CONGENITAL CARDIAC DISEASES Flashcards
pressures on left vs right side of heart
LV pressure ~120 > > > RV ~25
most common cause of a continuous heart murmur?
99% PDA
nature of a PDA heart murmur
- PMI, character
- considerations for auscultation
- 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
PDA shunt? why is the murmur continuous?
- 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
congenital left sided heart murmurs:
- which do we hear at the base?
- which at the apex?
Base:
- Aortic stenosis (systolic)
- Pulmonic stenosis (systolic)
- PDA (continuous)
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Apex:
- mitral regurgitation (systolic)
congenital right sided heart murmurs:
- which do we hear at the sternum?
- which at the apex?
Sternum:
* Ventricular septal defect (systolic)
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Apex:
* Tricuspid regurgitation (systolic)
We hear a continuous heart murmur on physical exam of a several month old puppy
- what do we suspect?
- what should we do?
- 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
PDA radiographic appearance
- 3 bumps in DV: aorta, MPA, auricle
- Distended pulmonary arteries and veins > overcirculation of pulmonary vasculature
PDA diagnostics, what they tell us, rationale
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
Patent ductus arteriosus
- blood flow, consequences
- Blood flow: LV – Ao – PDA – PA – lungs – LA – LV
- Left sided volume overload
> Can → Left sided CHF - Pulmonary overcirculation
> Can → pulmonary hypertension
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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
Ductus arteriosus - what is it anyways
- when should it close?
- 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
PDA therapy - options
- 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
ACDO Placement - how do we do it?
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
Patent Ductus Arteriosus
- common clinical presentation
- what should we do?
- Often asymptomatic
- Continuous, high grade, left sided, heart base
murmur - Do not ignore!
> Left sided volume overload → L-CHF - Closure: normal life expectancy
diagnostic test to differentite PS vs AS?
- Echocardiography
AS vs PS common locations in dogs
aorta mostly subvalvular, pulmonic usually valvular (in dogs)
AS or PS possible consequence for heart muscle
- Increased ventricular pressure:
- Concentric hypertrophy
Why might syncope occur with subvalvular aortic stenosis?
- 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
subvalvular aortic stenosis treatment, how it works
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
Presentation - AS
- who gets it?
- signs?
- physical exam?
- progression?
- prognosis?
- 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
Aortic stenosis follow-up after diagnosis?
- 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
