VSD Flashcards
Components/regions of IVS
o Inlet portion
TV orifice → papillary muscles
Smooth walled
Separates MV and TV valves
o Apical/trabecular portion
Heavily trabeculated
Primarily apical, from attachment of TV leaflets → apex and upward to crista supraventricularis
o Outlet/infundibular/conal portion
Btw RVOT and LVOT
Smooth walled, cranial to crista supraventricularis
o Membranous portion
Below Aov on L side
Cranial aspect of septal TV leaflet, btw TV and PV on R side
Separate AoV from TV
What is the crista supraventricularis
o Muscular ridge in RV, U shaped
o Part of infundibular/outlet septum → smooth walled
o Btw TV and PV
o At jct of RVFW and IVS
Embryologic development of IVS
o IVS develops from apical → basilar
Inlet and membranous portions are last to form
What is a VSD
communication btw ventricles
Prevalence
7% dogs, 15% cats with congenital defects
Breeds predispositions
WHWT, Lakeland terriers, English Bulldogs, English Springer Spaniel
Most common congenital defect in lamas, cows, horses
What determines the clinical significance of the defect
associated w size/ location, concomitant defects
What is the most common type
- Most commonly perimembranous defect (80% of cases)
o Below base of R or noncoronary cusp when viewed from LV
o Adjacent to cranial edge of septal TV leaflet, caudoventral to supraventricular crest
Pathophysiology of L to R VSD, small vs large defect
o L to R VSD: RV is a conduit → pulmonary overcirculation → LV volume overload
Normal RV size
* Simultaneous ventricular systole as blood is shunted to R side → enter RVOT and bypass RV
Small defect: insignificant volume overload
Large defect: significant L sided volume overload
* Can also cause R sided overload
* Chamber dilation is α to qty of shunting
What determines the amount of shunting in non restrictive defects
PVR
RV = LV systolic pressure
PAP = SAP
What can happen to PA
o MPA enlargement (all length) → ↑ blood flow
Distinguish from post stenotic dilation where enlargement is distal to valve
Hemodynamics of restrictive defects
o Restrictive defect: LV > RV systolic pressure
Resistance to flow across defect
Little to no functional importance → restrict magnitude of shunting
DO NOT ELEVATE PAP
Classification of VSDs
Variable
Muscular
Juxtaarterial
Perimembranous
Muscular VSD: location, features
Entirely surrounded by muscular septum
Apical or mid ventricular
* Central: mid muscular
o Multiple channels on RV side
o Coalesce into single defect on LV side
o Posterior to trabecula septomarginalis
* Apical: most frequent
o Often large
o Multiple channels on RV side
o Coalesce into single defect on LV side
* Marginal: small defect along RV septal jct
Multiple muscular defects → swiss cheese septum
Rare in dogs/cats
Juxta-arterial VSD: location, features
in outlet septum, below PV and AoV
High incidence of AI as AoV leaflet prolapse into defect
Fibrous continuity of AoV and PV
Perimembranous VSD: location, features
surrounded by membranous septum
Cranial aspect of septal TV leaflet
Paramembranous: large, encroaching supraventricular crest and extending toward RVOT
Fibrous continuity of AoV and TV
Defects can further described based on
location: apical, outlet, inlet
Inlet VSD
can be part of perimembranous or muscular septum
Historically directly ventral to septal TV leaflet
Associated w endocardial cushion defect
Often with ASD → AVSD
Outlet VSD
perimembranous or muscular
Below AoV on L side
Below PV on R side
Other classifications
- Older classification according to position of VSD in relation to supraventricular crest
o Infracristal → perimembranous
o Supracristal → juxtaarerial