Ventricular septal defect

Embryogenesis

&

Classification

Introduction

First described by Roger in 1879 Most common congenital heart disease 1.5 – 2.5/1000 live births 20% of CHD Most common disorder in various chromosomal

disorders Has Multifactorial etiology

Ventricular septum Complex non – planar structure; 4 components Inlet septum – lightly trabeculated; extends from

tricuspid annulus to attachments of tricuspid valve

Trabecular septum – heavily trabeculated; trabecular septum extends from inlet out to apex and up to smooth-walled outlet

Outlet septum – non trabeculated; extends up to pulmonary valve

3 diverge from small membranous septum

Ventricular septation Ventricles derived from 2 imporatant

components of primitive heart – inlet & outlet Three septal components are necessary for

septation Expansion of inlet & outlet components leads to

formation of partial septum between two – primary interventricular septum

Two intrinsic septum in two segments called inlet & outlet septum

mainly formed by inlet and primary septa

Ventricular septation growth of two ventricles on either side causes

primary septum to be more prominent inlet septum result from muscular

trabeculations in inlet region of ventricles in same plane as that of atrial septum third component comes from endocardial

cushion tissue – membranous portion of ventricular septum

septation starts at about 37 days of gestation & complete by 49th day of gestation

Muscular septum During 5th week(day 30), muscular fold extends from

anterior wall of ventricles to floor appear at middle of ventricle near apex and grows

towards AV valves with concave ridge Most of initial growth achieved by growth of two

ventricles on each side of ventricular septum In addition trabeculations from inlet region coalesce grows into ventricular cavity at slightly different plane

than primary septum inlet interventricular septum is at same plane as that of

atrial septum

Ventricular Outflow septation from horse-shoe shaped condensed mesenchyme

embedded in endocardial cushion tissue Just proximal to level of development of aorto-

pulmonary valves Condensed mesenchyme will come in close

contact with outflow tract myocardium Area just above bulboventricular fold appears to

reach out to condensed mesenchyme Participate in septation of outflow tract by

providing an analogue to muscle tissue

Primary foramen Communication between inlet & outlet

components Exists because primary septum is incomplete Divided into R & L by growing septation L component forms LVO Due to differential growth, LV apex formed by

inlet component RV apex formed by outflow component

Interventricular Foramen Bordered by concave upper ridge of muscular

interventricular septum and fused AV canal endocardial tissue, closes at end of week 7

Achieved by growth of three structures: right and left bulbar ridges and posterior endocardial cushion tissue

Closes interventricular foramen and connect ventricular septum to outflow septum

Connecting right ventricle to pulmonary trunk and left ventricle to aortic trunk

Outflow Tract Includes ventricular outflow tract and

aortopulmonary septum Three embryological areas, conus, truncus and

pulmonary arterial segments Each segment develop two opposing ridges of

endocardial tissue Opposing pair of ridges and those from various

segments meet to form septum separating two outflow tracts and aortopulmonary trunks

VSD CLASSIFICATION

PerimembranousOutletInletmuscular

Anatomic classificationPhysiological classification

Perimembranous

most common defect 80% of surgical and autopsy series usually extends into muscular, inlet, or outlet areas synonyms: infracristal, membranous

Outlet

5%-7% of autopsy and surgical series (29% in Far East)

situated just beneath the pulmonary valve synonyms: supracristal, conal, infundibular,

subpulmonary,doubly committed subarterial

Inlet

5%-8% posterior and inferior to perimembranous defect

Muscular

5%-20% Central: mid-muscular, may have multiple

apparent channels on RV side and coalesce to single defect on LV side

Apical: multiple apparent channels on RV side may be single defect on LV side as with central defect

Marginal: along RV septal junction "Swiss cheese" septum: large number of

muscular defects

a, outlet defect; b, papillary muscle of the conus; c, perimembranous defectd, marginal muscular defects; e, central muscular defects; f, inlet defect; g, apicalmuscular defects

Physiological classification

Determines effect of VSD on patient

Depends on size of defect

Resistance of flow through lungs (PVR)

Small defect with low PVRModerate defect with variable

PVRLarge defect with mild to

moderate PVRLarge defect with high PVR

Size Also classified as…

Restrictive

Nonrestrictive

Association

Part of many complex structural heart diseases Secondary AR RVOTO Subaortic obstruction

VSP-LAX

P-SAX

AP-5CAP-4C P-SAX b

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