• Clinical science

Acyanotic congenital heart defects

Summary

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 use of drugs or alcohol during pregnancy. Acyanotic heart defects are pathophysiologically characterized 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. Chest x-ray, MRI, or cardiac catheterization may also be required to determine indications for surgery and plan the procedure. Acyanotic 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). Common complications include arrhythmias, embolisms, and infective endocarditis, especially if treatment is delayed.

Overview

General pathophysiological processes [1]

Pulmonary arterial hypertension (Eisenmenger syndrome) may cause untreated left-to-right shunts (acyanotic heart defects) to progress to right-to-left shunts (cyanotic defects) if right ventricular pressure exceeds left ventricular pressure.

Left-to-Right shunts = LateR cyanosis. Right-to-Left shunts = eaRLy cyanosis.

General clinical features

For specific features, see “Clinical features” in the subsections below.

General treatment considerations

The “3 Ds” of acyanotic CHDs (in order of frequency): VSD, ASD, PDA

Ventricular septal defect (VSD)

Epidemiology

  • The most common congenital heart defect (∼ 4/1,000 live births) [6]
  • Occurs as an isolated heart defect or in combination with others (e.g., with AVSD, tetralogy of Fallot, TGA)

Etiology

Pathophysiology

Clinical features [7]

  • Small defects: usually asymptomatic
  • Medium-sized or large defects
    • Lead to heart failure by the age of 2–3 months
    • Become symptomatic after high pulmonary vascular resistance (PVR) present at birth starts to decrease: PVR ↓ right ventricular pressure → left-to-right shunt symptoms
    • See “Nonspecific findings” and “Heart failure” in “Overview” above.
  • Hyperdynamic precordium may be detected in hemodynamically relevant defects.
  • Harsh holosystolic murmur over the left lower sternal border
    • Becomes more intense with maneuvers that increase left ventricular afterload (e.g., handgrip)
    • Typically louder in small defects
  • Mid-diastolic murmur over cardiac apex
  • Systolic thrill
  • Loud pulmonic S2 (if pulmonary hypertension develops)

Symptoms of heart failure in children with VSD only develop when PVR decreases to adult levels and thus allows left-to-right shunting to occur.

Diagnostics [7]

Treatment [7][5]

  • Small defects often heal spontaneously and rarely require surgical interventions (follow-up echocardiography is recommended)
  • Symptomatic and large defects

Complications

Atrial septal defect (ASD)

Epidemiology

  • Second most common CHD (∼ 2/1,000 live births)
  • Sex: >

Etiology

Pathophysiology

Clinical features

  • Depend on defect size and shunt volume
    • Small defects: usually asymptomatic
    • Medium-sized to large defects
      • Symptoms can vary from asymptomatic to heart failure.
      • ASDs typically manifest with advancing age. [8]
  • Systolic ejection murmur over the second left ICS sternal border
  • Widely split second heart sound (S2) over the second left ICS, which is fixed (does not change with respiration )
  • Soft mid-diastolic murmur over the lower left sternal border
  • See “General clinical features” above.

Diagnostics [9]

Treatment [10]

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

Complications [11]

Patent foramen ovale (PFO)

Epidemiology

Etiology

Pathophysiology

ASD = Septal tissue Deficiency. PFO = enough tissue, but Problems with Fusion.

Clinical features

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

Diagnostics

  • Often an incidental finding
  • If ischemic stroke occurs
    • Contrast echocardiography (best initial and confirmatory test): to evaluate defect size and shunt volume
    • Transesophageal echocardiography: if contrast echocardiography findings are negative

Treatment

Complications

PFO may not be causally related to stroke. Screening for DVT and other causes is still important.

Patent ductus arteriosus (PDA)

Definition

Epidemiology

Etiology

Pathophysiology

Clinical features

PDA comes with Prolonged Deafening Auscultation findings.

Diagnostics [14]

Treatment [15]

Complications [14]

Coarctation of the aorta

Definition

Epidemiology [16]

Etiology [17]

Pathophysiology [17]

Clinical features [17]

Diagnostics [17]

  • Blood pressure measurements
  • Pulse oximetry: SpO2
  • Doppler echocardiography (confirmatory test): location and extent of stenosis; detection of concurrent anomalies (VSD, PDA, bicuspid aortic valve)
  • X-ray
    • Cardiomegaly and ↑ pulmonary vascular markings
    • Figure of 3 sign: the result of an hourglass-like narrowing of the aorta caused by pre- and postdilatation of the aorta with an indentation at the site of coarctation
    • Rib notching: a radiographic sign caused by collateral circulation between the internal thoracic and intercostal arteries.
      • Enlarged vessels compress the neighboring ribs and lead to their pressure atrophy.
      • Classically affects the inferior border of the 3rd– 8th ribs
  • MRI or CT
    • In complicated cases and in adults
    • To determine the length of coarctation and for intervention planning
  • Genetic testing: for Turner syndrome

Treatment [21]

  • Initial management: infusion of prostaglandin (PGE1)
  • Surgical correction; or balloon angioplasty: for most patients < 5 years of age. Older patients may have a transcatheter intervention with stent placement.
  • Follow-up and monitor for restenosis, aortic aneurysm, and aortic dissection.

Complications

Endocardial cushion defect

Definition [23]

  • Defect of atrioventricular valves (i.e., mitral and tricuspid valves) as well as the atrial and/or ventricular septum
    • Complete form: ASD and VSD, common AV valve
    • Partial form: only ASD and minor AV valve abnormalities

Etiology

Pathophysiology [23]

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

Clinical features [23]

  • Complete form: See “Nonspecific findings” and “Heart failure” in “Overview” above.
  • Partial form: See “Clinical features” in “Atrial septal defect (ASD)“ above.

Diagnostics [23]

Treatment [26]

  • Improve cardiac function in patients with heart failure (see “General treatment considerations” for heart failure in “Overview” above).
  • Surgical repair

Pulmonary valve stenosis

Epidemiology

  • Relatively common in the general population (7–12% of all CHDs) [27]
  • Usually congenital (rarely acquired )

Pathophysiology

Clinical features

  • Depending on the grade of stenosis, symptoms of heart failure may occur.
  • Systolic murmur heard best over the second left ICS at the sternal border
  • S2 wide splitting

Diagnostics

Treatment

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