Chapter 80: Cyanotic Congenital Heart Disease

BACKGROUND

Epidemiology

Congenital heart defects (CHDs) are the most commonly reported major birth defect. Severe CHDs, the forms requiring early treatment at a cardiac center, have an incidence of approximately 3 per 1000 live births; the majority of these are cyanotic lesions. Although the overall incidence has climbed over the years, perhaps because of improved diagnostic methods such as echocardiography, the incidence of the major cyanotic types has remained fairly stable.

Etiology

The vast majority of CHDs are idiopathic. However, there are many known risk factors and associations.

1. Risk factors include

   1. Maternal diabetes;

   2. Maternal antihypertensive medications;

   3. Maternal retinol/high-dose vitamin A intake;

   4. Maternal lithium treatment (increased risk of Ebstein anomaly); and

   5. Maternal rubella.

2. Genetic causes are numerous, with more added all the time, including

   1. Trisomies;

   2. Williams-Beuren syndrome;

   3. DiGeorge velocardiofacial syndrome (deletion 22q11);

   4. Turner and Noonan syndromes;

   5. Alagille syndrome;

   6. CHARGE (coloboma, heart defects, choanal atresia, mental retardation, genitourinary and ear anomalies) association;

   7. Costello syndrome; and others.

3. There are syndromes/sequences without known genetic markers, such as VACTERL (vertebral, anal, cardiac, tracheoesophageal, renal, and limb) association.

EVALUATION AND WORKUP

Pathophysiology

The differential diagnosis of the cyanotic neonate begins with a pathophysiologic question: Is the etiology intrapulmonary shunting, intracardiac shunting, or alveolar hypoventilation (Figure 80-1)?

1. A thorough physical examination (Table 80-1), chest radiograph (Table 80-2), and hyperoxia test can distinguish congenital heart disease from parenchymal lung disease and central nervous system depression as etiologies of central cyanosis (Figure 80-2).

2. Conceptually, the hyperoxia test assesses whether there is a diffusion barrier in the lungs that limits oxygenation or whether there is shunting of deoxygenated blood into the systemic circulation at the cardiac level.