Cardiovascular anatomy Flashcards
(39 cards)
Double aortic arch
Persistence of both 4th arches; fuse distally to form descending aorta
Causes constriction of the esophagus AND trachea; only vascular ring anomaly where tracheal compression causes clinical signs
Persistent right aortic arch
Persistence of the right 4th arch
Contriction of esophagus and trachea due to left ligamentum arteriosum or patent ductus arteriosus
Aberrant left subclavian
Failure of left 7th intersegmental artery to migrate cranially to reach the 4th arch before separating from dorsal aorta
PRAA is always present
2 forms:
- Right ligamentum arteriosum + PRAA + aberrant LSA = ONE SITE of constriction
- Left LA + PRAA + aberrant LSA = TWO SITES
Aortic coarctation
Severe narrowing of aortic lumen at aortic isthmus (between the LSA and ductus arteriosus) due to spread of ductal tissue into aorta causing constriction at birth
Leads to LV hypertrophy and L CHF
Radiography:
1. indentation of the aorta with severe dilation distally 2. Rib notching - blood shunting into the intercostal and costocervical arteries
Use common carotid artery for angiography approach.
Patent ductus arteriosus
PDA caused by partial or complete lack of ductal smooth muscle in the ductus arteriosum
- types I and II are funnel-shaped, tapering near the PA
- type III is tubular with no tapering and is not amenable to coiling; these often lead to R→L shunting due to severe postnatal pulmonary hypertension
Shunts located along the left ventral aspect of the descending aorta immediately distal to the left subclavian artery and extend cranioventrally and to the left to connect with the dorsal wall of the MPA adjacent to the PA bifurcation.
Eisenmenger’s syndrome
Eisenmenger syndrome (ES) is a constellation of symptoms that arise from a congenital heart defect; initially result in a left-right shunt, which develops into severe pulmonary arterial hypertension (PAH) and elevated vascular resistance –> the left-to-right shunt will become a right-to-left shunt, resulting in significant hypoxemia and cyanosis.
Common with ASD, VSD, and PDA
Ductus arteriosus
Ductus arteriosus is derived from the left 6th aortic arch; closes 7-10 days after birth due to rapid increase in PaO2 inhibiting prostaglandins → ductal smooth muscle constriction
Diagnosis of PDA
L→R PDA Diagnostics
- Radiographs
Generalized cardiomegaly with hypervascular pattern
Bulges at descending aorta near PDA, left auricle, MPA
- Angiography
Aortic injection
Opacification of PA following injection with aortic dilation and visualization of ductus
R→L PDA - Radiographs Right-sided cardiomegaly Dilated MPA Variable appearance of lobar and peripheral arteries
- Angiography
Injection must be made in RV or MPA
Atrial Septal Defect
ASD types
- Ostium secundum defect - at or near foramen ovale in upper atrial septum
- Ostium primum defect - lower atrial septum
- Endocardial cushion defect (cats) - adjacent to AV valve at septum primum
Normal development of atrial septa and ventricular septa
Atria and ventricles are a common chamber initially then become a 4 chamber compartment by growth of the cardiac septa
- Atrioventricular partitioning: endocardial cushions
- Atrial partitioning
- 1st septum: septum primum –> grows from the dorsal wall of the atrium ventrally towards the endocardial cushions –> a large opening forms which allows blood to shunt from R→L atrium: ostium (foramen) primum –> Ostium primum disappears and a new foramen develops → ostium secundum
- 2nd septum: septum secundum –> muscular partition arising from the atrial wall, to the right of the septum primum, both dorsal and ventral; not continuous septum –> Foramen ovale → space in between septum
Ventricular partitioning - mainly occurs by inward growth of the ventricular walls.
Patent foramen ovale
Not considered a true ASD because the atrial septum forms normally
L→R shunt
- Shunting occurs during diastole due to low pressure difference across defect.
- Radiographs: right-sided cardiomegaly (RAE, RVE), pulmonary hypervascular pattern, +/- MPA dilation
R→L shunt: occurs with concurrent severe PS, TVD, or PH
What is the most common cardiac anomaly in cats?
VSD
Ventricular septal defect
Defect in the perimembranous septum located high on the ventricular septum.
L→R shunt (uncomplicated VSD)
- Shunting occurs during systole is degree is dependent on defect diameter
- Consequence –> RAE, RVH (concentric), PAE, LAE, LVH (eccentric)
- Large shunts: volume overload of left +/- right heart leading to LCHF +/- RCHF
- Aortic regurgitation can occur due to secondary Ao valve malformation from the shunt being in close proximity to the LVOT.
R→L shunt (complicated VSD)
- Eisenmenger’s complex (severe PH) or TOF
- Diffuse cyanosis + secondary polycythemia and hyperviscosity syndrome
Aortic stenosis
Subvalvular types (most common
1. **Fibrous ring below the valve (static)
2. Dynamic SAS occurs in cats with HCM due to
systolic anterior motion
May be associated with mitral or aortic valve dysplasia
Consequences:
- LVH (concentric), LAE, poststenotic dilation of the aorta
- Aortic insufficiency (mild)
- Mitral insufficiency
- Bacterial endocarditis - mild to moderate gradient
- Fatal arrhythmias - severe gradient
- Rarely LCHF
Diagnosis of aortic stenosis
Radiographs: LAE, LVE, post-stenotic dilatation of the aorta, +/- pulmonary venous congestion
Angiography:
- LV injection reveals subvalvular stenosis and A/S ratio > 1 (aortic to sinus of Valsalva).
- Supravalvular injection is also made to rule out aortic insufficiency.
Pressure gradients (▵P = 4V22)
Normal: 4-16 mmHg (1-2 m/s aortic velocity)
Mild: < 40 mmHg
Moderate: 40-80 mmHg
Severe: > 80 mmHg (poor prognosis)
Velocity measurements
> 2.5 m/s = SAS
< 2 m/s = normal
2-2.5 m/s = gray zone
Pulmonic stenosis
Valvular (most common), subvalvular, supravalvular
Subvalvular type in English bulldogs and Boxers associated with anomalous left coronary artery where left main coronary artery arises from single right coronary artery and encircles the RVOT.
TVD can occur concurrently with PS (RAE)
Consequences RVH (concentric) RCHF rare unless concurrent TVD MPA post-stenotic dilatation Pseudohypertrophy of LV due to ↓ PL
Treatment
- Balloon valvuloplasty in moderate (probable) to severe cases (always) if the valves are thin and the annulus is not hyperplastic
- Contraindication: anomalous left coronary artery (this is controversial now)
Diagnosis of pulmonic stenosis
Radiographs
- RVE
- MPA dilation
- Pulmonary hypoperfusion or normal perfusion
Angiography:
RV injection
Pressure gradients
Mild: < 50 mmHg
Moderate: 50-80 mmHg
Severe: > 80 mmHg
Mitral valve dysplasia
Common cardiac anomaly in cats, bull terriers, large breeds
Consequences:
massive LAE, LVH (eccentric), LCHF → PH → RCHF
What makes up the AV apparatus?
major and minor leaflets, chordae tendinae, ventricular wall, valvular annulus and atrium
What abnormalities are seen of the AV apparatus?
Thickening of the valve leaflets
Underdeveloped chordae tendinae and papillary muscles
Incomplete separation of the valve components Agenesis of valvular tissue
Tricuspid valve dysplasia
Tricuspid valve dysplasia - Labs, GSD, Old ESD, cats
Concurrent patent foramen ovale or ASD possible
Consequences:
massive RAE, RVH (eccentric), RCHF
Normal endocardial cushion development
Dorsal endocardial cushion fuses with the septum primum to close the ostium primum in the atrial septum.
The dorsal and ventral endocardial cushions fuse to divide the common AV canal into the left and right AV canals.
AV septum → normal partition between the LVOT and RA
Two separate AV valve rings
Endocardial cushion defect
Dorsal and ventral endocardial cushions do not close –> cushions cannot fuse with the septum primum to close the ostium primum –> AV valves are placed abnormally low in the ventricle and the aortic valve placed abnormally high → longer LVOT
AV canal defects - AV septum is absent and a common AV orifice with a common fibrous ring and 5-leaflet valve are present.
Complete AV canal defect:
All four chambers communicate with each other through a septum primum ASD, high VSD, and AV valve regurgitation.
Partial AV canal defect (low ASD or high VSD)
How do you distinguish ASD/VSD cases from AV canal defect cases?
AV canal defects have concurrent moderate to severe mitral regurgitation
