalous pulmonary venous drainage
Double-Outlet Right Ventricle (DORV)
Hypoplastic Left Heart Syndrome (HLHS)
4. Obstructive lesions
Coarctation of the aorta
Hypoplastic aortic arch
20.1.1 Shunting of Blood Between the Systemic and Pulmonary Circulations
18.104.22.168 Left-to-Right Shunts
22.214.171.124 Right-to-Left Shunts (Cyanotic Heart Disease)
De-oxygenated blood from the right side of the heart bypasses the lungs and mixes into the systemic circulation, causing cyanosis. This occurs in lesions such as a Tetralogy of Fallot (TOF). This is a more debilitating condition than left-to-right shunting as pulmonary blood flow is often reduced. Most cyanotic heart conditions have complex defects allowing variable mixing of blood between the right and left side of the heart, and the degree of mixing is affected by the balance between the pulmonary and systemic vascular resistances. If pulmonary vascular resistance increases, pulmonary blood flow decreases. However, the pulmonary blood flow is also affected by the systemic vascular resistance. If the systemic vascular resistance falls, more blood is shunted to the left side of the heart and pulmonary blood flow decreases. The balance between the pulmonary and systemic vascular resistances is the critical factor with anesthesia for children with cyanotic heart disease.
Differences between the two types of pulmonary-systemic shunting of blood
Normal arterial SaO2
Inhalational induction faster
IV induction slower
Risk from IV air bubbles slightly raised
Anesthesia generally well tolerated
Cyanosed, minimal improvement with high FiO2
High risk from IV air bubbles
Inhalational induction slower
IV induction faster, reduced dose required
The balance between the pulmonary and systemic vascular resistances is the critical factor in anesthesia for children with cyanotic heart disease.
126.96.36.199 Duct-Dependent Heart Disease
Some children with cyanotic heart disease have very little blood flow from the right ventricle into the pulmonary artery and lungs. Although this is not a problem while the placenta is in the circulation, after birth it results in poor oxygenation and may not be compatible with survival. Some of these children rely on the ductus arteriosus that directs blood from the aorta into the pulmonary artery. This oxygenated blood from the aorta mixes with any de-oxygenated blood already in the pulmonary artery and then passes into the lungs. Although this is not efficient for oxygenation, it often permits survival, albeit with persisting cyanosis. These babies have duct-dependent cyanotic heart disease, and their ductus is kept open with prostaglandins until other methods of augmenting pulmonary blood flow can be achieved. These methods depend on the underlying cardiac problem but include atrial septostomy (in transposition of the great arteries) or a modified Blalock-Taussig shunt (modified BT shunt). A modified BT shunt connects the left or right subclavian artery to the left or right pulmonary artery with a synthetic graft.
If an infant has a modified BT shunt, pulmonary blood flow depends on the systemic blood pressure. Increasing the SVR and blood pressure will improve the child’s saturation.
20.1.2 ASD and VSD
Children with an atrial septal defect (ASD) or ventricular septal defect (VSD) have a predominantly left-to-right shunt that increases pulmonary blood flow and causes volume overload of the right ventricle. The size of the defect and difference in chamber pressures determine the amount of shunting. Patients with small restrictive defects have minimal left to right shunting and minimal increase in pulmonary blood flow. On the other hand, patients with large non-restrictive defects have greatly increased pulmonary blood flow.
Both defects are associated with a systolic murmur maximal at the left sternal edge. Small defects may eventually close without treatment. Others require either surgical closure under cardio-pulmonary bypass or using a transvenous approach in the catheter lab.
As long as pulmonary hypertension has not developed, anesthetic management is relatively straightforward. Preload should be maintained, and the fall in systemic vascular resistance that tends to accompany anesthesia reduces left-to-right shunting. Although increasing pulmonary vascular resistance also reduces shunting, PVR is not deliberately manipulated. Inhalational induction is very rapid because of the increase in pulmonary blood flow, but intravenous induction is delayed because of recirculation of agent through the shunt and pulmonary circulation (Table 20.2). In practice however, the change from the normal speed of induction is not great. Paradoxical air embolism can occur during ventilation if high airway pressures are used—IPPV and PEEP increase right atrial pressure and can induce R-to-L shunting.
20.1.3 Tetralogy of Fallot
Overriding aorta (the aorta is positioned over the VSD, communicating with the left and right ventricles)
Right ventricular hypertrophy
Right ventricular outflow tract obstruction (subvalvular, valvular and/or supravalvular)