Description

• A ventricular septal defect (VSD) is an opening in the ventricular septum, resulting in a communication between the left ventricle (LV) and the right ventricle (RV). The ventricular septum can be divided into four major areas:
  • Inlet/canal septum
  • Membranous/conoventricular septum
  • Muscular septum (largest)
  • Conal/infundibular/outlet septum (includes conal septal hypoplasia and malalignment types)
• There are several corresponding types of VSDs that have different natural histories and associated problems:
  • Inlet/canal VSDs: usually part of an atrioventricular (AV) canal defect, 5–7% of all VSDs
  • Membranous/conoventricular VSDs: 80% of all VSDs by classic teaching; fewer than muscular VSDs by echocardiographic data
  • Muscular VSDs: usually single and small but can be multiple and of variable size; 5–20% of all VSDs by classic teaching, but a large percentage are inaudible
  • Conal septal hypoplasia/outlet VSDs: usually large and unrestrictive; associated with aortic valve (AoV) cusp prolapse and aortic insufficiency
  • Anterior malalignment VSDs: usually associated with RV outflow tract obstruction; paradigms: tetralogy of Fallot, double outlet RV
  • Posterior malalignment VSDs: usually associated with LV outflow tract obstruction; paradigms: subaortic stenosis with coarctation or interrupted aortic arch
• There may also be multiple VSDs of different types in a single patient. Many complex forms of congenital heart disease include a VSD.

Epidemiology

• VSDs are the most common form of congenital heart disease, occurring in ~1.5 to 5.7 per 1,000 term births and ~4.5 to 7 per 1,000 preterm births, by classic teaching.
• Echocardiographic data show a higher incidence of ~50 per 1,000 live births, mostly asymptomatic muscular VSDs.

Risk Factors

Pathophysiology

• Both the size of the VSD and the ratio of pulmonary (PVR) to systemic vascular resistance (SVR) determine the direction and amount of shunting.
  • Small VSD: The VSD imposes high resistance to flow with a large LV-to-RV pressure gradient, usually resulting in normal RV pressures. The restrictive size results in a small left-to-right shunt. The VSD size is usually ≤1/4 the size of the AoV annulus. The workload of the ventricles is normal.
  • Moderate VSD: The VSD imposes modest resistance to flow, usually resulting in mildly elevated RV pressures. The amount of shunting can still be large and is determined by the PVR/SVR ratio. The VSD size is usually 1/3 to 2/3 the size of the AoV annulus. The workload of the ventricles is increased.
  • Large VSD: The VSD imposes no resistance to flow and is unrestrictive, resulting in systemic RV pressures and RV hypertension. The workload of the ventricles is markedly increased.
• The lower the PVR/SVR ratio, the greater the degree of left-to-right shunting. A large left-to-right shunt leads to pulmonary vascular congestion, tachypnea, tachycardia, and hepatomegaly, all signs of congestive heart failure (CHF). The amount of CHF correlates directly with shunt size and usually peaks at 6 to 8 weeks of age, timed with the nadir of PVR and physiologic anemia. Lack of significant CHF in patients with a large VSD signifies elevated PVR and requires careful evaluation. Cardiac catheterization may be required in these patients to provide additional data.
• If a large VSD is left untreated, pulmonary vascular obstructive disease will eventually develop, leading to reversal of the shunt, cyanosis, and RV failure (Eisenmenger syndrome).

History

• Small VSD: The child is usually asymptomatic, with normal growth and development. Most commonly, a murmur is detected at 1 to 6 weeks of age.
• Moderate VSD: The child is usually symptomatic with slow weight gain and sparing of longitudinal growth. There is often an increased incidence of respiratory infections. Sweating and fatigue with feeding may be present.
• Large VSD: The child is usually quite symptomatic, especially with a larger shunt, showing signs of CHF, and marked failure to thrive.
• Children with Eisenmenger syndrome have cyanosis, fatigue, and symptoms of right heart failure.

Physical Exam

• Small VSD
  • The child usually appears healthy with normal growth.
  • The heart action is quiet, but there is often an associated systolic thrill along the left sternal border with a membranous VSD, in contrast to a small muscular VSD.
  • Heart sounds are normal. A high-frequency, pansystolic murmur is present in membranous VSDs, whereas in muscular VSDs the murmur is not pansystolic.
  • The murmur is loudest over the region of the VSD.
• Moderate VSD
  • The child usually appears in mild distress with tachycardia and tachypnea.
  • The heart action is increased, and there is often still an associated thrill.
  • The P₂ component of S₂ may be normal or accentuated.
  • A medium frequency, pansystolic murmur is present over the location of the VSD.
  • A mid-diastolic rumble is present over the mitral listening area (apex), as a result of a significant shunt and indicates ≥2:1 pulmonary to systemic flow ratio. Hepatomegaly may be present.
• Large VSD
  • The child usually appears ill with marked distress and marked tachycardia and tachypnea, proportional to the size of the left-to-right shunt.
  • The heart action is markedly increased without a thrill. The P₂ component of S₂ is loud and narrowly split as a result of pulmonary hypertension.
  • A soft, low-frequency pansystolic murmur is present over the VSD.
  • The loudness of the mid-diastolic rumble is proportional to the size of the left-to-right shunt.
  • CHF physical exam signs are proportional to the size of the left-to-right shunt but are usually present to a significant degree.
• If significant aortic insufficiency develops, a high-frequency, early diastolic murmur is heard along the left sternal border.
• In newborns whose PVR has not yet fallen, the increased heart action remains the key to diagnosis as auscultation may be unimpressive.
• Likewise, in children with elevated PVR, the increased heart action remains the key to diagnosis. Auscultation shows a narrowly split S₂ with a loud P₂. The murmur loudness is dependent on VSD size and shunt but often is soft or absent and unimpressive.
• Once Eisenmenger syndrome develops (secondary to pulmonary vascular obstructive changes), patients manifest cyanosis, clubbing, an increased RV impulse, a narrowly split S₂ with a loud P₂ component, and a soft or absent VSD murmur. There may be a systolic murmur of tricuspid insufficiency at the left lower sternal border (LLSB), a high-frequency early diastolic murmur of pulmonary insufficiency, or an S3 at the LLSB. There is usually associated jugular venous distention and hepatomegaly, indicating high right-sided filling pressures.

Diagnostic Tests and Interpretation

General Measures

• Small VSD: no intervention; continued observation
• Moderate VSD: If signs of CHF develop, digoxin, diuretics, afterload reduction, and increased caloric intake are indicated.
• Large VSD: CHF often develops and requires aggressive therapy as noted above.
• Membranous and muscular VSDs often become smaller or close spontaneously. Generally, observation and/or medical therapy is indicated for a few months.
• Conoseptal hypoplasia and malalignment VSDs do not close spontaneously and therefore require surgical closure.
• After 1 year of life, a significant left-to-right shunt (Qp:Qs ≥2:1) or elevated pulmonary artery pressures are an indication for surgery.
• Children with elevated pulmonary artery pressures (≥1/2 systemic) should undergo repair before 2 years of age, even if CHF symptoms are controlled.
• Development of complications, including aortic insufficiency, subaortic membrane, and double-chamber RV, is usually an indication for surgical repair.
• Surgical correction may be contraindicated if the PVR is >8 Wood units/m².
• Recent series of surgical VSD closure report a mortality of <2%.
• Complete heart block occurs in <2% of patients postoperatively but requires pacemaker therapy when it occurs.
• A small percentage of patients with muscular or membranous VSDs may have successful transcatheter device closure.

Prognosis

• Spontaneous closure: usually by age 2 years; 90% of small muscular VSDs and 8–35% of small conoventricular/membranous VSDs
• Prognosis with surgical closure is excellent.
• The risk of Eisenmenger syndrome is considered minimal if large VSDs are surgically closed by 2 years of age.
• Caveat: Despite timely VSD surgical closure, a tiny percentage of patients still go on to develop Eisenmenger syndrome.

Complications

• All VSDs: endocarditis—overall rate of 15 cases per 10,000 person-years of follow-up
• Moderate-to-large VSDs: LV volume overload, left atrial hypertension, CHF, poor growth, Eisenmenger syndrome
• Specific types:
  • Inlet/canal VSDs: often associated with cleft mitral valve with possible AV valve insufficiency
  • Membranous/conoventricular VSDs: risk for development of aortic insufficiency typically due to prolapse of the right aortic cusp, subaortic membrane, or double-chamber RV
  • Muscular VSDs: isolated—near-zero risk for the development of subsequent lesions
  • Conal septal hypoplasia VSDs: risk for development of aortic insufficiency
  • Malalignment VSDs: usually associated with outflow tract obstruction and distal great artery hypoplasia/obstruction

Follow-Up Recommendations

ICD-9

• 745.4 Ventricular septal defect
• 746.89 Other specified congenital anomalies of heart

ICD-10

• Q21.0 Ventricular septal defect
• Q24.8 Other specified congenital malformations of heart

SNOMED

• 30288003 Ventricular septal defect (disorder)
• 448923002 Hypoplasia of infundibular septum (disorder)