• Clinical science

Acyanotic congenital heart defects

Abstract


Acyanotic heart defects are congenital cardiac malformations that 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), or maternal consumption of drugs or alcohol during pregnancy. Acyanotic heart defects are characterized pathophysiologically by a left-to-right shunt, which causes pulmonary hypertension and right heart hypertrophy. The symptoms depend on the extent of the malformation and the resulting impairment of cardiac function. Infants may be asymptomatic or present with exercise intolerance, failure to thrive, and symptoms of heart failure. Characteristic heart murmurs are important clues for establishing the diagnosis, which is typically confirmed by visualizing the defect on echocardiography. A chest x-ray, MRI, or cardiac catheterization may also be required to determine the indications for surgery and plan the procedure. Acyanotic heart defects requiring treatment are repaired via catheter procedures or surgery. Supportive medical therapy is needed in cases of heart failure (e.g., diuretics, inotropic agents) or if surgery cannot be performed (e.g., prostaglandin). Common complications include arrhythmias, embolisms, and infective endocarditis, especially if treatment is delayed.

Pathophysiology

General pathophysiological processes

  • The left chambers of the heart are a high-pressure pump system and the right chambers of the heart are a low-pressure pump system.
  • Heart defects may lead to the formation of connections between the two systems (shunts), allowing blood to flow along the pressure gradient from high to low pressure.

Untreated left-to-right shunts (acyanotic heart defects) may progress to right-to-left shunts (cyanotic defects) if right ventricular pressure exceeds left ventricular pressure due to pulmonary arterial hypertension (Eisenmenger reaction).

References:[1]

Overview of acyanotic congenital heart defects

General clinical features

General treatment concepts

  • Administration of IV prostaglandin/PGE1 (e.g., alprostadil)
    • Indicated in ductal-dependent CHDs until surgery can be performed
    • Mechanism: prostaglandin prevents the ductus arteriosus from closing → creates intentional shunt to allow mixing of deoxygenated with oxygenated blood
Ductal dependent CHDs
PDA needed for systemic circulation PDA needed for pulmonary circulation

Critical aortic valve stenosis

Critical pulmonary valve stenosis

Coarctation of the aorta Tetralogy of Fallot
Transposition of the great arteries Tricuspid atresia
Hypoplastic left heart syndrome
  • In cases of heart failure
    • Decrease fluid volume and lower pulmonary vascular resistance: diuretics or ACE-I inhibitors
    • Inotropic agents to improve contractility of the heart (e.g., digoxin)
  • Antibiotic prophylaxis; : not generally recommended before procedures; given for 6 months after surgical correction procedures and if small defects remain after repair
  • Nutritional support and immunoprophylaxis
  • If the Eisenmenger reaction has occurred: heart-lung transplant or lung transplant

The “3 Ds” of acyanotic CHDs: VSD, ASD, PDA.
References:[2][3][4][5][6][7][8][9]

Atrial septal defect (ASD)

Epidemiology

Etiology

Pathophysiology

Clinical findings

  • Depend on defect size and shunt volume
    • Small defects: usually asymptomatic
    • Large defects
      • See “Nonspecific symptoms” and “Heart failure” in the overview above.
      • Palpitations
      • ASDs typically manifest with advancing age.
  • Auscultation

Diagnostics

Treatment

  • In childhood, spontaneous closure may occur.
  • Patch repair
    • Indicated in symptomatic children with significant left-to-right shunt
    • Surgical or via percutaneous transcatheter procedure

Complications

References:[2][10][11][12][13][14][15]

Ventricular septal defect (VSD)

Epidemiology

  • The most common congenital heart defect (4/1000 live births)
  • Occurs as an isolated heart defect or in combination with others

Etiology

Pathophysiology

Clinical findings

  • Small defects: usually asymptomatic
  • Medium-sized or large defects
    • Lead to cardiac failure in the first 2–3 months of life
      • Some VSDs can present after the first weeks of life because pulmonary vascular resistance (PVR) is high at birth and decreases thereafter. PVR↓ right ventricular pressure → left-to-right shunt → presence of symptoms
    • See also “Nonspecific symptoms” and “Heart failure” in the overview section above.
  • Palpation: Hyperdynamic precordium may be detected in hemodynamically relevant defects.
  • Auscultatory findings
    • Harsh holosystolic murmur over the left lower sternal border; typically louder in small defects
    • Mid-diastolic murmur over cardiac apex
    • Systolic thrill
    • Loud pulmonic S2; (if pulmonary hypertension develops)

Diagnostics

  • Doppler echocardiography: confirms diagnosis; evaluation of defect size and shunt volume; exclusion of other anomalies
  • ECG: signs of right heart hypertrophy
  • Chest x-ray
    • Enhanced pulmonary vascular markings
    • Left atrial and ventricular enlargement
    • In later stages, enlarged right ventricle and pulmonary artery (due to elevated PVR)

Treatment

  • Small VSDs: rarely require surgical interventions → small to moderate defects often heal spontaneously; follow-up echocardiography recommended
  • Symptomatic and large VSDs
    • See treatment of “Heart failure” in the overview section above.
    • Surgical (patch) repair in children < 1 year of age with signs of pulmonary hypertension and older children who did not improve with medical therapy
      • Closure of a VSD results in a decrease in right ventricular and left atrial pressures and an increase in left ventricular pressure when compared to pre-treatment values
    • Heart-lung transplant or lung transplant with concurrent VSD repair if Eisenmenger's reaction has occurred

Complications

References:[2][3][16][17][18][19]

Patent foramen ovale (PFO)

Definition

  • Persistence of the foramen ovale beyond 1 year of age

Epidemiology

Pathophysiology

  • The foramen ovale in the atrial septum does not close after birth. mild left-to-right shunt
  • A shunt reversal may be induced by certain maneuvers that induce an increase in right atrial pressure (e.g., Valsalva maneuver, coughing).

Clinical findings

  • Patients are usually asymptomatic until complications occur (see below).

Diagnostics

Complications

Treatment

  • Asymptomatic PFO: The majority of cases do not require any treatment.
  • Ischemic infarction in patients with confirmed PFO; : medical therapy with antiplatelet agents; or anticoagulation; and surgical or percutaneous closure of the defect

References:[20][21]

Pulmonary valve stenosis

Pathophysiology

  • Stenosis leads to obstruction of the right ventricular outflow tract, resulting in pressure overload and right ventricular hypertrophy.

Clinical findings

  • Depending on the grade of stenosis, symptoms of heart failure may occur.
  • Systolic murmur with point of maximal intensity over the second left ICS, sternal border

Diagnostics

Treatment

  • Transcatheter dilatation of the pulmonary valve
    • Indication: prestenotic to poststenotic pressure gradient > 50 mm Hg
    • Technique: balloon pulmonary valvuloplasty
  • Surgical commissurotomy: if balloon dilatation is not possible

References:[1]

Patent ductus arteriosus (PDA)

Definition

Epidemiology

  • Sex: > (2:1)

Etiology

Pathophysiology

Clinical features

  • Small PDA: asymptomatic with normal findings on physical examination
  • Large PDA
    • Nonspecific symptoms (e.g., failure to thrive; ) and symptoms of heart failure in infancy (see overview section above)
    • Physical examination
      • Heaving, laterally displaced apical impulse
      • Bounding peripheral pulses; , wide pulse pressure (pulsus celer et altus)
      • Auscultatory findings: loud continuous murmur (“machinery” murmur); ; best heard in the left infraclavicular region (Gibson's area)

Diagnostics

  • Echocardiography (confirmatory test)
    • Shows left cardiac enlargement (in larger PDAs)
    • Doppler: assesses degree of shunt and pulmonary artery pressure
    • Color Doppler: demonstrates blood flow from the aorta into the pulmonary artery
  • ECG: : normal in small PDA; left axis deviation due to LVH in large PDA
  • Chest x-ray: prominent pulmonary artery and aortic knob along upper left heart border; increased pulmonary markings
  • Cardiac catheterization and angiography: only necessary prior to repair or in more complex CHDs

Treatment

  • Observation: Regular evaluation of the heart and pulmonary vasculature is indicated in patients with a small PDA without evidence of left-sided heart volume overload.
  • Elective ductal closure

Complications

References:[2][3][22][23][24][25]

Coarctation of the aorta

Definition

Epidemiology

  • Prevalence: 4/10,000 live births
  • Sex: >
  • Usually associated with bicuspid aortic valve , VSD, and/or PDA

Etiology

Pathophysiology

  • Genetic defects and/or intrauterine ischemia → medial thickening and intimal hyperplasia form a ridge encircling the aortic lumen → narrowing of the aorta → ↑ flow proximal and ↓ flow distal to the narrowing
  • Compensatory mechanisms
    • Myocardial hypertrophy and collateral blood flow (e.g., intercostal vessels , scapular vessels) develop in cases of discrete stenosis to compensate for the left ventricular outflow tract obstruction (common) → onset of symptoms usually later in childhood
    • In long segment stenosis, there is no time for development of compensatory mechanisms → closure of PDA after birth → left ventricular pressure and volume overload → hypoperfusion of organs and extremities distal to the stenosis, heart failure, cardiogenic shock

Clinical findings

  • Newborns
  • Childhood
    • Chest pain, cold feet, and lower-extremity claudication on physical exertion
    • ↑ BP in upper extremities and ↓ BP in lower extremities
    • Auscultation: systolic ejection murmur over left paravertebral region and/or continuous murmur below left clavicula and between the shoulder blades ; systolic click in case of bicuspid aortic valve
    • Palpation of strong displaced apical impulse to the left
  • Adults

Diagnostics

  • Best initial test: upper and lower extremity blood pressure measurement and search for brachial-femoral delay
  • Pulse oximetry: ↓ SpO2
  • Echocardiography with doppler: (confirmatory test): location and extent of stenosis; concurrent anomalies
  • X-ray
    • Cardiomegaly and ↑ pulmonary vascular markings
    • “Figure of 3” sign
    • Rib notching (on inferior border of the 3rd– 8th ribs)
  • MRI or CT: in complicated cases and in adults; determine length of coarctation, intervention planning
  • Genetic testing for Turner syndrome

Treatment

  • Initial management: infusion of PGE1 (alprostadil)
  • Surgery
    • Should be performed as soon as possible in critical cases.
    • Indication: pressure gradient across the stenosis > 20 mm Hg
    • Techniques: surgical correction; or balloon angioplasty
  • Follow-up and monitor for restenosis, aortic aneurysm and aortic dissection

Complications

References:[2][26][27][28]

Endocardial cushion defect

Definition

Etiology

Pathophysiology

  • Complete form (ASD and VSD) → atrial and ventricular left-to-right shunt → excessive pulmonary blood flow and biventricular volume overloadpulmonary hypertension and heart failure
  • Partial form (only ASD) → atrial left-to-right shunt → symptoms may remain minimal until adulthood
  • In both forms: abnormal AV valveAV valve regurgitation → in severe cases, in utero heart failure (nonimmune hydrops fetalis)

Clinical features

  • Complete form: See “Nonspecific symptoms” and “Heart failure” in the overview section above.
  • Partial form: See “Clinical features” of ASD.
  • Heart murmurs according to underlying characteristic septal and valvular defects

Diagnostics

Treatment

  • Improve cardiac function in patients with heart failure (see treatment of “Heart failure symptoms” in the overview section above)
  • Surgical repair

References:[3][29][30]