Ventricular Septal Defect

Introduction

A Ventral Septal Defect (VSD) is a defect in the ventricular septum that allows shunting of blood between the ventricles.  The direction of the shunt depends on the relative pressures between the two systems (pulmonic and systemic). 

Vsd simple-lg.jpg
Illustration showing various forms of ventricular septal defects.
1. Conoventricular, malaligned, 2. Perimembranous, 3. Inlet, 4. Muscular
https://en.wikipedia.org/wiki/Ventricular_septal_defect

 When pulmonary vascular resistance is low, the shunt is left-to-right but eventually reverses to right-to-left as pulmonary hypertension develops (Eisenmenger syndrome).         

Eyzenmenger sindromu.jpg
Schematic drawing showing the principles of Eisenmenger's syndrome
https://en.wikipedia.org/wiki/Eisenmenger%27s_syndrome

 Prevalence:  

VSDs are the most common congenital heart defect and account for ~50% of all congenital heart disease at a rate of 41.8/10,000 live births.  They occur in isolation or as part of a combination of symptoms such as in tetralogy of Fallot.
 

Anatomy/Embryology:  

VSDs are classified as either membranous, subpulmonic, AV canal, or muscular defects.  Both membranous and AV canal are susceptible to heart block either spontaneously or from surgery due to their proximity to the bundle of His. 

  • Membranous: the most common (75%). Lie just beneath the aortic valve and can extend into the muscular septum. Complications include aortic valve obstruction, coarctation of the aorta.
  • Subpulmonic: more common in Asian populations. Lie just beneath the two arterial trunks. 
  • AV canal: posterior and superior to the tricuspid valve. Usually associated with an ASD as part of a complete endocardial cushion defect.
  • Muscular: usually close spontaneously. Can present with multiple defects ("Swiss cheese" septum) that functionally acts as one large defect.


www.revespcardiol.org/en/percutaneous-intervention-in-adult-congenital/a...

 Associated conditions:

Tetralogy of Fallot, transposition of the great arteries, subaortic stenosis, coarction of the aorta.

tetr_0_0.JPG
https://en.wikipedia.org/wiki/Tetralogy_of_Fallot

 Presentation:

Typically presents during the neonatal period on a range from an isolated murmur to severe heart failure.  Symptoms become apparent when the pulmonary vascular resistance declines to allow left-to-right shunting. 

Common presenting signs and symptoms include:

  • Tachypnea & increased work of breathing
  • Tachycardia
  • Poor weight gain / FTT
  • Diaphoresis
  • Pulmonary rales if heart failure marked.

Physical findings:                                            

  1. Constitutional: Poor weight gain 
  2. Palpation: A thrill in the 3rd or 4th intercostal space in patients with small VSDs and large pressure differentials.  Prominent apical impulse due to increased LV output to compensate for left-to-right shunt.  Apex is laterally displaced as heart enlarges.
  3. Auscultation:                                   Click for Audio Example
          
    1. Systolic murmur: 3/6 low pitched, harsh holosystolic murmur best heard at lower sternal border in small defects; a 2/6 or louder, high pitched holsystolic murmur in moderate sized defects; and in large defects the murmur may disappear as pulmonary vascular resistance reaches systemic levels.
    • A smaller defect will lead to a louder murmur
    1. Diastolic murmur: Diastolic rumble due to increased flow across mitral valve due to left-to right shunting.

CXR:  

Increased pulmonary vascular markings.  Left atrium, left ventricle, and pulmonary artery may all be enlarged. 

ECG: 

ekg_0_0_0.jpg
Left ventricular hypertrophy demonstrated by tall R in V5, V6.
http://en.ecgpedia.org/wiki/Chamber_Hypertrophy_and _Enlargement

Cardiac Catheterization:

Rarely performed, usually used to determine the need for closure

  • Pulmonic:systemic flow ratio (Qp/Qs) helps determine the need for closure. 
  • If PA pressure is normal, no indication for closing
  • Testing of vasodilators and measurement of pulmonary vascular resistance for perioperative management

Complications:

  1. Heart failure
  2. Infective endocarditis
  3. Pulmonary hypertension and resultant Eisenmenger syndrome
  4. Thromboembolic complications

Prognosis:  

25% of VSDs will close spontaneously by 2 years of life.  94.6% of patients with small, hemodynamically uncomplicated VSDs in childhood will be asymptomatic in adulthood.  For patients with Eisenmenger syndrome, the 20 year survival rate was 54%.

Treatment: 

  1. Surgical or transcutaneous device closure.  Closure not recommended in patients with irreversible pulmonary arterial hypertension (Eisenmenger syndrome).
    • Indications for closure: pulmonary-to-systemic blood flow ratio (Qp/Qs) ≥ 2:1 with evidence of left ventricular volume overload, symptomatic, pulmonary artery pressure >50 mm Hg.
  2.  Medical therapy in patients with Eisenmenger syndrome
    • Pulmonary vasodilator therapy (Nitric oxide)

Treatment prognosis:  

25% of VSDs will close spontaneously by 2 years of life.

References

  1. Frontera-Izquierdo, P., and Cabezuelo-Huerta, G. (1992). Natural and modified history of isolated ventricular septal defect: a 17-year study. Pediatr Cardiol, 13(4), 193-197.
  2. Penny, D.J., and Vick, G.W. (2011). Ventricular septal defect. Lancet, 377, 1103-1112.
  3. Wu, M., et. al. (2006). Ventricular septal defect with secondary left ventricular-to-right atrial shunt is associated with a higher risk for infective endocarditis and a lower late chance of closure. Pediatrics, 117(2), 262-267.