Ventricular Septal Defect

BASICS

DESCRIPTION

Ventricular septal defects (VSDs) are holes in the wall or septum which separates the left and right ventricles.

  • Can be single or multiple
  • May occur as isolated defects or part of more complex cardiac pathologies
  • Classified based on their location within the ventricular septum. There continues to be controversy regarding nomenclature.
    • Inlet (atrioventricular): often large, may involve abnormal attachments of the atrioventricular (tricuspid and mitral) valves
      • Can be associated with atrioventricular septal defects (AVSDs), a cardiac pathology often associated with Down syndrome
    • Membranous (perimembranous): result from a deficiency of the membranous portion of ventricular septum
      • Most common type
    • Muscular: within the musculature of the ventricular septum
      • Frequently multiple and can be located throughout the ventricular septum
      • Spontaneous closure with time is possible.
    • Outlet (infundibular, supracristal, subarterial, conoventricular): just beneath the aortic and pulmonary valves
      • Can be associated with semilunar valve prolapse and insufficiency
      • Most frequently associated with other defects such as Tetralogy of Fallot

EPIDEMIOLOGY

  • Most common type of congenital heart disease (CHD), accounting for approximately 25% of all cases of CHD
  • Incidence of 1.5 to 53.2 per 1,000 live births
  • Found in 0.3 per 1,000 adults
  • Range of genetic and environmental factors have been associated with VSDs.

RISK FACTORS

  • Prenatal risk factors
    • Maternal infection
    • Maternal diabetes mellitus
    • Phenylketonuria
  • Fetal exposure to alcohol, marijuana, cocaine, or medications such as metronidazole and ibuprofen

Genetics

  • 5% of VSDs are associated with chromosomal abnormalities, most commonly trisomy 13, 18, and 21.
  • Have also been linked to single-gene defects and polygenic mutations
  • Recurrence risk in an offspring with paternal VSD is 2%, and 6–10% with maternal VSDs.

PATHOPHYSIOLOGY

  • Clinical presentation largely influenced by the size of the defect and the pressure differential between the right and left ventricles.
  • Smaller perimembranous defects and those within the muscular ventricular septum often close on their own and are of no clinical significance.
  • Larger openings allow for shunting of the blood from the left to the right side of the heart across the ventricular septum as a result of the difference between systemic and pulmonary vascular resistance. This difference increases significantly after the 1st month of life as pulmonary vascular resistance drops.
  • The increased blood flow to the right side of the heart and resultant increased pressure in the right ventricle subsequently causes dilation of the pulmonary arteries, left atrium (LA), and left ventricle (LV).
  • Significant pulmonary over circulation caused by unrepaired, unrestrictive VSDs can lead to pulmonary vascular disease and pulmonary hypertension.
  • When pressure in the pulmonary vascular bed exceeds that of the systemic circulation, shunting across the ventricular septum can reverse and become right to left, a phenomenon known as Eisenmenger syndrome.

COMMONLY ASSOCIATED CONDITIONS

  • Tetralogy of Fallot
  • Double outlet right ventricle
  • Transposition of the great arteries
  • Atrioventricular canal defects

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