Cardiovascular Flashcards
What are the non-cardiac signs of cardiac disease?
Reduced production (around 25%) Exercise intolerance Increased urine output Syncope (eg patent ductus arteriosus) Poor appetite when failing
Where is best to test perfusion in a farm animal?
Ears
not legs if lying down- will feel warmer
Why might a farm animal have pale mucous membranes?
Anaemia:
Deficiencies - Iron, copper, cobalt
Toxicities - Kale, nitrate/nitrite, molybdenum
Blood / Protein loss:
Haemonchosis
Fascioliasis
Johnes Disease
Sucking Lice
PGE
Redwater (Babesia)
Leptospirosis (acute)
Poor Perfusion:
Shock (Right Displaced Abomasum)
Heart Failure
ThrombosisWhy might a farm animal have red mucous membranes?
Toxaemia Salmomellosis (brick red) Pasturellosis Malignant Catarrhal Fever Infectious Bovine Kerato-conjuctivitis (if co-grazing with sheep) Infectious Bovine Rhinotracheitis
Why might a farm animal have blue mucous membranes (cyanosis)?
Respiratory Failure
Nitrate/Nitrite, Metaldehyde (slug pellets) poisoning (should not be grazed during/immediately after fertilisation of fields)
Congenital cardiac abnormality - Calves (insufficient oxygen circulation)
Why might a farm animal have yellow mucous membranes (jaundice)?
Hepatitis
Haemolytic Anaemia (Babesia – Red Water)
Photosensitisation (from ingesting certain plants)
Ragwort, Kale, Lupin, Copper poisoning (due to over-supplementation)
Post-partum haemoglobinuria
Leptospirosis (abortion)
Why might a farm animal have haemorrhagic mucous membranes?
Anthrax Bracken Sweet vernal grass poisoning Copper toxicity (acute) Leptospirosis Mycotoxicosis (live yeast binds to walls of mycotoxins)
Where can you feel for a pulse in cattle?
Middle Coccygeal artery 10cm below anus
External maxillary artery
Medial artery, inside forelimb - arterial sample
Caudal auricular artery
What should a cow’s heart rate be?
Calves 100 - 120
Cattle 50 – 80, high yielders up to 95
(120+ suggestive of primary cardiac disease)
Under what circumstance are the jugular and subcutaneous abdominal (milk) veins distended?
When is there increased venous pressure?
Right-sided heart failure
Cardiac failure
When is it normal to feel a jugular pulse?
When is it abnormal?
Normal up to 1/3rd way up
Occlude or empty jugular to check if abnormal
All the way up in :
Endocarditis, Pericarditis, haemothorax, hydrothorax, congestive heart failure, valvular stenosis or insufficiency
Sporadic bovine leukosis - Thymic form
Enzootic bovine leukosis - Cardiac form
In a cow, where are the base and apex of the heart located?
Base - 3rd to 6th rib
Apex - 6th rib at articulation of rib to sternum, 2 cm cranial to diaphragm
Regarding farm animals, why might the first and second heart sounds be loud?
1st sound loud if increased force of contraction
2nd sound loud if increased pressure in vessels
How does endocarditis occur in cows?
Persistent bacteraemia e.g. after traumatic reticulitis, nephritis, metritis, mastitis
Caudal vena cava thrombosis is secondary to what?
Where does the thrombosis occur?
Liver abscesses
Occurs between liver and right atrium
Why is it important that cattle and sheep get enough Vit E and selenium?
Vitamin E and selenium-containing enzymes are required as physiological antagonists of free radicals. In the absence of Vit E and/or
selenium, cellular membranes are modified by free radicals and their ability to maintain essential differential gradients for one or more ions is reduced.
What is fractional shortening?
Way of measuring left ventricle performance
Measures and ratios the change in the diameter of the left ventricle between the contracted and relaxed states
LV end-diastolic diameter - LV end-systolic diameter
/ LV end-diastolic diameter
What is a normal value for fractional shortening?
Normal > 25%
How do you calculate ejection fraction?
End diastolic volume - end systolic volume
/ end diastolic volume X 100%
Normal >50%
When scanning the heart, which view is referred to as the ‘home view’?
RPS (right parasternal) long axis 4 chamber view
End of diastole occurs where on an eCG?
Start of QRS complex
End of systole occurs where on an eCG?
End of T wave
Describe how you find the heart when doing an eCG?
Lay animal on its side on an echo table
Clip the hair over the heart, use ultrasound coupling gel for acoustic contact
Imagining can not be carried out through bone or air, so eCG must be carried out through windows between lung lobes
Minimise air-filled lungs by scanning through the lower chest wall through a hole in the echo table
Sector transducers are used to get between ribs and lungs lobes
In an ECG, what is assessed in a RPS long axis view?
Left ventricle shape
Contractility
Mitral valve, colour flow shows whether there is any mitral regurgitation
Can calculate ejection fraction
Atrial septum: left heart failure- may bulge to the right due to high left atrial pressure, vice versa
In an ECG, what can be seen in a RPS 5 chamber view?
Left and right ventricle, left and right atria, aorta
In an ECG, what is assessed in a RPS 5 chamber view?
Abnormalities of the aortic valves or left ventricular outflow
Colour flow can be used to look for turbulence here due to aortic stenosis or regurgitation
Colour flow can be used to assess the septum for a ventricular septal defect
On an ECG, the P wave represents what?
Atrial depolarisation
On a mitral valve M-mode graph, what do the E and A peaks represent?
A peak: atrial contraction
E peak: early passive diastolic filling
What is EPSS?
What is its normal value?
E-point septal separation
Distance from the anterior mitral valve leaflet to the ventricular septum in early diastole
When does the mitral EPSS (e-point septal separation) increase?
Left ventricular dilation
Rounding of the left ventricle
Poor stroke volume
Regarding ECG, which view can be used to obtain aortic velocities?
Subcostal
What is Doppler echocardiography?
The Doppler effect is noted when sound waves are transmitted and reflected off a moving target ie RBCs
Velocities are only accurately measured when the ultrasound beam is parallel with the direction of blood movement
How do you calculate the pressure gradient between two cardiac chambers?
PG= 4 x (v squared)
v: velocity
PG: mmHg
Where is the AV node located?
Above tricuspid valve
What is the function of the Purkinje fibres?
Ensure synchronous contraction of myocardium
On an ECG, the QRS complex represents what?
Conduction through bundle of his and ventricles
On an ECG, the t wave represents what?
Repolarisation of ventricles
What recumbency should a dog be in when having an ECG?
Right lateral recumbency
Lead one shows depolarisation in which direction? (ECG)
Most depolarisation is from right to left as heart lies slightly to left and left muscle mass is greater
What angle should lead 2 be at? (ECG)
Parallel to position of heart in chest
What is DCM?
Dilated cardiomyopathy
How do you calculate index of sphericity?
Assessment of rounding of left ventricle
Left ventricular length (diastole) / left ventricular width (Μ-mode)
Normal > 1.7
Give the grading scale for severity of aortic and pulmonic stenosis
0-40 mmHg = mild
40-80 mmHg = moderate
>80 mmHg = severe
What is the normal pressure in the aorta?
120/80 mmHg
Which worm species can be found in the heart?
Dirofilarias Worms seen in right atrium Cause pulmonary hypertension and thromboembolism -> pressure overload on right ventricle Right sided congestive heart failure Need to extract worms via jugular vein
Define heart failure
A clinical syndrome caused by heart disease, resulting in systolic and/or diastolic function severe enough to overwhelm the normal compensatory mechanisms, resulting in poor cardiac output with reduced peripheral perfusion and/ or elevated filling pressures, causing oedema or effusions
Describe congestive heart failure
Backwards
Associated with elevated filling pressures and extravasation of fluid (eg pulmonary oedema)
What is preload?
Venous return to the heart
Influences the degree of end-diastolic stretch on cardiomyocytes prior to contraction
What is afterload?
The resistance to ventricular ejection during systole
Why should you always do a subjective examination before a physical one when assessing a farm animal with cardiovascular problems?
Chasing an eg calf around could do more harm than good and lead to syncope
What are the major consequences of congestive heart failure?
Oedema and effusions
Peripheral vasocontriction
Tachycardia/ arrhythmias
Remodelling and fibrosis of myocardium
Fall in blood pressure due to low cardiac output causes baroreceptors to do what to sympathetic drive?
Increase sympathetic drive
Cardiac B1 adrenoreceptors -> increase heart rate to increase cardiac output
B1 receptors on Juxtaglomerular apparatus of nephron results in renin release -> activates RAAS
A1 adrenoreceptors on vascular smooth muscle cells -> vasoconstriction to increase blood pressure, and increase venous return (preload) to the heart
How does the RAAS result in vasocontriction?
Angiotensinogen -> angiotensin I (via renin, in the liver)
Angiotensin I -> angiotensin II (via ACE- angiotensin converting enzyme)
Angiotensin II -> vasocontriction
What causes the release of renin from the JGA (juxtaglomerular apparatus)?
B1 receptor stimulation
Reduced kidney perfusion
Reduced sodium concentration
What are the effects of angiotensin II?
Potent vasoconstrictor
Stimulates aldosterone release from Zona glomerulosa of adrenal cortex
Potentiated sympathetic activity
Causes vasopressin release (ADH; antidiuretic hormone) from posterior pituitary
Effects on cardiomyocytes resulting in hypertrophy and fibrosis (myocardial remodelling)
What are the effects of aldosterone?
Acts on distal convoluted tubule of nephron -> sodium and water retention
What is the effect of vasopressin?
Anti diuretic hormone
Causes water retention
Which peptides are released in heart failure?
ANP (atrial natriuretic peptide): released due to atrial stretch
BNP (brain natriuretic peptide): released due to increased left ventricular pressures
Cause diuresis, vasodialtion, natriuresis (excretion of sodium in urine) (opposite to angiotensin II)
What is natriuresis?
Excretion of sodium in urine
How can you diagnose heart failure?
Test for ANP and BNP
How do you calculate wall stress of the heart?
Radius x pressure
/ 2xwall thickness
Describe volume overload in the heart
One or more chambers encounter an increased volume of blood -> chamber dilation and compensatory (eccentric) hypertrophy, thus retaining relative wall thickness
Give some situations that may result in volume overload of the heart
Mitral regurgitation (volume overload of LA and LV) Tricuspid regurgitation (volume overload of RA and RV) Ventricular septal defect (volume overload of RV, LA, LV)
What is pressure overload?
Increased resistance to outflow of blood from a particular heart chamber -> concentric hypertrophy -> relative wall thickness increases (as chambers don’t dilate)
What is concentric hypertrophy?
Increased thickness of ventricular wall due to replication of sarcomeres in parallel
Give some causes of pressure overload in the heart
Aortic stenosis
Systemic hypertension
Pulmonic stenosis
Pulmonary hypertension
Describe the ‘La Place’ relationship
Wall tension (T) is proportional to intraventricular pressure (P) and ventricular radius (r) Therefore a dilated ventricle will increase the thickness of its wall to produce the same intraventricular pressure (adaptive remodelling)
Describe left sided backwards congestive heart failure
Elevated filling pressures in left side of heart -> transmitted back to pulmonary vasculature -> fluid leaves pulmonary venous circulation and capillaries -> pulmonary oedema -> stiff lungs -> tachypnoea or dyspnoea
Life threatening
Describe right sided backwards congestive heart failure
Increased right sided heart filling pressures -> transmitted back to great veins -> jugular veins may be distended and show jugular pulsations more cranial than just the thoracic inlet
Also affects venous return from liver -> hepatomegaly -> hepatic sinusoids may leak fluid and proteins into abdominal cavity (ascites)
Positive hepatojugular reflex may be present (distension of jugular cased by applying firm pressure over liver)
Any fluid leaking into the pleural space may overwhelm the pleural lymphatic system -> pleural effusion
What drug would you give to counteract oedema and effusions?
Diuretics esp loop diuretics eg Furosemide
Furosemide: 0.5-2mg/kg every 8/12 hours orally
If pulmonary oedema is life-threatening: give IV at 1-2mg boluses
Why should you monitor renal function and electrolytes in dogs being treated with furosemide?
Furosemide will often result in pre-renal azotaemia (increase in urea over creatinine) and hypokalaemia
The chronic oral total daily dose of furosemide should not exceed what?
8 mg/kg
Spironolactone is what kind of diuretic?
Potassium sparing
Antagonises aldosterone
How should you drain a pleural effusion?
Thoracocentesis
Should you drain an abdominal effusion?
No, unless patient is uncomfortable or breathing is compromised
Will be reabsorbed instead
What is meant by cardiac tamponade?
Compression of the heart by an accumulation of fluid in the pericardial sac
In an animal with pericardial effusion (cardiac tamponade), what should be done prior to pericardiocentesis?
Intravenous fluids, to augment preload
Give some reasons for diuretic resistance
NSAID administration
Impaired absorption of orally administered diuretic (in cases of right sided heart failure, with ascites and bowl oedema)
Chronic diuretic use can lead to distal nephron tubular cell hypertrophy with increased sodium absorption (genuine diuretic resistance)
Why might you use ACE inhibitors to treat congestive heart failure?
They are vasodilators
Reduce release of aldosterone, thus counteracting sodium and water retention
They prevent angiotensin II mediated myocardial fibrosis and remodelling
They reduce release of vasopressin (antidiuretic hormone)
Give an example of an ACE inhibitor licensed in dogs for treating congestive heart failure
Benazepril (Fortekor)
Imidapril (Prilium)
Give an example of an aldosterone- antagonist used in congestive heart failure
Spironolactone
How can you reduce workload in a failing heart?
Arteriodilators: reduce mean arterial pressure, thus reducing the resistance against which the failing left ventricle has to pump (afterload reducers). Reduces wall stress and myocardial oxygen consumption
Venodilators divert blood away from the cardiopulmonary circulation, reducing preload and left sided filling pressures, and alleviating pulmonary oedema
ACE inhibitors are balanced vasodilators (affect both arteries and veins)
Give some causes of mitral regurgitation
Myxomatous degenerative disease (weakening of connective tissue)
Ruptured Chordae tendinae
What do positive inotropes do?
Give an example
Increase contractility of the heart by increasing sensitivity of the contractile apparatus to intracellular calcium
Eg Pimobendan, give on an empty stomach, 0.2-9.6mg/kg split over two doses daily and orally
What is the main function of Digoxin?
Anti-arrythmic drug
Decreases heart rate (negative chronotrope)
Also used in patients with sinus tachycardia and reduced systolic function (poor contractility)
Enhances vagal tone and reduces sympathetic drive by direct stimulation of CNS vagal centres, and sensitises baroreceptors to blood pressure changes
Warning- can be toxic if dose too high
The standard ‘quadruple’ therapy of congestive heart failure in dogs consists of what?
Furosemide (loop diuretic)
ACE inhibitor (inhibit angiotensin II, lowers blood pressure)
Pimobendan (positive inotrope)
Spironolactone (diuretic, reduces aldosterone)
What should the minimal therapy for congestive heart failure in dogs bed?
Furosemide (loop diuretic) and Pimobendan (positive inotrope)
Which structure acts as the pacemaker for the heart?
Sinoatrial node
The QRS complex on an ECG represents what?
Ventricular depolarisation
On an ECG, what does the P-R interval represent?
Conduction through the atria and AV node
Wave of depolarisation slows from SAN to AV node (from 1m/s to 0.1m/s)
When doing an ECG, which colour leads are place where?
Red= RF Yellow= LF Green= LH Black= RH (Earth)
On an ECG, what does lead 1 measure?
Changes in electrical potential difference between right fore (-ve electrode) and left fore (+ve electrode)
Sinus arrest/arrythmias indicate what?
High vagal tone (normal in dogs with healthy hearts eg Brachycephalic breeds; not normal in cats)
Only occur at normal heart rates, never fast rates
Sinus arrhythmia occurs during a breathing cycle: R-R interval decreases during inspiration, and increases during expiration
What is a junctional escape beat?
A delayed heartbeat originating not from the atrium but from an ectopic focus somewhere in the AV junction. It occurs when the rate of depolarization of the sinoatrial node falls below the rate of the atrioventricular node.
May also occur when the electrical impulses from the SA node fail to reach the AV node because of SA or AV block.
It is a protective mechanism for the heart, to compensate for the SA node no longer handling the pacemaking activity
What is sick sinus syndrome?
Group of arrhythmias caused by a malfunction of the Sinoatrial node
WHWT
What do you give to dogs with ventricular tachycardia?
IV lidocaine
Give some systemic causes of ventricular pre studs complexes
Gastric dilation volvulus Splenic lesions Sepsis Pacreatitus Pyometra
Atrial fibrillation is more common in which breeds?
Giant breed dogs and horses
Strongly associated with atrial stretch (dogs)’
What do the following represent? Prolonged p wave Tall p wave Tall r wave Prolonged QRS
Prolonged p wave (p mitrale): left atrial enlargement
Tall p wave (p pulmonale): right atrial enlargement
Tall r wave: left ventricular enlargement
Prolonged QRS: left ventricular enlargement/hypertrophy
In an ECG, what does lead II measure?
Changes in electrical potential difference between right fore (-ve electrode) and left hind (+ve electrode)
On an ECG, what does lead III measure?
Changes in electrical potential difference between left fore (-ve electrode) and left hind (+ve electrode)
Why is lead II usually favoured when doing an ECG?
Roughly parallels the position of the heart in the chest and left ventricle
It also shows the largest QRS complex so is easier to interpret
What should you look at regarding an ECG?
What is the heart rate?
Is the P:QRS ratio 1:1 (is is there a p wave for every qrs complex, and a qrs complex for every p wave)?
What is the predominant rhythm? (Any dysrhythmias? Are p waves regular? Are QRS complexes regular: narrow is normal, wide means they originate from the ventricle rather than above the Bundle of His)
Measurements of p waves etc to make sure they are normal for that breed
What is sinus tachycardia?
Normal ECG with a heart rate faster than normal for the species
May indicate high sympathetic drive (stress, excitement, exercise etc)
What is sinus bradycardia?
Normal ECG with a heart rate slower than normal for the species
May indicate a very relaxed animal (eg sleep) or hypothermia
Describe a first degree AV block
The P:QRS ratio remains 1:1, but the P-R interval is longer than normal for the species (eg > 0.13 seconds in dogs)
May be due to high vagal tone, effect of certain drugs (eg digoxin) or disease
How long should the P-R interval be in dogs?
0.06-0.13 seconds
Describe a second degree AV block
Some p waves not followed by a QRS complex (ie P:QRS ratio > 1:1)
Mobitz type 1: normal in horses, not normal in dog- associated with high vagal tone (also called Wenckebach phenomenon)
Mobitz type 2: constant P-R interval, fixed ratio of P:QRS
Describe a third degree AV block
P wave bears no relationship to the QRS complexes
QRS complexes arise due to slower automaticity of the purkinje system/ventricular myocardium; they are wide, bizarre and have oppositely directed t wave. As they are ‘rescuing’ the heart, they are called ventricular escape complexes
Third degree AV blocks always represent disease of conduction system
Describe atrial fibrillation
If the atria are sufficiently large or stretched due to cardiac disease, coordinated cell-cell conduction (representing the p wave) is lost. They are many irregular circuses of depolarisation in the atria, some of which randomly hit the AV node and are conducted to the ventricles.
Normal QRS complexes and t waves, no p waves, fast rate with variable R-R intervals
What is a Supraventricular premature complex?
If an ectopic focus in the atria or atrioventricular junction depolarises the atria prematurely (before the SAN depolarises), a premature complex with the appearance of a normal QRS complex is produced. P wave may be abnormal or missing
What is a ventricular premature complex?
Ectopic focus arises in the ventricular myocardium, resulting in an extra heartbeat that begins in the ventricles
Wide QRS complex
T wave is in opposite direction
What should you look for when doing a subjective view of a cow when assessing cardiovascular system?
Undisturbed then after handling (handling may cause stress)
Condition score
Visible oedema? (Inter-mandibular, brisket, in front of udder)
Posture
Respiratory effort (eg when walking as a group, if at back but not lame)
A cow may have distended veins in the mucous membranes during which kind of heart failure?
Right-sided
Increased pulse amplitude in a cow is indicative of what?
What about decreased?
Increased= aortic valve incompetence Decreased= myocardial weakness, shock, toxaemia
What do the heart sounds ‘lub’ ‘dup’ represent?
Lub= ventricular contraction and A-V valve closure Dup= closure of aortic/pulmonary valves closing
Which third heart sound may be heard in farm animals?
Atrial contraction
Besides a heart murmur, what other signs would you see in a cow with endocarditis?
Persistent fever, pain on pinch test, HR 100+, shifting polyarthritis due to emboli, pulsation of mammary veins
Give some examples of bacteria that may cause endocarditis and pericarditis in cows
Mycoplasma, e.coli, streptococci, staphylococci, mannheimia
Give some examples of congenital causes oh heart murmurs in calves
Patent ductus arteriosus: blood still passes from pulmonary artery to aorta
Aortic stenosis: persistent right aortic arch, milk regurgitation
Patent Foramen ovale: blood shift from right to left atria
Ventricular septal defects: systolic murmur
Tetralogy of Fallot
Give some causes of heart murmurs in cattle
Endocarditis Anaemia Myocardial weakness (septicaemia, infection, nutritional deficiency, poisoning) Congenital (eg patent ductus arteriosus) Diaphragmatic hernia Ruminal TYMPANY
How can you test for pericarditis in a cow?
What clinical signs might a cow show?
Grunt or Eric Williams test (tests rumen and reticulum function)
Withers pinch
Shallow abdominal breathing, abducted elbows
Give some clinical signs of dilated cardiomyopathy in cattle
Peripheral oedema Jugular distension Fluid accumulation in body cavities Enlargement of heart with 'globe' shape Dilated ventricles
How can you treat cardiac-induced oedema in cattle?
Furosemide (loop diuretic)
Which associated signs are seen with myocardial degeneration in cattle and sheep?
Fever
Anaemia
Toxaemia
Give some causes of myocardial necrosis in farm animals
Infectious diseases: histophilus somni, clostridial infections, high mortality foot and mouth disease in neonates
Non-infectious: vitamin E and selenium-responsive syndrome, porcine stress syndrome, iron toxicity in piglets
Describe vitamin E and selenium-responsive syndrome
A nutritional myopathy found in calves, lambs and pigs
Also known as white muscle disease, stiff lamb disease, mulberry heart disease (pigs), nutritional muscular dystrophy
Causes myocardial degeneration and necrosis, sudden death in newborn calves
Give some differential diagnoses for sudden death in calves
Hypocalcaemia Electrocution Haemorrhage (calving injury, abomasal ulceration) Plant toxicity Hypomagnesaemia Toxaemia Bloat Anthrax Vitamin E selenium -responsive syndrome
When taking a radiograph to assess the heart, why should you always take one in dorsoventral recumbency first?
If animal is in lateral recumbency, lung can collapse and cardiac silhouette can shift from being midline to lateral
Why may a radiograph show increased opacity (more white)?
Increased fluid/cells (eg pneumonia, pyothorax)
Loss of air
What is the difference between pleural effusion and pneumothorax?
Pleural effusion: fluid in pleural space around and displacing lungs
Pneumothorax: air within pleural space (retraction of lungs from thoracic margins, elevation of cardiac silhouette from sternum)
What is emphysema?
Difficulty in expelling air from lungs, making breathing difficult
Usually secondary to other lung disease
Alveolar emphysema: abnormal permanent enlargement of alveoli
Interstitial emphysema: air within supporting connective tissue of lung
Give some causes of decreased opacity of lungs
Basic mechanisms= increased gas or decreased fluid/soft tissue Emphysema Pneumothorax Hypovolaemia Hyperinflation
Give some reasons why you might see a bronchial pattern in a radiograph?
Calcification (increased opacity; whiteness) Chronic bronchitis (allergic, irritant, parasitic, idiopathic) Peribronchial cuffing (oedema, pneumonia, PIE-pulmonary infiltrate with eosinophils)
What is bronchiectasis?
Increased bronchial width
When might you see an alveolar pattern on a radiograph?
When cells +/- fluid replaces air in alveoli. Increased opacity (whiteness)
Eg pneumonia, haemorrhage, oedema, atelectasis
Which structures are present within the cardiac silhouette?
Heart
Pericardial contents
Pericardium
What is the outcome of forward heart failure?
Reduced cardiac output
What is the outcome of backwards heart failure?
Right sided: vena caval congestion -> hepatic congestion, ascites, pleural effusion
Left sided: pulmonary venous congestion -> pulmonary oedema
How do you calculate vertebral heart score using a radiograph?
Use calipers to measure the longest axis of the cardiac silhouette. Transfer this measurement to the vertebrae and count the number of vertebrae (from T4) that fall within the caliper points.
Do the same for the short axis of the cardiac silhouette.
Add the two values together.
Should be within 8.7-10.7 for dogs, 7.5 +/- 0.3 for cats
What would you see on a radiograph of a heart with right sided disease?
Increase in cardiac width and rounding of right (cranial) side of heart
Increased right: left ratio
Increased sternal contact (?)
What might you see on a radiograph of a dog with persistent right aortic arch?
Ventral tracheal deviation and focal megaoesophagus
Left displacement of trachea
