• Clinical science

Cyanotic congenital heart defects

Abstract

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)
  • 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 ; single second heart sound

Diagnostics

  • Pulse oximetry: ↓ SpO2
  • Hyperoxia test: to distinguish cardiac from pulmonary causes of cyanosis
  • ECG: right axis with right heart hypertrophy; P pulmonale with increasing age
  • Imaging
    • Echocardiography: detection of the main features of TOF, quantification of right ventricular outflow tract pressure gradient (supplementary cardiac catheterization may be performed)
    • Chest x-ray: : absent pulmonary artery segment, decreased pulmonary vasculature, small boot-shapedheart

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

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

Transposition of the great vessels (TGV)

Definition

  • Anatomical reversal of the aorta and the pulmonary artery

Epidemiology

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

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

  • Initially: infusion of prostaglandin (PGE1) to prevent closure of the PDA
  • Definite repair: surgical correction within the first two weeks of life with arterial switch procedure
  • Balloon atrial septostomy
    • Indications: if surgery cannot be performed or if hypoxia is severe despite IV PGE1 administration prior to surgery
    • Procedure: right heart catheterization with creation or enlargement of an existing ASD

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



References:[1][2][9][10][11][12][13]

Hypoplastic left heart syndrome

Definition

Epidemiology

Etiology

Pathophysiology

Clinical findings

Diagnostics

Treatment

  • Initially: continuous infusion of PGE1 prior to heart surgery
  • Definite therapy
    • Staged surgical correction in three steps (Norwood, Glenn, and Fontan procedure)
    • Alternative: heart transplant

Prognosis

  • Most children reach adult age.

Without treatment, 95% of patients with hypoplastic left heart syndrome die within their first month of life!
References:[14]

Tricuspid valve atresia

Definition

Epidemiology

  • Third most common cyanotic heart defect
  • Almost always accompanied by ASD, VSD, and right ventricular hypoplasia

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)
  • Optional temporary measures
    • In cases with concurrent pulmonary valve atresia or severe stenosis: systemic-to-pulmonary shunt to improve perfusion
    • Risk of pulmonary hypertension: pulmonary artery banding to control pulmonary hyperperfusion
  • 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][15][16]

Total anomalous pulmonary venous return

Definition

Epidemiology

  • 5th most common cause of cyanotic CHD

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][17]

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 septation; right 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.
    • Neonates with severe hypoxia who are dependent on prostaglandins:
      • Aortopulmonary shunt alone
      • Repair of the tricuspid valve
      • Surgical patch closure of the tricuspid valve, atrial septectomy, and placement of the aortopulmonary shunt with eventual single ventricular repair using the Fontan procedure
    • Following valve repair, TR and volume overload on the right ventricle may still be present. → Glenn shunt to reduce right ventricular load might be required.
  • Treatment of supraventricular tachyarrhythmias : cardiac ablation of the aberrant pathway

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

References:[18][1][1][19][2][20][21][22][23][24]

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][25]

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!
  • 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:[26]

Hemodynamically relevant coronary artery anomalies