congenital heart disease in SA Flashcards
pressure -overload
what are the causes of outflow obstruction
congenital outflow tract obstruction
- pulmonic stenosis
- sub-aortic stenosis
high afterload
combo of both
what is pressure overload
- consequence of outflow tract obstruction: (sub-) valvular stenosis
- increased reistance to the ventricular systolic outflow
- proportionate increase in ventricular pressure if flow remains constant
- pressure = flow x resistance
- increased wall stress leads to increased ventricular muscle mass (hypertrophy) - eccentric
what are the clinical signs due to outflow tract obstruction
- secondary to ventricular hypertrophy leads to reduced ventricular filling capacity
- during exercise when heart rate is high, the filling is even more impaired
- when cardiac output drops to a critical amount, cerebral hypoperfusion ensues (weakness or fainting)
- ventricular or atrial arrhythmias due to ischemic scars in myocardium (fainting, sudden death)
what is pulmonic stenosis
a dynamic or fixed anatomic obstruction to flow from the right ventricle to the pulmonary arterial vasculature
what breeds are predisposed to pulmonic stenosis
- bullmastif
- beagle
- bulldog
- spaniel
- keeshond
- schnauzer
- chihuahua
- terrier breed
what can pulmonic stenosis be due to
- isolated valvular (majority) obstruction
- subvalvular obstruction
- suprevalvular obstruction
- may be found in association with more complicated congenital heart disorders
what is type A valvular stenosis
lack of division of valve leaflets (fusion)
normal dimension of annulus
what is type B valvular stenosis
hypoplastic valve annulus and thickened leaflets
what is coronary malformation
- engl. bulldog
- aberrant left coronary artery encircles PA-causing narrowing
what are the clinical signs of PS
- none: diagnosis incidental during puppy well visit
- exercise intolerance
- syncope
what are the physical exam findings of patient with PS
- systolic murmur 4-6/6 loudest over left 3rd ICS
- arterial pulses: normal
- mucous membranes: pink
- ascites (rare)
what are the 3 diseases that can be associated with a systolic ejection murmur that is diamond shaped
- aortic stenosis
- pulmonic stenosis
- ventricular septal defect
what are the characteristics of PS on chest x-ray
- “reverse D” due to enlargement of the right ventricle (hypertrophy from chronic pressure overload)
- enlarge PA (post stenotic bulge)
what diagnostic plan provides a definitive diagnosis for PS
echocardiography
what are characteristics of PS on echo
- RV hypertrophy and dilation
- fused or thickened and relatively immobile pulmonic valve cusps
- turbulent blood flow across the stenosis
- post stenotic pulmonary artery dilation
PS
what does doppler allow us to estimate
- intra-cardiac pressure
- calculation of pressure difference (gradient) between the right ventricle and pulmonary artery
what is the Bernoulli equation
pressure gradient: 4 x velocity^2
how is the velocity of blood flow across the stenosis measured
by echo and used to asses the severity of disease
what are characteristics of PS using angiography
contrast
- hypertrophy of RV walls
- post-stenotic dilation of the main pulmonary artery
- filling defect at level of pulmonary valves
what is the prognosis of PS
- mild (0-50mmHg) - may need no intervention, good long term prognosis
- moderate (50-85mmHg) - may or may not need valvuloplasty
- severe (>85mmHg) - baloon dilation valvuloplasty -or for moderate with more than mild TR or R-L atrial shunt
how to tx PS
- beta blocker therapy (atenolol) to decrease HR during excercise and reduce RV hypertrophy; reduce myocardial O2 consumption
- baloon valvuloplasty
what is pulmonic stenosis coronary anomaly
- engl. bulldogs and some boxers may have an anamolous left main coronary artery arising from a single right coronary artery associated with the stenosis
- associated with an increased risk of balloon valvuloplasty b/c of the risk of avulsion of the left coronary artery during insufflation of the balloon and subsequent rupture of the left coronary
what is breeding advice for PS
- affected individuals and their parents should not be used for breeding
- siblings should only be used after careful screening
- if any affected offspring are born, breeding of the parents should be discontinued
key points
PS most commonly occurs due to:
- commissural fusion
- dysplasia of valve leaflets
key points
what type of murmur is heard with PS and where is it located
- loud systolic ejection murmur
- left base of the heart
key points
how is the difinitive diagnosis of PS achieved
echo
key points
when should balloon valvuloplasty be considered with PS
in moderate to severe cases
what is subaortic/aortic stenosis (SAS/AS)
- 1st or 2nd most common defect in dogs
- subvalvular > valvular > supravalvular
- breed predisposition: golden retriever, newfoundland, boxer, german shepard, rottweiler, bull terrier, bloodhound
what is subvalvular aortic stenosis
ridge
- ridge and may not be apparent at birthbut may become more obvious between 4 and 12 months of age
- ridge increases “work” of heart and causes permanent damage to muscle
what are the clinical signs of SAS
- none: diagnosis incidental during puppy well visit
- or exercise intolerance, syncope, sudden death
what are the PE findings with SAS
- systolic murmur 1-6/6 loudest over left 3rd or 4th ICS, may radiate to right side and up carotid arteries
- murmur appears/increases until 1 yr old
- femoral pulses can be weak if stenosis is severe
what diagnostic plan to use for a definitive diagnosis or AS
echocardiography
characteristics of AS on echo
- may demonstrate LV hypertrophy
- subaortic ridge or ring may be visible
- turbulent blood flow across the stenosis
- may observe post-stenotic aortic buldge
what is the prognosis of SAS
- mild (<50mmHg): no innervention needed, good prognosis
- moderate (50-80): likely normal
- servere (80-130): survival: 2.8 years vs 8.3 yrs if gradient less than <133
- servere SAS (>130): 2.8yrs, high risk for sudden death in the first 3 yrs of life - 70% mortality
what are 3 complications of SAS
- sudden death
- infective endocarditis of the aortic valve
- congestive heart failure (usually late in life)
what is the medical management of SAS
beta blockers
- HR reduction: reduce myocardial O2 consumption
- suppress arrhythmias
- but no benefits on survival shown
what are the interventional options for management of SAS
- subvalvular ridge is not as amendable to standard balloon dilation
- cutting balloon
what is PDA
smooth muscle hypoplasia in ductus - failure of ductus to close
what does PDA result in
significant shunting of blood from the descending aorta to the pulmonary artery (left to right)
what breeds are predisposed to PDA
- small dogs (bichon, chihuahua, small mixed, yorkie, poodle, etc)
- german shepard, newphoundland, boxer, bullmastif, etc
- females > males
what is the clinical presentation of PDA
- 75% cases are asymptomatic
- 25% - coughing, exercise intolerance (CHF)
what are the PE findings of PDA
- continous murmur
- loudest over left heart base
- systolic and diastolic aortic pressures normally exceed pulmonary artery presssures, shunting is continuous throughout cardiac cycle
what type of pulses are found with PDA
bounding femoral pulses
how to definitively diagnose PDA
echo
what are the characteristics of PDA on rads
- cardiomegaly: LA and LV
- pulmonary over-circulation (increased size of lobar vessels - arteries and veins) and increased vascularity
what is the management of PDA
- ductus should be closed to stop volume overload: prevent heart failure
- minimally invasive (catheter based) - ACDO, coil embolization
- surgical ligation (toy breeds and german shepards)
