Congenital Cardiac Disease Flashcards
What do we mean by congenital heart disease?
- Malformations of the heart and great vessels that are present at birth
- CHD occurs due to altered or arrested embryonic development of the rudimentary heart leading to potentially gross anatomical alterations.
- Can result in significant shortage of life! These animals wont live more than 1 year or two if very bad
Does congenital heart disease have a genetic basis?
Breed predispositions to CHD suspected or proven to have a genetic basis.
Which CHD (congenital heart disease) is most common in boxers?
Aortic stenosis
Which CHD (congenital heart disease) is most common in bulldogs?
Pulmonary stenosis
When are most CHD detectable?
What is the problem with their progression?
•Most defects are detectable after birth but the severity of the haemodynamic abnormalities may change significantly during the first 6-12 months of age.
–They can get worse when they get older and they are usually at their worst when the animal is about 12 months old
–Difficulty is going to be what you do when you are presented with a 3month old dog or cat with quite a quiet murmur – what are you going to do as some will get worse!
What are innocent murmurs?
Where is their PMI?
•Innocent murmurs
–low grade I-II/VI
–PMI left heart base
–Varying intensity with heart rate
With innocent murmurs, how quickly do they resolve?
What is the problem with diagnosing innocent murmurs?
–Usually resolve by 6 months (exception some large breed dogs)
–Innocent murmur – present as quite systolic murmur loudest over heart base and may vary with HR and these may go away by the time the animal is 6 months old
–Difficulty is differentiating these innocent murmurs from pathological ones.
- If quiet systolic over heart base detected, sensible thing to do is to see animal again at 6 months and see if murmur still there.
- Most significant congenital abnormalities will have a very obvious murmur
Comparing innocent murmur versus congenital heart disease:
- What grade are they?
- Where is their PMI
- When do you hear their murmur - when is the timing?
Innocent murmur
- Grade: low grade 1-2 / 6
- PMI - Left heart base
- Timing - mid-systolic
CHD
- Grade: 2-6
- PMI - depends on condition
- Timing - depends on condition but tend to be longer in duration
Comparing innocent murmur versus congenital heart disease:
- What is their variability like?
- Does the murmur radiate, and if so - to where?
- Does it resolve?
Innocent Murmur
- Variability - varying intensity with heart rate
- Radiation - minimal
- Resolution - usually resolve by 6 months (exception some large breed dogs)
CHD
- Variability - generally non-variable
- Radiation - depends on pathology
- Resolution - no resolution
Can CHD have NO murmur associated? If so, when?
- Some significant CHD may have no murmur (large VSD shunts)
- Some small ventricular septal defects (VSD) patent ductus arteriosus may have very intense murmurs associated with only a moderate amount of shunting blood
- If a big ASD- may not have much turbulence associated, so may not always have that much of a murmur
- So difficult with congenital disease to find the bad ones! But need to differentiate the innocent murmurs
On clinical exam in dogs with CHD, what abnormalities can their be?
–arterial pulse
- Hyperkinetic pulse (waterhammer) – abnormal diastolic run off of aortic blood – Patent Ductus Arteriosis /severe aortic regurgitation
- Hypokinetic pulse – left ventricular / outflow tract obstruction – aortic stenosis or poor left ventricular output.
–Loud heart base murmur and poor pulses – tells you ventricle is having difficult pushing blood out into systemic circulation
–mucous membrane colour
- If blue, think about R to L shunting defects
- Put hands over apex, can you feel it strongly on right- maybe ventricular hypertrophy?
–Jugular veins
–Precordial impulse
If a puppy presents for a first vaccination and you hear a murmur - what is one thing you are going to chose to do to get a definitive diagnosis?
If going to chose one thing to offer the owner of an animal with a murmur, would chose to do echocardiography as will give a definitive answer
If you hear a murmur in a puppy or kitten, what should you do in practice?
–If loud (grade 3+) more likely to be a congenital anomaly, but loud does not necessarily mean bad (think small VSD)
–If < grade 2 could be innocent – re-assess at 3 and 6 months
–Can return to breeder and get money back (rarely done, bond formed)
–Ultimately one can only assess nature and severity of lesion with a full Doppler echocardiogram – will give you the answer
•Probably a referral thing if owner willing
Give a list of diagnostics you can undertake when looking at potential CHD?
- History
- Clinical examination
- Echocardiography
- ECG
- Thoracic radiographs
- Routine haematology and biochemistry
- Blood gases
- Many of these CHD cases may have multiple lesions
- Always consider referral for cases of CHD
Name the 4 most common types of CHD
- Aortic stenosis (AS)
- Patent ductus arteriosus (PDA)
- Pulmonic stenosis (PS)
- Ventricular septal defect (VSD)
What are the 3 types of aortic stenosis?
Which is the most common?
–Sub-aortic stenosis (most common one)
- Sub valvular narrowing caused by a fibrous or fibromuscular ring – spectrum of severity – might have low grade murmur at 6 weeks when we see them, then it foten gets worse as they get older and often most severe at 1 year of age
- +/- mitral dysplasia as well
- Can increase in severity as dog matures reaching maximum severity at 1-2 years of age
- Exercise / excitement can cause an increase in the intensity of the murmur
- Boxers, Newfoundlands, Golden Retrievers
–Valvular aortic stenosis (uncommon)
–Supra-valvular (rare)
How does aortic stenosis cause damage to the heart?
- Severity of the stenosis dictates the severity of the LV pressure overload and resulting concentric hypertrophy
- Myocardial ischaemia and fibrosis are common sequalae due to:
–Narrowed intramural coronary arteries
–Inadequate myocardial capillary density as the hypertrophy progresses
- These factors lead to an increased risk of ventricular arrhythmias leading to weakness, syncope, left sided congestive heart failure and sudden death
- Many animals will also have MR and AI leading to further volume overload
- Ventricular overload – concentric hypertrophy, myocardium becomes damaged as not an appropriate increase in blood supply and as a consequence get areas of ischaemia and death of muscle – commonly leads to rhythm abnormalities due to the failure of perfusion
In aortic stenosis, myocardial ischaemia and fibrosis are common sequalae due to what?
–Narrowed intramural coronary arteries
–Inadequate myocardial capillary density as the hypertrophy progresses
What are some history findings you might find out in a dog with aortic stenosis?
- Historical findings – vary from none to syncope depending on the age of the dog and severity of the lesion, the most common findings are:
- Lethargy, exertional weakness, syncope, sudden death occur in approximately 1/3 of dogs with SAS
–Will try to run around and as they cannot increase their CO appropriately, they will fall over and faint and sudden death is a risk
In this Right parasternal long axis, what is the arrow pointing to?
Can see narrowing of aortic valve – echo dense ring below the valve
Sub-arotic stenosis
In this Right Parasternal short axis view, what can you see?
Concentric LV hypertrophy
Variable echogenicity as often areas of myocardial fibrosis
In this right parasternal long axis view, what are the different coloured arrows pointing to?
Blue - Left atrium
Red - mitral valve
Yellow - narrowing below the aorta of the valve
