CONGENITAL CARDIAC DISEASES

Question 1

pressures on left vs right side of heart

Answer 1

LV pressure ~120 > > > RV ~25

Question 2

most common cause of a continuous heart murmur?

Answer 2

99% PDA

Question 3

nature of a PDA heart murmur
- PMI, character
- considerations for auscultation

Answer 3

• loudest heart base
• have to get quite cranial and sometimes dorsal to hear
• if we only listen over left apex, continuous nature of the murmur may not be audible
  > make sure you listen in various places

Question 4

PDA shunt? why is the murmur continuous?

Answer 4

• aorta to pulmonary artery, due to pressure difference
• continuous due to pressure difference existing throughout both systole and diastole > so there is always shunting between these two vessels in PDA

Question 5

congenital left sided heart murmurs:
- which do we hear at the base?
- which at the apex?

Answer 5

Base:
- Aortic stenosis (systolic)
- Pulmonic stenosis (systolic)
- PDA (continuous)
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Apex:
- mitral regurgitation (systolic)

Question 6

congenital right sided heart murmurs:
- which do we hear at the sternum?
- which at the apex?

Answer 6

Sternum:
* Ventricular septal defect (systolic)
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Apex:
* Tricuspid regurgitation (systolic)

Question 7

We hear a continuous heart murmur on physical exam of a several month old puppy
- what do we suspect?
- what should we do?

Answer 7

• PDA should close within first week to 10 days of life, so this is abnormal.
• Echo > Diagnosis, severity, tx options
• thoracic radiographs can be ok as they show overall cardiac sihouette, can look for enlarged structures of PDA. But if no resp signs, Echo is better.
• No ECG, because no arrhythmia

Question 8

PDA radiographic appearance

Answer 8

• 3 bumps in DV: aorta, MPA, auricle
• Distended pulmonary arteries and veins > overcirculation of pulmonary vasculature

Question 9

PDA diagnostics, what they tell us, rationale

Answer 9

Thoracic radiographs
* Over-circulation of pulmonary vasculature
* Dilated MPA, Ao
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Echocardiography
* PDA size and shape
> Surgical planning
* Left-sided volume overload, myocardial function

Question 10

Patent ductus arteriosus
- blood flow, consequences

Answer 10

• Blood flow: LV – Ao – PDA – PA – lungs – LA – LV
• Left sided volume overload
  > Can → Left sided CHF
• Pulmonary overcirculation
  > Can → pulmonary hypertension
  <><>
  If we get pulmonary hypertension and pressures rise enough, the shunt become less
  > But this is not a good thing! we dont want pulmonary hypertension

Question 11

Ductus arteriosus - what is it anyways
- when should it close?

Answer 11

• Required structure in-utero: Sends oxygenated blood from the RV to the systemic circulation
• Closed by 7 – 10 days of age
• Reduced smooth muscle fibres, increased elastic fibres

Question 12

PDA therapy - options

Answer 12

• Needs to be closed (the sooner the better)
• If closed, normal quality and length of life
• Interventional device closure
  > Amplatz Canine Duct Occluder (ACDO)
• Surgical closure
  > Thoracotomy, ligation

Question 13

ACDO Placement - how do we do it?

Answer 13

accessed through femoral artery
> cather passes device up descending aorta, places device across opening
> “cup” is on aorta side, flat part is on MPA side

Question 14

Patent Ductus Arteriosus
- common clinical presentation
- what should we do?

Answer 14

• Often asymptomatic
• Continuous, high grade, left sided, heart base
  murmur
• Do not ignore!
  > Left sided volume overload → L-CHF
• Closure: normal life expectancy

Question 15

diagnostic test to differentite PS vs AS?

Answer 15

• Echocardiography

Question 16

AS vs PS common locations in dogs

Answer 16

aorta mostly subvalvular, pulmonic usually valvular (in dogs)

Question 17

AS or PS possible consequence for heart muscle

Answer 17

• Increased ventricular pressure:
• Concentric hypertrophy

Question 18

Why might syncope occur with subvalvular aortic stenosis?

Answer 18

• Fixed obstruction limits cardiac output during exercise (vasodilation)
  > Tachycardia → further reduces CO
• Inadequate myocardial blood supply can → arrhythmia
  > perfusion to myocardium is reduced which leads to arrhythmias, and then synncope

Question 19

subvalvular aortic stenosis treatment, how it works

Answer 19

Beta blocker (atenolol)
* If clinical signs, ventricular hypertrophy,+/- ventricular arrhythmia
* Limits inefficient tachycardia
* Prolongs diastole (myocardial perfusion)
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NO BETA BLOCKERS IN HEART FAIILURE - we need all the stimulation we can get in such a case

Question 20

Presentation - AS
- who gets it?
- signs?
- physical exam?
- progression?
- prognosis?

Answer 20

• Large breed dogs
• Asymptomatic; exercise intolerance, syncope on
  excitement/exercise
• Left sided systolic heart base murmur
  > The higher grade, the more severe stenosis
• Subvalvular AS, progression until 18 months
• Possible outcomes (if severe):
  > Ventricular arrhythmia, sudden death
  > Left sided congestive heart failure

Question 21

Aortic stenosis follow-up after diagnosis?

Answer 21

• If dog < 18 months: recheck echocardiography when dog is > 18 months
• If worried about LV hypertrophy, myocardial function: recheck echo
• If worried about CHF: obtain radiographs
• If worried about arrhythmia: ECG
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  Not a good treatment strategy for subaortic stenosis :(
  > people will get open heart surgery to cut away the stenosis