2 – Congenital Heart Defects

Question 1

3 shunts in fetal circulation

Answer 1

• Ductus venosus
• Foramen ovale
• Ductus arteriosus
• *closed after birth

Question 2

Severe cardiac malformations

Answer 2

• Incompatible with INTRAuterine life=embryonic death or fetal abortion

Question 3

Cardiac malformations compatible with INTRAuterine life

Answer 3

• Result in postnatal heart failure or sudden death

Question 4

Minor cardiac malformations well compensated by physiologic adaptive mechanisms

Answer 4

• Cause no clinical signs
• Defects are incidental finding at slaughter or post-mortem examination

Question 5

Etiological diagnosis of congenital heart defects can be due to

Answer 5

• Genetic
• Maternal infections (parvovirus, BVD)
• Nutritional deficiencies (vitamin A, zinc)
• Drugs (ex. thalidomide)
• Other teratogens (radiation, fetal hypoxia, maternal diabetes)
• Multifactorial

Question 6

Most common congenital heart defects: ‘groups’

Answer 6

• Defects that cause volume overload
  o L to R shunts
  o Valvular regurgitation
• Defects that cause pressure overload
• Defects that cause early cyanosis (R to L shunts)
• Miscellaneous

Question 7

L to R shunts examples

Answer 7

• Patent ductus arteriosus
• Atrial septal defect
• Ventricular septal defect

Question 8

Valvular regurgitation

Answer 8

• Valvular dysplasia

Question 9

Defects that cause pressure overload

Answer 9

• Aortic and pulmonic stenosis

Question 10

Defects that cause early cyanosis (R to L shunts)

Answer 10

• Tetralogy of Fallot
• Transposition of great arteries

Question 11

Miscellaneous congenital heart defects

Answer 11

• Persistant right aortic arch
• Ectopia cordis

Question 12

Patent ductus arteriosus (PDA)

Answer 12

• Communication between pulmonary artery and aorta=close after birth=ligament arteriosum
• Particularly in DOG (make it after 3 weeks)

Question 13

Hemodynamics of patent ductus arteriosus

Answer 13

• L to R shunt between aorta and pulmonary artery
• Increased pulmonary blood flow (hyperflux)
• Pulmonary hypertension
• Pressure overload in RV and volume overload in LV

Question 14

Left to right shunts

Answer 14

• Increased vascular resistance -> medial hypertrophy or irreversible obstructive intimal lesions
• Shunt reverses (R to L)
• Late cyanosis (Eisenmenger syndrome)

Question 15

2 ways communication between L and R atrium may occur POSTnatally

Answer 15

1. Persistence of the fetal foramen ovale
2. True atrial defect in which there is a failed closure of atrial septum

Question 16

Atrial septal defect (ASD)

Answer 16

• Minor ones have little clinical significance
• 20% of humans, probe can be passed through, but it is not functional=no shunt

Question 17

Hemodynamics of atrial septal defect

Answer 17

• Large defect: excessive blood flow from L to R atrium -> volume overload of R ventricle -> R ventricle hypertrophy
• Pulmonary congestion (O2 blood returns to the lungs)

Question 18

Ventricular septal defect

Answer 18

• One of the most common defects in domestic animals
• High (close to AV valve) or low (close to apex=rare)

Question 19

Hemodynamics of ventricular septal defect

Answer 19

• L to R shunt
• R ventricle pressure and volume overload
• R ventricle hypertrophy
• R heart failure (if uncompensated)
• L ventricle hypertrophy
• *blood shunt reverse to R to L and cause cyanosis (Eisenmenger complex)

Question 20

Valvular dysplasia

Answer 20

• Often difficult to assess post-mortem (requires experienced practioner)
• Tricuspid dysplasia
• Mitral dysplasia

Question 21

Tricuspid dysplastic valves show one or more of the following features

Answer 21

• Diffuse or focal thickening of leaflets
• Missing or short chordae tendineae
• Thick or short papillary muscles
• Direct fusion of leaflets to papillary muscles or the ventricular wall

Question 22

Tricuspid dysplasia

Answer 22

• Most common in cats (dogs, retrievers)
• ECCENTRIC hypertrophy of R ventricle
• Massive DISTENSION of R atrium

Question 23

Mitral dysplasia

Answer 23

• Most common in cats
• ECCENTRIC hypertrophy of L ventricle
• DISTENSION of L atrium

Question 24

Mitral dysplastic valves show one or more of the following features

Answer 24

• Short thick leaflets
• Short thickened chordae tendineae
• Upward malposition of atrophic or hypertrophic papillary muscles

Question 25

Pulmonic stenosis

Answer 25

• Narrowing of pulmonic vavle
• Valvular, subvalvular, supravulvular
• Usually due to constricting band of fibrous or muscular tissue
• Post-stenoic arterial dilation often found in artery, distal to stenosis

Question 26

Pulmonic stenosis hemodynamics

Answer 26

• Pressure overload of RV
• RV hypertrophy
• If uncompensated=R heart failure

Question 27

Pulmonic stenosis necropsy findings

Answer 27

• Heart has broad base
• Hypertrophic RV
• Narrow lumen of pulmonary artery (may show post-stenotic dilation)

Question 28

Aortic and subaortic stenosis

Answer 28

• Dogs and pigs
• Constricting band of fibrous or muscular tissue encircling LV outflow tract

Question 29

Hemodynamics in subaortic stenosis

Answer 29

• Pressure overload of LV
• LV hypertrophy (concentric)
• Post-stenotic dilation of aorta
• If uncompensated: L heart failure w/pulmonary edema

Question 30

Tetralogy of Fallot

Answer 30

• 4 anomalies (3 congenital, 1 consequence)
  1. VSD
  2. Overriding aorta
  3. Pulmonic stenosis
  4. R ventricular hypertrophy

Question 31

Transposition of the great arteries

Answer 31

• VENTRICULOARTERIAL DISCORDANCE
• Aorta arises from R ventricle
• Pulmonary artery arises from L ventricle
• Not able to survive unless a shunt exists for adequate mixing of blood (R to L shunt and early cyanosis)

Question 32

Persistent right aortic arch

Answer 32

• Dogs
• Aorta incorrectly formed from right 4th arch rather then the left
• Trachea and esophagus enclosed by aortic arch, pulmonary artery and ligamentum arteriosum
• No hemodynamic abnormalities or signs of heart failure

Question 33

Esophageal constriction in persistent right aortic arch

Answer 33

• Dysphagia
• Regurgitation
• Megaesophagus

Question 34

Ectopia cordis

Answer 34

• Mostly found in stillbirths or aborted fetuses
• Animals may survive for days, weeks or more