Equine Cardiology and Respiratory Medicine: Diagnostic Approach and Cardiology Flashcards
What are some common presenting signs of LRT in horses and what could they mean?
Cough- Specific for LRT
Physical- foreign material, turbulent air, mucus
Chemical- osmolarity, irriant
physical and chemical and inflammation stimulate irritant receptors
Stimulation causes inhalation and forced expiration
Bilateral nasal discharge
Airway inflammation
increased/altered mucus
Mucopurulent discharge
Anything behind the eyes leads to bilateral
Tachypnoea/dyspnoea
hypoventilation
V/Q mismatch
impaired gas diffusion in alveolus
hypercapnia, acidaemia, hypoxaemia
What history and signalment would you want from a horse with respiratory disease?
Disease time course and features
Herd or individual problem
Age and use of horse
Managment and environment
Coexisting problems
What should be observed from a distiance when trying to diagnose LRT in horses?
Posture- extended head and neck with severe respiratory disease
Abdominal effort
RR
Respiratory Depth
Pattern
Hypertrophy of external abdominal oblique- Heave line
What should be assessed with a general clinical examination for a horse with respiratory disease?
All systems
Temp/HR
Ventral oedema
Guttural pouch/lymph nodes
Nares and nasal passages
Auscultation- treachea and triange-
How can you know whether URT or LRT collapse is more likely?
Inspiratory noise- URT
Expiratory noise- LRT
What is ‘normal breathing sounds’ in a horse?
Turbulent air in large animals
Soft blowing sound
Inspiration is louder then expiration
Faster air = louder
Low frequency sounds travel best through normal lung
What are adventitious breathing sounds?
Wheezes
Crackles
Pleural rubs
Cough
Expiratory grunt/groans
What creates a wheezing breathing sound?
What anatomical abnormalities can lead to wheezing how can they differ?
Wheeze is caused by airway narrowing and vibration
Thickened wall- oedema, inflammation
Intraluminal obstructions- mucus/foreign body
Bronchospasm
Extraluminal compression
Can be monophonic (one sound) or Polyphonic (lots of wheeze sounds
What is the bernoulli effect and why does it cause further narrowing of the airway?
- Narrowed airway causes higher velocity air created a lower pressure in bronchi
- Lower pressure causes further narrowing of the airway
LRT- most common end expiratory
URT- most common inspiratory
Shower Curtain Effect
What different crackles can be made with respiratory disease?
Coarse crackling-
bubbling mucus
Inspiration or expiration
Radiate widely
Fine crackles-
Popping open of collapsed small airways
Most common: early inspiration
What are pleural friction rubs and how can they sound?
Inflammed parietal and visceral pleural membranes rubbing together
Variable- fine crackles to sand paper rubbing together
Usually inspiration and expiration at same point in respiratory cycle
How can auscultation be done when a horse has increases RR?
Re-breathing- bag over head
Increases CO2
Increases respiratory rate and tidal volume
Increases normal and abnormal resp sounds
Cough- abnormal
What is used for thoracic percussion and what does it do?
Use fingers or pleximeter (spoon) and plexor
Checks for pinging- distension etc
What further diagnostic tests can be done after a clinical exam for respiratory disease?
- Lab and clinical pathology
- nasopharyngeal swab
- Endoscopy and transendoscopic tracheal aspirate
- Percutaneous tracheal aspirate
- Bronchoalveolar lavage
- Thoracocentesis
- Imaging- radio, ultra
- Lung biopsy
What clinical pathology can be done for diagnosis of respiratory disease?
Blood sample-
Inflammatory profile- WBC/proteins/fibrinogen/Serum amyloid A
Lactate- tissue hypoxia
Blood gas profile
PCR to idenfity agent
Paired serology
Bacterial culture/ID
Virus isolation
What can be used to directly assess the URT?
What three LRT samples can be taken?
Endoscopy- Trachea, carina
Tracheal aspirate
Bronchoalveolar lavage
Thoracocentesis
What are the different techniques of tracheal aspirate collection?
What are the adv and dis adv of each?
Transendoscopic or Transtracheal (puncture through skin)
Transendo-
Adv- easy, non-invasive, sample represenitive of whole lung
Dis- sample contaminated by nasopharyngeal flora, specialist equipement
Transtracheal-
Adv- no containation, no equip, good for foals (too small for endo)
Dis- May cough catheter into pharynx, invasive- cellulitis, subcut emphysema
How are tracheal aspirate samples analysed?
Differential cell counts-
Abnormal >20% neutrophils, presence of mast cells, eosinophils
Presence of mucus, amount, curschmann’s spirals
Gram stain- intracellular organisms
Bacterial culture/ sensitivity
Describe broncheoalveolar lavage
What is it useful for and not?
What are the Adv and Dis?
Small area of distal airway lavaged with saline, surfactant ‘washing up liquid’ is a sign of a good sample
Useful for cytology, unsuitable for bacteriology
Adv-
Sample from distal airways- more commonly affected
Best corelation with pulmonary function and histopath
Equipment cheap
Dis-
Site may not be appropriate- abscess, pneumonias
Pharyngeal contamination
Invasive
- When should BAL be performed?
- BAL v TA?
- Is LRT present- poor performance investigations, undiagnosed dull
Characteristic LRT- severe, chronic, treatment failures
Monitoiring response to treatment - BAL- better correlation with obstruction, excercise induced hypoxaemia, lung histopath
TA- bacteriology, focal lung lesions (abscess), tracheal inflammation
What is abnormal about this thoracic ultrasonography?
Pleural effusion
When is thoracocentesis indicated?
Whenever there is a pleural effusion
Increased RR
Dull thoracic percussion ventrally
Pleurodynia
Ultrasound
How can cardiac disease present in horses?
History of poor performance- depends on use
Clinical signs of cardiac failure- rare
Systemic illness- secondary heart disease
Incidental finding- vetting
What is the aim of a CV investigation?
Establish the significance of any findings-
currently and in the future, cardiac murmurs/arrythmias are common
Interprest findings according to use of the horse
What is assessed with cardiac disease in horses?
Effect of the cardiac condition on:
Athletic performance
Risk of collape
Risk of CHF
Resale value
What are the different ways of cardiac investiagation?
- Clinical exam/ auscultation
- ECG +/- excercise/24h
- Echocardiography
- Clinical pathology
- Excercise testing
What should be collected from a clinical examination for a horse with suscpected cardiac disease?
History and signalment- performance history, fitness, concurrent diseases
Systems- resp, body condition, concurrent disease
Cardiac abnormalities can be incidental or secondary
(neoplasia causing anaemia leading to murmur)
Peripheral arterial pulses- regular, strength, whilst auscultating
Pulse pressure
Jugular distension
CV system- RR, Oedema, MM, Hydration, peripheral perfusion
After a clinical exam what should be checked for with a cardiac examination?
Describe auscultation
HR
Rythm- regular, regular irregular, irregularly iregular
Pulse- quality, defecits
Murmurs
Auscultation
- Quiet, take time
- Find apex beat- mitral valve
- Move stethoscope- dorsal/cranial
- Right- pull leg forward, under triceps just dorsal to elbow point- tricupsid
How can clinical pathology be used for diagnosis of cardiac disease?
- Detecting underlying disease
- Electrolyte abnormalities
- Cardiac biomarkers
- Cardiac isoenzymes replaced by troponin- myocardial disease
- Natriuretic peptides- minimal use
What are the basic normal heart sounds in horses?
What is the normal order and period?
Where is alterial pulse palpated
Ventricles contract- S1- shutting of AV valves- mitral/tricupsid- LUB
Ventricles relax- S2- shutting of semilunar- aortic/pulmonic- DUB
Atrial contraction- S4 ‘B’- common in horses- just before S1
End of rapid ventricular filling- S3 ‘D’- less common- just after S2
Order- S4, S1, S2, S3
Systole much shorter the Diastole in normal HR
Pulse- palmar, median, great metatarsal artery
When is ECG use indicated?
Suspected non-physiological arrythmia detected
Chamber dilation onf echocardiography
Poor performance
Monitoring of patients with CVS compromise- GA
What sounds of the heart coordinate to the ECG complex?
P- atrial depolrisation/ contraction- S4- ‘B’
QRS- ventricular depolarisation/contraction- S1- ‘LUB’
T- Ventricular repolarisation- S2- DUP
Where are leads places for base apex ECG?
Record on Lead I
Red- negatvie on right arm (bottom of brachiocephalic)
Yellow- positive- left arm (behind limb on trunk)
Lellow left, red right
When is a telemertic ECG used and why?
Used for 24h and Excercise- no wired between horse and machine
Allows for excercsie and continuos assessment and therefore detection of arrythmias that may otherwise be missed
When is echocardiography indicated?
- Previously diagnosed with physiological murmur which is louder on serial examinations
- Grade 3-6 mitral/aortic valve or 4-6 tricupsid murmurs
- Any aortic regurgitation in ridden horse
- Suspected VSD or other congenital lesions
- Any continuous murmur
- Any pathological arrhythmias
- Signs of CHF
- Poor performance after musk/resp ruled out
