VSD

• Hole or defect between the RV and LV.
• Previously not treatable, now very treatable w/high likelihood of excellent outcome.
• May occur in isolation or as a part of a complex cardiac malformation.
• May be single or multiple defects.
• Estimated that 56 per 1000 births have a VSD.
• Some spontaneously close (75% of small 10% of large) -24% by 18 months, 50% by age 4, 75% by age 10.
• A normal ventricular septum will be smooth walled and sparsely trabeculated .
• Large defects : Qp:Qs >3.
• Small, pressure restrictive defects: Qp:Qs <2.
• Usually left to right shunt unless PHTN is present.
• Small VSDs can become complicated by infective endocarditis.

Symptoms of VSDs

• Large shunts result in pulmonary edema and tachypnea.
• Large defects can: interfere w/child’s feeding and growth, rapid breathing, excessive sweating, poor weight gain.
• Smaller defects can cause little or no hemodynamic effects.

VSD Sizes

• Size of defect is compared to aortic annulus.
• Small: <50% of Annulus.
• Moderate is 50-100%.
• Large is > 100%. 

Types of VSDs

• Membranous
• Muscular
• Inlet
• Outlet 

Are VSDs isolated?

• Nearly half of patients with VSD’s have: PDA, ASD’s, Pulmonary Stenosis, LSVC, Double chambered RV or Subaortic stenosis.

VSD Murmur

• Holosystolic at left lower sternal border

• Smaller defects have high pitched murmurs

• Restrictive VSDs will have velocities as high as 4m/s or higher.

Membranous VSD

• Accounts for 80% of VSDs .

Muscular VSD

• Also called: trabecular.
• Classified: Anterior muscular, Mid muscular, Apical muscular, Posterior muscular.
• Large trabecular (muscular) VSD’s can be clearly defined on the LV side .
• On RV side the defect may have the appearance of multiple defects because of the trabeculations (swiss cheese septum).
• The conduction system is located remotely from the borders of the muscular defects.
• Can be acquired after trauma or myocardial infarction.
•  Location: Can extend from the attachment of the TV leaflets towards the cardiac apex.

Inlet VSD

• The septum between the tricuspid annulus and the insertion of papillary muscles is deficient.
• Located posteriorly and inferiorly beneath the TV leaflets. 
• May be associated with straddling chordae and papillary muscle attachments of septal leaflets of TV across the VSD into the LV.
• Hearts with straddling TV may have mal-alignment between interatrial and interventricle septum.
• May have different degrees of RV hypoplasia. 
•  AV node lies more laterally and anteriorly than normal.
• Bundle of His courses along the posterior, inferior margins of inlet VSD’s on the LV side.

Outlet VSD

• Also called: Infundibular, Conal, Supracrystal, Sub pulmonary, Sub arterial.
• Usually occurs in isolation.
• Located anterior to membranous septum, above trabecular septum, below pulmonary valve (12-3 SAX).
• Ao valve and pulmonary valve lie at the same level because of the absence of part of the septum.
• Associated with AI: right coronary cusp prolapsed.
• Prevalent in the Asian population. 

Malalignment VSD

• Defect that lies between the outlet and trabecular septum.
•  Seen in the setting of more complex CHD: tetrology of fallot (TOF), truncus arteriosus, interrupted aortic arch.

• Malalignment anterior and leftward: the "floor" of the RV outflow tract is elevated and results in sub pulmonary obstruction.

• Malalignment posterior and rightward: the "roof" of the LV outflow tract is lowered and results in sub aortic stenosis.

   

   

Hemodynamics of VSDs 

• Systole blood flows across the defect into the RV, through PV and into the pulmonary bed. It returns to the LA and LV and some recirculates through the lungs.
• Both ventricles carry a volume overload (LVE, RVE, dilated PA).
• LA will also dilate.

Effects of Long-term VSDs

Surgical Repair of VSDs

• Surgical repair of membraneous VSDs are difficult because the AV conduction bundle, branching bundle and left bundle branches lies along the posterior-inferior border of the defect.
• Muscular defects can be closed by patch or device.
• Pulmonary Artery Banding in small/frail infants where the pulmonary flow is restricted by constricting the PA with a strong ligature. This helps drop the pressure distal to the band to about 30mmHg.

VSDs and Echo Goal

• Confirm VSD.
• Determine size and site of VSD.
• R/O associated lesions.
• Estimate RV and PA pressure.

VSDs and Echo Method

• Interrogate entire septum with Color from PLAX, PSAX, apical and subcostal views.
• Record and measure VSD, assess alignment. 
• Record blood pressure.
• Record VSD velocity from at least 2 views.
• Assess PA velocities.
• Record infundibular region.
• Especially for PM VSD. Look at RVOT to see if a membrane is forming (10% of the time)=> DCRV (Double Chambered RV or behave like TOF).
• Record LV and LA from all views.
• R/O subaortic membranes and associated lesions (e.g. coarctation).
• Assess for AI if there is malalignment (or if VSD is anterior). Commonly develop non-support of right cusp and AI. AI may be into RV, LV, or both.

Post-op VSD

• Assess integrity of patch.
• Evaluate Function. 
• R/O Effusion.

RVSP

• RVSP= Systolic BP-4v^2

Example: BP: 124/70     Vvsd: 4m/s

124-4(4)^2= 124-64=60

Qp:Qs

.785(R)^2*r:.785(L)^2*t

R= diameter of RVOT: 3cm           R^2*r:L^2*t

r= VTI RVOT: 20cm                      3^2*20:2^2*15

L= diameter of LVOT: 2cm             180:60

t= VTI LVOT: 15cm                          3:1