• 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

  • Heart defects may lead to the formation of connections between the right and the left heart (see “Pathophysiology” in acyanotic congenital heart defects).
    • Right-to-left shunt: blood flows from the right to the left heart via a shunt → deoxygenated blood enters the systemic circulation → cyanosis

General clinical features

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

  • Severe RVOT: IV prostaglandin (PGE1) until surgery
  • Acute hypoxia (tet spells)
    • Administer oxygen
    • Knee to chest position, squatting
    • IV morphine for sedation and fluids
    • If above measures fail: IV beta blockers
  • Heart failure: See “Treatment” in “Overview” section above.
  • Long-term management
    • Surgery: performed within the first year of life, if possible
    • Follow-up care: to prevent long-term complications such as heart failure, arrhythmias, and neurodevelopmental impairment

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

Transposition of the great vessels (TGV)

Definition

Epidemiology

  • Accounts for ∼ 20 % of all cyanotic CHD
  • Often associated with VSD, left ventricular outlet obstruction, and abnormal valves and coronary arteries

Etiology

Pathophysiology

  • Failed spiraling of the aorticopulmonary septumpulmonary circulation and systemic circulation function as completely separate parallel circuits → oxygenated blood cannot pass into systemic circulation → incompatible with life unless mixing occurs via an intracardiac shunt across a PFO, VSD, or ASD or via an extracardiac connection (e.g., PDA)

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

  • Initially: continuous infusion of PGE1 prior to heart surgery
  • Definite therapy

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

  • Initially: infusion of prostaglandin (PGE1)
  • Definitive treatment: three-staged surgical procedure to separate the pulmonary and systemic circulation

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

  • The four pulmonary veins drain abnormally into the systemic venous circulation (most commonly the left brachiocephalic vein) instead of the left atrium.
  • Oxygenated pulmonary venous return mixes with the systemic venous system → partially oxygenated blood is shunted right-to-left through an ASD, PFO, or PDA into the systemic arterial circulation cyanosis

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

  • Malformed and displaced tricuspid valve leaflets causing tricuspid valve regurgitation and right heart enlargement

Epidemiology

Etiology

  • Prenatal lithium exposure
  • Isolated genetic defects

Pathophysiology

  • Incomplete undermining process during cardiac septationright AV valve does not separate normally from the ventricular myocardium
  • Displaced valve reduces the ventricular volume → regurgitation into the right atrium (tricuspid regurgitation) → atrial dilatation; poorly functioning, small RV (atrialization of the right ventricle); functional pulmonary valve atresia; ; obstruction of the RV outflow by the large, sail-like anterior leaflet → blood flows through the patent foramen ovale (right-to-left shunt) → cyanosis

Clinical findings

Diagnostics

Treatment

  • IV PGE1: : in infants with acute symptoms of heart failure
  • Surgery
    • Indication is individually assessed based on the cardiac function and severity of symptoms.
    • Surgery typically occurs in stages and involves the creation of a systemic-pulmonary shunt, repair of the tricuspid valve, and reconstruction of the right ventricle.

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

  • Rare, but accounts for 4% of all critical CHD cases
  • Often associated with VSD, PDA, coronary artery anomalies

Etiology

Clinical features

  • Cyanosis
  • Symptoms of heart failure
  • Accentuated and bounding peripheral pulses
  • Harsh systolic murmur at lower left sternal border, loud S2

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]