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
What are malalignement or conotruncal VSDs
defect present from ventriculo-arterial a malalignment
o Loss/malposition of supraventricular crest and portion of membranous/muscular outlet septum
o Look for fibrous continuity btw valves to further classify
Significance of IVS aneurysm
o May represent spontaneously closed defects
Un/non-committed VSD
- VSD NOT anatomically related to/close to great vessel
o Separated by considerable muscle - Not an anatomic definition
o Used to define VSDs in DORV when distant from both arterial valves
Committed VSD
- VSD was anatomically related to/close to great vessel
Doubly committed VSD
= infundibular VSD
can be muscular or rimmed by semilunar valve tissue
o Considered doubly committed subarterial when
Little to no muscule btw OT components
* Always associated w loss of muscular outlet septum
Absence of Subpulmonary infundibulum
Ao and PV leaflets are in fibrous continuity
What is the infundibular septum
separates LVOT and RVOT
o Subpulmonary infundibulum:
Sleeve support leaflets of PV
Separates RVOT from surface of heart
Other names for infundibular VSD
o Supracristal
o Subpulmonary
o Subarterial
o Doubly committed
o Outlet
Subaortic VSD
Most frequent type of DORV
Ao is to R of PA
VSD is more closely related to Ao vs PA
Presence of bilateral conus separates semilunar valves
* Ao conus: btw AoV and MV anterior leaflet
Subpulmonary VSD
Dilated PA
VSD is supracristal, subjacent to PV
Pulmonary conus
* Separate MV anterior leaflet and PV
* No conus btw VSD and PV
Conus septum: separates AoV and PV
2D echo findings
- R parasternal LAX LV outflow view
o Junction of muscular septum → anterior Ao wall
o Cannot see supracristal defect - R parasternal SAX view at level of Ao and LA/PA
o High perimembranous defects
Under TV and above Ao
o Supracristal defects: proximal to PV - Muscular VSD: anywhere along muscular septum
- Avoid 4 chamber views (echo drop out)
- Aneurysmal dilation of membranous portion of IVS in RV
o If perforated, usually ventral portion of aneurysmal pocket
o Can be associated with spontaneous closure of VSD
M-Mode echo findings
- TV flutter in systole (38% of dogs w VSD)
Spectral color Doppler findings
- AI: often seen, especially with supracristal VSD
o AoV prolapse - Restrictive VSD: PG should >80mmHg (or 5m/s)
- Lower PG indicative of larger defects, ↑ RVP
- Flow profile across VSD: plateau shape
o Represent PG from R to L ventricle - Qp:Qs>2 → significant shunting
Describe inlet VSD
- IVS btw MV and TV: extend from valve to trabeculae
- Muscular or perimembranous
o Aligned IAS and IVS
o Malalignment of septums w/ straddling TV
Inlet VSD other names
AVSD canal type VSD
perimembranous VSD w/ inlet extension
Describe muscular VSD
- Apical portion of IVS : midseptal, apical, anterior, inferior
- Muscular borders
- Spontaneous closure if small (Hu)
- Multiple defects: swiss cheese IVS
Describe outlet VSD
- Smooth wall outlet portion btw RVOT and LVOT
- Absence/hypoplasia of conal septum = under PV
o Fibrous continuity Ao → PV
Outlet VSD other names
o If absent conal septum: conal septal, infundibular, doubly committed juxtaarterial, supracristal, subpulmonic/subarterial
o If conal septal malalignment: conoventricular, perimembranous w/ outlet extension
Describe perimembranous VSD
- Base of heart: separate TV from AoV
o Behind septal TV leaflet
o Below R coronary Ao cusp - Fibrous continuity TV → AoV
- Most common
o Spontaneous closure can occur → aneurysm - Restrictive flow → behind TV tissue
- AI: AoV cusps prolapse from venturi effect
Perimembranous VSD other names
infracristal, subaortic
What is Gerbode defect
- Membranous IVS at Mv and TV offset
o AV node penetrating bundle - Shunt LV → RA
Pathophys VSD
- L → R shunting: L sided enlargement
o LV volume overload from shunt + AI
o Leads to CHF - Pulmonary overcirculation → ↑ PVR → Eisenmenger
Hemodynamic significance depend on:
o Size of defect: small restrictive vs large (LVP = RVP)
o PVR and SVR
PE VSD
o Systolic murmur: inversely proportional to defect size
o Diastolic murmur: AI
To and fro possible
ECG VSD
- LAE: wide P waves
- LVE: ↑ R wave amplitude
CTX VSD
- Left sided cardiomegaly
- Pulmonary overcirculation
Natural history depending on size
- Small VSD: usually well tolerated
o No treatment needed
o Can close spontaneously: reported in dogs - Moderate VSD: variable px
- Large VSD: will likely develop CHF
How to reduce shunt flow
o Arteriolar vasodilation → ↓ SVR
o PA banding → ↑ PVR and RVP
Cardiac KT oximetry
O2 step up in RV and PA
Cardiac KT pressure study
o Large defect: RVP = LVP
o Pulmonary vascular disease 2nd to pulmonary overcirculation → ↑ PVR and PCWP
Angio cardiac KT
LV to RV shunting
o AI can be identified w/ aortic angio
