• Clinical science

Cyanotic congenital heart defects

Summary

Cyanotic heart defects are congenital cardiac malformations that commonly affect the atrial or ventricular walls, heart valves, or large blood vessels. Common causes include genetic defects (e.g., trisomies), maternal infections (e.g., rubella), and maternal consumption of drugs or alcohol during pregnancy. Pathophysiologically, cyanotic heart defects are often characterized by a right-to-left shunt, which results in deoxygenated blood entering the systemic circulation. The resulting hypoxemia manifests clinically as cyanosis, which may occur as acute, life-threatening episodes. Further symptoms include failure to thrive, characteristic heart murmurs, and symptoms of heart failure. The diagnosis is confirmed through visualization of the defect on echocardiography. Further diagnostic findings include low oxygen saturation and characteristic x-ray findings (e.g., decreased pulmonary markings). Heart defects requiring treatment are repaired via catheter procedures or surgery. Supportive medical therapy is required in cases of heart failure (e.g., diuretics, inotropic agents) or if surgery cannot be performed (e.g., prostaglandin). If untreated, most cyanotic heart defects are fatal within the first year of life.

Overview of cyanotic congenital heart defects

General pathophysiological processes

General clinical features

  • “Blue babies”: pale gray or blue skin color caused by cyanosis
  • Nail clubbing
  • Exertional dyspnea, tachypnea, and fatigue
  • Squatting for relief during hypoxemic episodes
  • Poor weight gain, failure to thrive
  • Characteristic heart murmurs
  • Features of underlying genetic syndromes
  • For specific features, see “Clinical features” in the subsections below.

Treatment

The “5 Ts” of cyanotic CHDs: Tetralogy of Fallot, Transposition of the great vessels, Tricuspid atresia, Total anomalous pulmonary venous return, and Truncus arteriosus

References:[1][2][3][4]

Tetralogy of Fallot

Definition

Tetralogy of Fallot is defined as the simultaneous occurrence of the following four defects:

  1. Right ventricular outflow obstruction (RVOT) due to pulmonary valve stenosis
  2. Right ventricular hypertrophy
  3. Ventricular septal defect (VSD)
  4. Overriding aorta (above the VSD)

Epidemiology

  • Most common cause of cyanotic CHD (∼ 4/10,000 live births in the US)

Etiology

  • Typically sporadic; sometimes associated with genetic defects (e.g., Down syndrome, DiGeorge syndrome)
  • Associated with other cardiac anomalies in ∼ 40% of patients

Pathophysiology

  • The extent of right ventricular outflow tract obstruction and central pulmonary hypoplasia determines the severity of hemodynamic dysfunction.
    • Mild obstruction → left-to-right shunt via VSD more pronounced → no cyanosis
    • Severe obstruction → right-to-left shunt via VSD more pronounced → severe cyanosis

Clinical findings

  • Mild cyanosis
  • Tet spells
    • Intermittent hypercyanotic, hypoxic episodes with a peak incidence 2–4 months after birth
    • Associated with psychological and physical stress (e.g., crying, feeding, defecation)
  • Untreated young children tend to squat.
  • Auscultatory finding: harsh systolic murmur that is best heard over Erb's point and left upper sternal border

Diagnostics

Treatment

References:[5][6][4][7][8][9]

Transposition of the great vessels (TGV)

Definition

Epidemiology

Etiology

Pathophysiology

Clinical findings

  • Postnatal cyanosis (not affected by exertion or supplemental oxygen)
  • Tachypnea
  • Auscultation
    • Single loud S2
    • If concurrent VSD is present: systolic murmur at the left sternal border

Diagnostics

Treatment

Without treatment, 90% of patients with transposition of the great vessels die within the first year of life!



References:[1][2][10][11][12][13][14]

Hypoplastic left heart syndrome

Definition

Epidemiology

Etiology

Pathophysiology

Clinical findings

Diagnostics

Treatment

Prognosis

  • Most children reach adult age.

Without treatment, 95% of patients with hypoplastic left heart syndrome die within their first month of life!
References:[15]

Tricuspid valve atresia

Definition

Epidemiology

Pathophysiology

Clinical features

  • Central cyanosis occurring within days after birth
  • Auscultation: if a concurrent VSD is present → rough holosystolic murmur over lower left sternal border

Diagnostics

Treatment

Without treatment, about 75% of patients with tricuspid atresia die in early childhood!
References:[2][16][17]

Total anomalous pulmonary venous return

Definition

Epidemiology

Etiology

  • Exact cause unknown; found in 20% of children with Down syndrome

Pathophysiology

Clinical features

Diagnostics

Treatment

  • Improve cardiac function in patients with heart failure (see “Treatment” in “Overview” section above)
  • Surgical repair

Without treatment, about 80% of patients with total anomalous pulmonary venous return die within the first year of life!
References:[2][18]

Ebstein anomaly

Definition

Epidemiology

Etiology

  • Prenatal lithium exposure
  • Isolated genetic defects

Pathophysiology

Clinical findings

Diagnostics

Treatment

Cyanosis usually worsens as the ductus arteriosus closes; IV prostaglandins should be administered to keep the ductus arteriosus open!

References:[19][1][1][20][2][21][22][23][24][25]

Persistent truncus arteriosus

Definition

  • Failed separation of aorta and pulmonary artery during development → single trunk that receives output from both ventricles

Epidemiology

Etiology

Clinical features

Diagnostics

Treatment

Without treatment, 85% of patients with persistent truncus arteriosus die within the first year of life!


References:[2][26]

Double aortic arch

Definition

Pathophysiology

Clinical findings

  • Typically manifests within the first weeks of life, especially in cases of tracheal compression
  • Tracheal constriction: inspiratory or expiratory stridor, dyspnea, respiratory arrest
    • Acute episodes of severe constriction and/or apnea with cyanosis may occur → possibly life-threatening!
    • Hyperextension of the head to improve airflow
  • Esophageal constriction: dysphagia, choking, retching, vomiting

Diagnostics

  • Chest x-ray (anteroposterior and lateral): shows anterior tracheal bowing and narrowing
  • MRI scan of the thorax: imaging method of choice; visualization of the defect

Treatment

  • Surgical division of the minor arch

References:[27][28][29][30]