View TSDA Curriculum Online for this topic

2. Morphologic Classification
Perimembranous (80%)
Borders tricuspid valve
Conduction system posterior rim
Muscular (5%)
Borders all muscle
Frequently multiple
Conduction system remote
Doubly committed subarterial (10%)
Borders both semi-lunar valves
Inlet (5%)
A-V canal type
Posterior position
Conduction system posterior rim

3. Morphologic Classification
Perimembranous with
Inlet extension
Anterior extension
Outlet extension
Muscular
Outlet (conal)
Trabecular
Inlet
Anterior
Apical
Doubly committed subarterial
Inlet (A-V canal)

4. Malalignment Type
Relates to the alignment of trabecular to conal septum
Embryologic looping of the heart
Aorta seems displaced relative to VSD
Types
Anterior = TET
Posterior = Interrupted arch or coarct-VSD
Rotational = Taussig-Bing

5. Associated Lesions
Almost 50% with associated anomalies
Patent ductus arteriosus = 6%
25% in heart failure have PDA
Coarctation = 5-10%
Aortic stenosis = 2-3%
Subvalvular valvular

6. Pathophysiology
Shunting - Increased pulmonary flow
Greater flow through mitral valve = increased LV and RV work = LV hypertrophy and RV dilatation
Increased interstitial lung fluid
High pulmonary/low systemic flow = growth failure
Pulmonary vascular resistance increased
May develop Eisenmenger's syndrome and shunt reversal

7. Natural History
Spontaneous closure in majority
Pulmonary vascular resistance increases with age
Endocarditis rare - more in small or moderate VSD
9% mortality at 1 year with large VSD if untreated
Late deaths: Eisenmenger's 20 years
AI develops during first decade = 5%
Infundibular pulmonary stenosis = 5%

8. Clinical Symptoms
Heart failure, poor feeding, growth failure, tachypnea
Precordial pansystolic murmur, hyperactive heart
Apical diastolic murmur - large flow across mitral
If PVR SVR - clinical cyanosis

9. Diagnosis
Chest x-ray: Pulmonary vascularity, cardiomegaly, CHF
EKG: RVH, LVH
Echo: Very accurate
Cardiac catheterization: R and L heart studies, cineangiograms

10. Indications for Surgery
Large VSD
< 3 months - CHF (Qp:Qs2:1)
Elective repair at 6 months (PVR < 8.0 units)
Small VSD (Qp:Qs<2:1)
Endocarditis
Cardiac Enlargement
Any Aortic Incompetence
Subarterial (supracristal) VSD - any size

11. Principles of Repair
PDA present - ligate prior to CPB
Avoid conduction bundles
Close defect with patch
RA approach whenever possible

12. Surgical Approach
Perimembranous VSD - RA approach
Subarterial VSD - Pulmonary outflow tract or R ventriculotomy, aorta
" Swiss cheese " septum - May need LV incision
PA banding - Palliation in multiple VSD's
Transvenous closure with umbrella device or direct vision (experimental)

13. Risk Factors
Major associated anomalies
PDA, coarctation do NOT increase risk
Multiple VSD's - less of a factor in current era
Young age - not a factor unless major associated anomalies

14. Results
Premature death < 2.5% if PVR low preoperatively
Normal weight gain within 1 year
Complete heart block = 1%
Normal cardiac function if corrected < 2 years of age
Residual shunts requiring reoperation < 1-2%
Pulmonary hypertension - depends on preoperative PVR
The younger the age at repair, the better the chance of normal PVR post-operatively

1. Introduction
a) 1/1000 live births
b) Nearly 50% have additional major cardiovascular lesions (PDA, coarct, arch interruption)
c) First successful intracardiac closure - Lillehei, 1955, using cross-circulation

2. Anatomic classification
a) Divisions of interventricular septum
i) Membranous septum
ii) Outlet or conal septum
iii) Inlet septum or septum of atrioventricular (A-V) canal
iv) Muscular or trabecular septum
b) Perimembranous (conoventricular, paramembranous, Type II)
i) 80% of all VSDs
ii) May be seen w/malalignment of conal septum
a) Anterior in TOF (RVOTO)
b) Posterior in interrupted arch (LVOTO)
iii) Relations
a) Between conal (outlet) and trabecular (muscular) septum
b) Posteroinferior edge can extend to TV in area of anteroseptal commisure
c) May extend to noncoronary cusp of AV, causing aortic regurgitation
iv) Anterior leaflet of TV may bulge into defect during systole appearing as aneurysm of membranous septum (angiography)
v) LV to RA shunt if anteroseptal commisure becomes adherent to defect
c) Subarterial (outlet, conal, supracristal, subpulmonary, infundibular, Type I)
i) 5-10% of all VSDs
ii) Superior edge in conjoined annuli of aortic and pulmonary valves
iii) Right or non-coronary cusp of AV is relatively unsupported, may prolapse, cause AR
d) Atrioventricular canal type (inlet, Type II w/ extension into inlet septum)
i) <5% of surgically treated VSD
ii) Relations
a) Posterior rim runs along septal leaflet of TV to central fibrous body to anterior leaflet MV
b) Superiorly, usually extends to membranous septum
c) No intervening muscle between defect and TV
d) Medial papillary muscle (Lancisi) attached to anterior margin of defect
iii) Anterior leaflet of MV may be cleft
e) Muscular (Type IV)
i) Muscular tissue all the way around the defect
ii) Frequently multiple
iii) Location - surgical approach
a) Anterior - approached through RV-high transverse ventriculotomy
b) Inlet septum - separated from TV by muscle - approached through TV
c) Mid-muscular - approached through TV
d) Apical-LV apex (Glenn’s)-RA or low, vertical R ventriculotomy (Kirklin)
e) Outlet, muscular VSD’s similar to subarterial (physiologically) but have a rim of muscle between defect and semilunar valve annuli
iv) Swiss cheese septum
a) True form (multiple openings on RV and LV sides of defect) is rare - may not be totally correctable
b) Septal band on RV side can give appearance of multiple openings

3. Atrioventricular conduction system
a) Anatomy
i) Triangle of Koch
a) Tendon of Todaro superiorly
b) Tricuspid annulus inferiorly
c) Coronary sinus orifice posteriorly
d) Apex is central fibrous body and atrial portion of membranous septum
e) Exact position of AV node in triangle may be variable
ii) His bundle (direct continuation of A-V node
a) Passes through rightward part of right trigone of central fibrous body
(1) This is just inferior to the commisure between the septal and anterior leaflets of TV
b) Continues along posteroinferior margin of membranous septum and crest of muscular septum - gives off branches that form LBB
(1) This is just beneath the commisure between right and non-coronary cusps of aortic valve
c) Lies on left side of septum in 75-80%
b) Techniques to avoid injury
i) Suture along right ventricular side of septum to avoid His bundle on left side of muscular septum
ii) When membranous septum is deficient
a) A-V node migrates posteriorly toward crux of heart (junction of AV and interventricular grooves)
b) His bundle passes along posteroinferior rim of defect
c) Avoid this by placing sutures a few millimeters from posteroinferior rim, and not penetrating the septum
d) Anterior to muscle of Lancisi - less danger of conduction injury
iii) A-V canal type VSD - conduction tissue runs along posteroinferior border of defect
iv) Inlet muscular VSD - conduction tissue is anterosuperior to defect

4. Pathophysiology
a) Qp/Qs = ratio of pulmonary to systemic flow
i) (aortic O2 sat - central venous O2 sat)/(pulm venous O2 sat - pulm art sat)
ii) Can assume PV sat = aortic sat
b) Increased pulmonary flow
i) LA enlargement, LV overload
ii) Pulm HTN is reversible in early stages
iii) Intimal proliferation and medial hypertrophy will eventually lead to fixed, irreversible pulm HTN
iv) Histologic severity of pulmonary hypertensive dz correlates directly with PVR and inversely with magnitude of shunting
v) Gradual increase in PVR decreases L?R shunting and decreases CHF as pulm vasc bed replaces LA pressure as determinant of flow resistance across lungs
vi) Eisenmenger’s syndrome
a) Cyanosis and R heart failure due to reversal of shunt flow
b) PVR is greater than SVR
c) VSD closure in this setting associated with severe, acute R heart failure
c) Nonrestrictive: little resistance to flow, approximating at least the diameter of the aortic valve
i) RV systolic pressure equal to LV pressure
ii) Large increase in pulmonary blood flow
a) Inversely proportional to pulmonary vascular resistance
iii) Multiple small VSD’s may hemodynamically act like a large VSD d) Small VSD
i) VSD presents resistance to flow, preventing increase in RV pressure
ii) Qp/Qs rarely exceeds 1.5
e) Moderate VSD
i) Qp/Qs = 1.5 - 2.5
ii) Less likely to cause fixed pulmonary hypertensive vascular disease

5. Natural history
a) Tendency for spontaneous closure vs. risk of hypertensive pulmonary vascular disease
b) Severity of symptoms depends on shunt volume across VSD
i) Qp/Qs increases as PVR decreases in first weeks of life
ii) Symptoms = recurrent resp infections, SOB, failure to thrive
iii) PA’s can exert extrinsic compression on airways and increased air trapping
iv) Untreated symptomatic children have 10% 1-year mortality
c) Irreversible pulmonary HTN unusual in 1st year of life
d) Untreated children w/large VSDs will develop Eisengmenger’s complex
i) Hemoptysis, polycythemia, cerebral abscess/infarction, R heart failure
ii) Preceded by resolution of CHF
iii) Cyanosis by end of 1st decade of life
iv) Premature death by age 35
e) Spontaneous closure
i) Perimembranous A-V canal and subarterial
ii) Inversely related to pt age
a) 1 mo.: 80% will close (large VSD)
b) 6 mo.: 50%
c) 12 mo.: 25%
f) Infundibular PS or RVOTO in 5-10% w/nonrestrictive
i) Myocardial hypertrophy
ii) R to L shunt when RVOTO severe
iii) May protect pulmonary vascular bed
g) Bacterial endocarditis - 0.15-0.3% per year - more common in small & moderate VSDs
h) Aortic valve insufficiency
i) Subarterial perimembranous (percentage)
ii) Right and/or non-coronary cusp
iii) May be an indication for surgery (VSD closure)

6. Diagnosis
a) Clinical features
i) Harsh pansystolic murmur
a) Small are usually asymptomatic
ii) Large (low PVR)
a) CHF
b) Tachypnea, hepatomegaly, failure to thrive, repeated pulmonary infections
c) Precordial pansystolic murmur
d) Prominent S3, diastolic murmur at apex (increased flow across MV)
iii) Large (elevated PVR)
a) Shunt is bi-directional
b) Softer or absent systolic murmur
c) Absent diastolic murmur
d) Loud P2
e) Precordial thrill
b) ECG
i) Small defect - normal ECG
ii) Large defect
a) LAE, LVH early
b) LVH, RVH as PVR rises
c) CXR
i) Small defect - normal CXR
ii) Significant L to R shunting
a) Cardiomegaly due to LA dilatation
b) Increased pulmonary flow
d) Echocardiography
i) Size, location of defect; estimate RV pressure, magnitude of shunting
ii) In neonates with symptomatic, isolated VSD, echo alone may suffice
e) Cardiac catheterization
i) Mandatory in older children to assess PVR and pulmonary HTN
ii) Shunt volume, Qp/Qs , irreversible component of pulmonary HTN

7. Treatment
a) Dictated by symptoms, associated defects, age at presentation, PVR, location
b) Surgical indications
i) Early in life - intractable CHF
ii) Failure to thrive - most common
iii) Asymptomatic - delay to 12 mo of age (spontaneous closure)[Mavroudis = 6mo]
iv) 6 mo. + pulm HTN = operate
v) Small defect, asymptomatic - watch (controversial after age 10)
vi) A-V canal and subarterial - no tendency to close, operate early
vii) PA banding
a) Swiss cheese type + symptomatic
b) VSD w/ straddling A-V valve
c) Contraindication to surgery
i) Fixed pulmonary HTN (greater than 8 Wood units) [Wood units = mm Hg/L/min/m2]

8. Operative technique
a) Ligate ductus soon after institution of CPB
b) Most repaired through RA (except subarterial and outlet muscular)
i) Subarterial - via pulm valve
ii) Muscular - depends upon location
a) Mid-muscular - RA
b) Right or left ventriculotomy may be needed for anterior muscular
c) AI - patch VSD closure may be enough (mod-severe may require repair)
d) Prosthetic patch (PTFE, dacron)
e) Avoid conduction tissue (posteroinferior rim of VSD)
f) Hypothermic (18°C) circulatory arrest helps in small (<8kg) infants

9. Results
a) Early mortality approaches 0
b) Multiple VSD’s, associated anomalies = 7% mortality c) Arrhythmia
i) RBBB = 80% (R ventriculotomy)
ii) RBBB = 34% (R atriotomy)
iii) RBBB + L anterior hemi-block = 8-17%
iv) CHB approaches 0
d) Residual VSD = 0.7-2%