Small animal cardiology Flashcards
What is orthopnoea
Change in breathing related to position i.e shortness of breath when lying down
What is a cough from heart disease like compared to primary respiratory disease
Heart disease cough is softer and moister (due to some pulmonary oedema)
What is cyanosis
Blue/grey discolouration of mucous membranes due to increased quantity of deoxygenated Hb
i.e pA O2 <40mmHg, arterial saturation <70%
What does a more distended jugular vein indicate
Increased systemic venous pressure i.e higher right ventricular pressure
What type of heart failure is ascites a sign of
Right sided
Because increased pressure in right side of heart so impairment of pumping blood to the lungs
WHen might we have a decreased pulse pressure
Heart failure
Hypovolvaemia
When might we have an increased pulse pressure
Anaemia
Patent ductus arteriosus
Aortic regurgitation
What is a pulse deficit
Where a heart beat does not generate a palpable pulse e.g in some tacharrhythmias
What is the precordial impulse
Apex beat
Usually found at LIC4/5
What is the diaphragm used for hearing
High frequency sounds
What is the bell used for (stethoscope)
Low frequency sounds e.g 3rd and 4th heart sounds in a dog
What valve does the L apex beat correspond to
Mitral valve
= first heart sound
What do we hear at the base beat
Aortic and pulmonic valves; hard to differentiate them on small dogs and cats
Where do we hear the tricuspid valve
Right heart apex
When might the second heart sound be split
Pulmonary hypertension
= because high pressure in pulmonary veins means delayed closure of pulmonary valve so separated in time from closure of the aortic valve
Which heart sound becomes very dominant in stress/exercise
First heart sound (AV valve closure)
Because it is dependent on ventricular contractility
What is the third heart sound and when might we hear it
Noise from rapid ventricular filling during diastole
- get noise where there is vibration in a stiffer than normal ventricular wall e.g if it hasn’t emptied fully such as dilated cardiac myopathy
What is the fourth heart sound and when might we hear it
Occurs in atrial systole when blood is forced into an over distended ventricle e.g in feline hypertrophic cardiac myopathy
When can it be hard to distinguish extra heart sounds
In high heart rates e.g cats with HR>180
What are the two mechanisms of heart murmurs
Turbulence of blood flow
Vibration of a cardiac structure
What causes flow murmurs
Low viscosity blood
e.g in immature animals, anaemia
+ increased cardiac outflow velocity can cause it
Murmur grading system
I - heard in a quiet room
II – faint but easily heard; disseminated over larger area e.g on both sides
III – same intensity as heart sounds
IV – louder than the heart sounds
V – loud murmur plus palpable thrill
VI – heard when stethoscope removed from the chest wall
What is the loudest and most common type of murmur
Systolic
What are the systolic murmurs
AV valve regurgitation
Left to right shunting in a ventricular septal defect
Aortic stenosis
Pulmonic stenosis
How can we split up systolic murmurs into two types
Plateau murmurs: AV valve regurg, VSD
Ejection murmurs which can be squeaky: aortic stenosis, pulmonic stenosis
What are the types of diastolic murmurs
Aortic regurgitation
Pulmonic regurgitation (rarely heard; on right side)
AV valve stenosis
What can cause a continuous murmur
Patent ductur arteriosus
Combinations of systolic and diastolic murmurs
What systolic murmur would be heart loudest on left heart base
Pulmonic stenosis
Aortic stenosis
What systolic murmur would be heart best on left side over heart apex
Mitral valve regurgitation
What heart murmur would be heart best on the right side at the sternal border
Ventricular septal defect
What systolic murmur would be heard best on the right side over the mid heart
Tricuspid regurgitation
Subvalvular aortic stenosis
What diastolic murmur would be heard best on the left chest wall at the apex
Mitral valve stenosis
What diastolic murmur would be heard best on the left side at the heart base
Pulmonary valve regurgitation
Aortic valve regurgitation
What diastolic murmur would be heard best on the right side
Tricuspid stenosis
What is heart failure
State where heart is unable to maintain an adequate circulation in the face of normal filling pressures
- Clinical syndrome involves reducing of cardiac output, increased venous pressures and molecular abnormalities that cause deterioration of heart and myocardial cell death
How do Frank starling curves change in heart failure with increasing preload/afterload
- Cardiac output can’t increase much with increasing preload
- Pressure increases greatly with small increase in preload
- Stroke volume falls rapidly with any increase in afterload (arterial resistance against which left ventricle ejects blood)
What consequences are there is preload increases on the right side of the heart
Jugular distension + positive hepato-jugular reflux test
Ascites
Odema
Pleural effusion
Enlarged lvier/spleen
What is the hepato-jugular reflux test
Where pressure put on the abdomen causes jugular venous distension as blood is forced forward
See this in right sided heart disease; high preload here
What happens if preload increases in the left side of the heart
Pulmonary oedema –> hypoxaemia/cyanosis
Can lead to excessive right sided preload
Why do we get arrhythmias when there is a fall in cardiac output
Because hypoxia means low perfusion of the heart itself
Signs of fall in CO
- Cool extremities
- Fall in rectal temperature/shock
- Weakness/syncope
- Slow capillary refill time (>2 sec)
- Arrhythmias
- Reduced mentation/confusion
- Congestive failure signs usually coexist with a reduction in cardiac output
What effects does RAAS activation cause following drop in CO
Angiotensin II causes vasoconstriction
ADH also causes vasocontriction and water retension
Aldosterone causes sodium and water retention
SO get increase in afterload (from vasoconstriction) AND preload (from increased blood volume via water retention)
What are ANP and BNP and what do they do
Stored in myocardium and released when atria and stretched i.e high preload in heart disease
Natriuretics and vasorelaxants so temper RAAS system
Also reduce aldosterone secretion
Inhibit sympathetic system
Act as diagnostic markers
What happens to the heart when there is sympathetic upregulation e.g with fall in CO
Abolition of sinus arrhythmia in dog
Heart rate increases; this both increases myocardial O2 demand and reduces what it recieves by shortening diastole
How does fall in cardiac output change heart itself
Causes myocardial hypertrophy
What types of cardiomyopathy do dogs vs cats get
Dogs get dilated cardiomyopathy = sytolic failure due to failure of contractility
Cats get hypertrophic cardiomyopathy; thick stiffened heart muscle can’t relax so get failure of distole
Clinical signs of forward failure
Poor muscle perfusion means exercise intolerance
Vasoconstriction means palo
Increased symp tone causes tachycardia
Poor heart contractility gives weak pulses
Poor renal perfusion gives azotaemia
Angiotensin II release causes increased thirts
Clinical signs of left sided backwards failure (congestive heart failure)
Tachypnoea/dyspnoea due to pleural effusion or pulmonary oedema
+ resp crackles and wheezes or absence of lung noise
Cough may be harsh if from enlarged left atrium or soft if due to pulmonary oedema
Signs of right sided backwards failure
Jugular distension due to increased RA pressure
Hepatomegaly (increased vena cava pressure)
AScites
Hepatojugular reflex
PLeural effusion (because increased pressure in azygous and bronchial veins)
Peripheral oedema
Why does right sided backwards failure cause pleural effusion
BEcause it causes increased pressure in azygous and bronchial veins
Clinical classification of congestive heart failure*
1 = no signs but clinical evidence of heart disease
2 = exercise intolerance or dyspnoea after MARKED exercise
3 = marked exercise intolerance i.e dyspnoea after MILD exercise
4 = dyspnoea at rest, cannot exercise
Modified classification of heart failure
A Dogs at high risk of heart disease
B1 Murmur but no radiographic heart enlargement
B2 Murmur and chamber enlargement
C Evidence of heart failure
D Heart failure not responding to standard treatment
At B2, it is useful to intervene medically (no evidence that intervening earlier helps)
AT what point is it useful to intervene in heart failure
Stage B2
*What are the 4 phases of diastole
1: Isovolumetric relaxation; = time between aortic valve closure and mitral valve opening
2: rapid early mitral inflow
3: Diastasis: little change in ventircular volume or pressure
4: atrial contraction; contributes to ventricular filling
What things can delay heart relaxation
Ventricular hypertrophy
Abnormal calcium movement
What things can cause diastolic dysfunction
Ventricular hypertrohy
OBstruction to ventricular filling e.g neoplasia within heart
AV valve stenosis
Pericaridal disease causing tamponade
What things can cause ventricular hypertrophy
- Hypertrophic cardiomyopathy
- Aortic stenosis
- Pulmonic stenosis
- Heartworm disease
- Systemic hypertension
What is cardiac tamponade
Where pressure from outside the heart affects the filling of the inside of the heart e.g pericardial effusion
Right side is affected first because it is at lower pressure
What are the goals of therapy for heart disease and what is the therapy
1) Diuretics to control salt and water retention and relieve oedema
2) Inotropic medication to improve pump function e.g piobendane, digoxin
3) Vasodilators to reduce heart workload (afterload)
Functions of the pericardium
Prevents heart overdilation
Protects heart from infection
Maintains heart in a fixed position
Co-ordinates right and left ventricular funciton
Layers of the pericardium
Outer fibrinous layer
Inner serous; patietal and visceral layers
What happens in cardiac tamponade
Pericardial fluid accumulation means intrapericardial pressure becomes higher than that of the right heart causing collapse and impediment of venous return
This then causes increases systemic venous pressure and can lead to right sided congestive heart failure
*What are two congenital diseases of the pericardium
Peritoneopericardial diaphragmatic hernia
Benign intrapericardial cyst
What is Peritoneopericardial diaphragmatic hernia PPDH:
Where pericardial sac does not become independent from the diaphragm and abdominal cavity so abdominal organs can herniate into the pericardial sac
common in weimeraners + persians
Often incidental
Treatment is surgery
What are the most common cause of pericardial effusion in dogs
Neoplasia
Then idiopathic
Left atrial rupture
Which neoplasias can cause pericardial effusion
Haemangiosarcoma most common
Chemodectoma
Mesothelioma
Signalment of haemangiosarcoma in heart
Predilection to right atrial auricle and right atrium
Older large breed dogs e.g GSD, golden retrievers
Hgih metastatic rate
What is a chemodectoma and what are the characteristics
Heart base tumour; 2nd most common tumour of the heart
Arises from chemoreceptors in pulmonary artery and ascending aorta
Slow growing, low metastatic rate, locally invasive
Treatment = pericardiectomy
What breeds are predisposed to chemodectomas
Brachycephalics
What are mesotheliomas in the heart
= diffuse tumours arising from pleura, peritoneum and pericardium
Often large volume of pericardial effusion and rapidly recurs if drained
Treatment = pericardiectomy to relive signs and intracavity chemo
Guarded prognosis
Which breeds are predisposed to idiopathic pericardial effusion
Younger large breed dogs e.g St Bernard, GOlden Retrievers
What is the main differential for idiopathic pericardial effusion
Mesothelioma
IPE is a diagnosis of exclusion
Which dogs are predisposed to left atrial tear/rupture
Older small breed dogs since this is a complication assocaited with advanced mitral valve disease via damage from the jet
How can mitral valve disease lead to left atrial tear/rupture
- Severe left atrial enlargement
- Increased left atrial pressure causes wall over-stretching
- Mitral regurgiation causes jet lesions in atrial wall
What does a left atrial tear look like on echo
Pericardial effusion with intrapericardial thrombus inside the pericardial sac
- This clot is attached to where the tear happened and stops the bleeding
Prognosis is fair if they survive first 7 days
What is the most common cause of pericardial effusion in cats
Congestive heart failure
Presents as mild effusion withOUT cardiac tamponade
What is constrictive pericarditis
Rare condition of the pericardium where it becomes thickened/fibrotic and non-distensible
Leads to right congestive heart failure with minimal/no pericardial effusion
What is the aetiology of constrictive pericarditis + treatment
May be idiopathic, neoplastic, inflammatory
Treatment = pericardiectomy (+ do histopath)
Key clinical exam findings in a pericardial effusion case
Muffled heart sounds **
Weak femoral pulses ***
+ Tachycardia, resp signs, signs of right sided congestive heart failure, tachycardia, pulsus paradoxus
What is pulsus paradoxus
Where there is a reduction or absence of pulse on inspiration
= because of cardiac interdependence in pericardial effusion i.e only one ventricle can increase in volume at a time;
- During inspiration right side get flow due to change in intrathoracic pressure so less output from L side and weaker pulse
Two ket places to look for masses on the heart on echo
Right auricle (haemagiosarcoma)
Heart base (chemodectoma)
In which case of pericardial effusion would we not drain the fluid (pericardiocentesis)
Left atrial tear
When is pericardiectomy indicated
Recurrent pericardial effusion
Constrictive pericarditis
Palliate surgery in neoplastic effusion cases
When is pericardiocentesis essential
Cardiac tamponade cases
Which X ray views do we take of the heart by convention*
Right lateral
Dorsoventral (to avoid distorsion)
What heart phase will most X rays be taken in and what effect does this have
Diastole since this lasts longest
Makes heart bigger than if taken in systole
Normal cardiac size parameters in dogs
- Heart width <2/3 width of thorax
- Height of heart < 2/3 height of thorax
- Width of heart 2.5-3.5 IC spaces
Vertebral heart score 9.7 +/- 0.5
Cardiac size parameters in cats
Width < 2/3 width of thorax and 2-3 intercostal spaces
What does the heart look like in canine generalised cardiomegaly
Globoid with enlargement in all chambers
Signs of congestive heart failure e.g pulmonary oedema, hepatomegaly, ascites
What does heart look like in feline generalised cardiomegaly
More valentine shaped
Heart displaced to the right
What does cardiac X ray look like with left atrial enlargement
Increased heart height
Enlargement of pulmonary veins
Dorsal deviation of mainstem bronchi
Rounded soft tissue opacity visible in dorsocaudal part of lung
Radiographic signs with left ventricular enlargement
Tracheal elevation
Straight caudal border of the heart
Longer cardiac silhouette with rounding of apex on DV
Radiographic signs of right ventricular enlargement
NB = overdiagnosed; actually rare
Elevation of apex on left lateral view, elevation of trachea
Rare in isolation; often concurrent with left ventircular dilation in DCM
Radiographic signs of right atrial enlargement
Rare in isolation
Focal bulge on cranial aspect of cardiac silhouette
Deviation of trachea at focal bulge
X ray signs with pericardial effusion
Globoid shape
Sharp borders
Evidence of right sided CHD often present
Where do pericardial cysts occur
At costophrenic angles; related to trapped omentum or abnormal mesenchymal development
Presents similarly to pericardial effusino
What do peritoneo-pericardial diaphragmatic hernias look like on X ray
- Globoid or abnormally shaped cardiac silhouette
- Gas filled structures overlying cardiac silhouette
- Cardiac silhouette not of homogenous opacity
- “Empty abdomen”
- Sternebral abnormalities
- Most common in Weimaraners
What should we consider as possible causes of microcardia
Addison’s
Hypovolaemic shock
Where are artery and vein in relation to each other on DV ad lateral
DV view: artery = lateral to vein
Lateral: artery = dorsal to vein
Should be < diameter or 9th rib
What does pulmonary under-circulation look like
LUng fields more lucent
Pulmonary arteries small than normal and than the corresponding vein
Differentials for pulmonary under circulation
- Hypovolaemia e.g shock, dehydration
- R-L shunting
- Severe pulmonic stenosis
- Pulmonary thrombo-embolism
[Could also be emphysema, overinflation, overexposure]
What does pulmonary over circulation look like on x ray
Increased vascular pattern, arteries and veins larger than
Differentials for pulmonary over-circulation
- Left to right shunting
- Congestive heart failure
- Heartworm disease
- Iatrogenic fluid overload
Also could be: underexposure, expiratory radiograph
Modified bernouli equation
Pressure gradient = 4 X (maximum velocity)^2
