Cardiology: Congenital Heart Disease

Question 1

Use the following table to match up the following causes of murmurs
* Pulmonic stenosis
* Aortic Stenosis
* VSD
* Mitral dysplasia
* Tricuspid dysplasia
* PDA

Answer 1

1. PDA- continuous left heart base, dorsal/forward
2. Aortic stenosis- left base 4th IC, weak pulse
3. Pulmonic stenosis- left base 3rd, radiates up IC space
4. VSD- cranioventrally on right
5. Mitral dysplasia- left MV 5th IC
6. Tricupsid- right, 4th IC

Question 2

What is an innocent murmur?

Answer 2

Puppies and kittens may have soft systolic heart murmur- left heart base
Should disappear by 20 weeks old

Due to change from foetal haemoglobin to adult

Question 3

1. What is a patent ductus arteriosus?
2. What does it cause?
3. What breeds are predisposed?
4. What is the characteristic murmur sound?

Answer 3

1. The ductus arteriosus fails to close at birth
2. Causes a shunt between aorta (high pressure) to pulmonary trunk (low pressure)- left to right
3. GSDs, Collies, CKCS, Bichon- females more common
4. Waxing through systole and waning through diastole- high and cranial in the axilla (pit) left

Question 4

Describe what happens with a PDA and therefore the effects?

Answer 4

• Shunt from descending aorta to pulmonary artery- aortic pressure exceeds PA pressure- continuous
• Lung field over-circulated
• Increased volume of blood to left side of heart (L volume overload)
• LA and LV enlargment (eccentric hypertrophy)
• Femoral pulse may be ‘bounding’

Question 5

What happens if a PDA is untreated?

Answer 5

Results in left sided congestive heart failure and LV myocardial failure before the dog is 7

Question 6

What is eisenmenger’s physiology?

Answer 6

• Rarely a PDA with pulmonary hypertension can cause the shunt to reverse
• murmur stops being continuous
• Animal may show cyanosis- possibly on exertion
• Common in cats

Question 7

What are the different diagnostic tests that can be used for heart disease?

Answer 7

• Thoracic radiographs
• ECG
• Doppler Echo

Question 8

What do the following diagnostic tests show for PDA?
1. Thoracic radiographs
2. ECG
3. Doppler Echo

Answer 8

1. LAE, LVE, pulmonary overcirculation- ‘triple knuckle’ on DV- aortic arch, PA and left auricular appendage
2. Often very tall R waves, Evidence of LAE, LVE
3. Difficult- Diastolic turbulence in the PA

Question 9

How is PDA treated?

Answer 9

Curable if early
* Surgical ligation of PDA
* Device based- keyhole, ACDO- encourage clot formation
* Do not close Eisenmengers physiology

Question 10

1. What is the most common congenital heart defects in dogs?
2. What breeds are predisposed?

Answer 10

1. Aortic stenosis
2. Boxer and newfoundland

Question 11

1. What can cause aortic stenosis?
2. What does it result in?

Answer 11

1. Can be valvular or sub-valvular- lesions rane from ‘nodules’ to a complete or partial circumferential fibrotic band or muscular ridge
2. Pressure overload on the LV resulting in LV concentric hypertrophy

Question 12

What are the clinical signs of Aortic stenosis?

Answer 12

• Syncopal episodes and excercise tollerance- consequence of obstruction
• If coronary perfusion compromised- hypoxic myocardium- sudden death

Question 13

Where is the point of maximal intensity of aortic stenosis?

Answer 13

Left base- murmur grade correlated with disease severity

Question 14

What do the follownig diagnostic tests show for aortic stenosis?
Thoracic radiograghs
ECG
Doppler echo

Answer 14

• Thoracic radiographs- unremarkalbe- aortic post-stenotic dilation sometomes
• ECG- may be unremarkable or evidence of LVE and hypertrophy, ventricular premature complexes
• Doppler
  2D subvalvular or valvular lesions, post-stenotic dilatoin
  Colour doppler shows turbulence in LV outflow
  Recording velocity of aortic outflow, diagnostic- normal velocity <1.7m/s, Velocities of >2 m/s
  Modified bernouilli can convery velocity into pressure gradient

Question 15

What is the modified bernouilli equation?
What pressure gradients show different levels of stenosis?

Answer 15

PG = 4V^2
PG < 50mmHg- mild stenosis
PG 50-80 mmHg represents moderate stenosis
PG > 80mmHg indicated the presence of severe stenosis

Question 16

With breed schemes for boxers and newfoundlands what grade of heart murmurs are allowed for breeding?

Answer 16

Boxers with no or grade 1/6 are acceptable for breeding
2/6 with echocradiography can pass if aortic velocity <2m/s

Newfoundlands- doppler aortic velocity <1.7m/s (subcostal view)

Question 17

What is the treatment/managment for aortic stenosis?

Answer 17

• No real treatment
• Betablockers may be effective- no evidence
• Arteriodilators are contraindicated- increase PG
• High pressure baloon valuloplasty have been used- no long term data

Question 18

Is pulmonic stenosis fairly common in dogs or cats?

Answer 18

Dogs

Question 19

What breeds are predisposed to pulmonic stenosis?

Answer 19

Bulldogs, boxers, bull mastiffs, cocker spaniels, west highland white, beagles

Question 20

What are the different causes of pulmonic stenosis?

Answer 20

• Usually valvular
• Type A- fused leaflets normal diameter
• Type B post-stenotic dilation, dysplastic thickened leaflets

Question 21

What does pulmonic stenosis cause?
What are the presenting signs?
What murmur is often present?

Answer 21

• Increased pressure load on the RV causes concentric RV hypertrophy
• Increases RV pressure
• Presenting signs- excercise intollerance, lethargy, asymptomatic
• Systolic ejection type holosystilic murmur most intense over pulmonic valve

Question 22

What do thoracic radiographs, ECG and Doppler echocradiohraphy show for pulmonic stenosis?

Answer 22

• Thoracic radiographs- right sided enlargment (increased sternal contact, reverse D), post-stenotic dilation of PA
• ECG- RVE and hypertrophy (deep S waves in I, II and aVF)
• Doppler- pressure overload in RV, IVS flattened/pushed to LV, valves (fused or dysplastic)
  Peak pulmonic velocity confirms the diagnosis

Question 23

How can pulmonic stenosis be treated?

Answer 23

• Treatment of severely affected usually involved balloon valvuloplasty or the pulmonic valve- more successful in type A ps
• Aim to reduce gradient by 50%
• Some bull breeds have coronary artery abnormalities- needs to be excluded
• Untreated leads to right sided congestive heart failure

Question 24

What two conditions have a similar pathophysiology to pulmonic stenosis?

Answer 24

Supravalvular stenosis- stenosis distal to pulmonic valves- frenchies
Infundibular stenosis or double-chambered right ventricle- stenosis below pulmonic valve and in infundibulum or RV

Question 25

Where are ventricular septal defects normally located?

Answer 25

Peri-membranous septum 'between' the aortic and tricuspid valve leaflets

Question 26

1. What shunt nd murmur is caused by VSD? 2. What species and breeds are presdisposed?

Answer 26

1. Left to right shunt- point of max right hemithorax 2. Most common defect in cats, not common in dogs- WHWT, cockers

Question 27

What is strange about the murmur grade of VSDs? What are the effects on the heart with VSDs?

Answer 27

Murmur grade is inverselt proprortional to the size of the defect- smaller is louder Left to right shunt- RV overloaded- pulmonary over-circulation, blood returns to LA/LV (overload)

Question 28

What do radiograhs, ECGs and Doppler echo show for VSDs?

Answer 28

Radiographs- LVE, LAE RVE, pulmonary overcirculation (increased size of lobar vessels) ECG- may be normal, or show biventricular enlargment (deep Q, tall R), left atrial enlargment (P mitrale) Echo Colour flow detects shunt Velocity is inversely proportional to the size of the defect (over 4m/s not associated with disease)

Question 29

What are the different sequelae to VSDs?

Answer 29

* In many dogs/cats not significant * Rare reports of closure * Occasionally aortic valve leaflet may prolapse into defect- aortic incompetance * Significanct left to right shunting- left sided heart failure

Question 30

How can VSD cause Eisenmenger's syndrome?

Answer 30

* With significant left to right shunt, pulmonary hypertension may develop * Pulmonary hypertension results in increased RV pressures reversing shunt * Animals with right to left shunt may become polycythaemic

Question 31

1. What breeds are predisposed to mitral valve dysplaysia? 2. How does mitral valve disease appear grossly? 3. Why can left atrial enlargment sometimes occur? 4. What is the result?

Answer 31

1. Cats and dogs- bull terriers, great danes, golden retrivers, GSD, springers 2. Mitral valve appear grossly dysplastic 3. Mitral valve can be stenotic 4. Left sided heart failure- arrythmias may result | Managed the same as MDVD

Question 32

What breeds are most commonly affected by tricuspid valve dysplasia?

Answer 32

* Can affect dogs and cats- not common * Labrodor most commonly affected * Pedigree cats more common

Question 33

1. What causes tricuspid valve dysplasia? 2. Describe the causes pathophysiology? 3. How does the murmur present? 4. What is the end effect? 5. How is it treated?

Answer 33

1. Tricuspid valve more apically displaced than normal 2. Tricupsid regurgitation, right sided volume overload 3. Right sided heart failure 4. Treatment for CHF and arrhythmias

Question 34

What are the effects of an ASD? How can it be diagnosed?

Answer 34

* Not normally haemodynamically significant * Shunting left to right Genuine defect using 2D shows a 'match stick' sign- edges of the defect are thickened and mroe echogenix

Question 35

What are the components of a tetralogy of fallot?

Answer 35

* Pulmonic stenosis * Right ventricular hypertrophy * VSD * Dextrapposed aorta

Question 36

What are the effects of the tetrallogy of fallot?

Answer 36

Pulmonic stenosis- high RV pressure Shunt from L to R when RV exceeds LV Flow from RV may exit to dextrapposed aorta straddling the VSD Animals cyanotic- fails to respond to O2 supplementation

Question 37

What is a vascular ring anomalie?

Answer 37

Persistent right 4th aortic arch- results in vascular ring surrounding oesophagus, patients show regurgitation and mega-oesophagus