Term
| What are the indications for cardiac evaluation in a horse? |
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Definition
| Abnormal PE (murmur, arrhythmia, signs of CHF), decrease in performance, foals - failure to thrive; presence of heart murmur, and fever of unknown origin |
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Term
| What are the things you should be able to detect in the hands off portion of the physical exam in a horse? |
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Definition
respiratory rate and effort
body condition score
jugular distension/pulses - normal to go up to the lower 1/3 of the neck
ventral SQ edema |
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Term
| What should you be able to detect in the cardiac physical examination of a horse? |
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Definition
Mucous membranes - pink and CRT < 2 sec
Precordial palpation - palpate thrill
Palpate pulses - facial artery, metacarpal |
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Term
| What is the normal heart rate in an adult horse and a foal? |
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Definition
Adult - 24-48 bpm
Neonate - 80-120 bpm |
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Term
| What are the normal heart sounds of a horse? |
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Definition
S1 - AV valve closure
S2 - aortic/pulmonic closure
S3 - rapid ventricular filling
S4 - atrial contraction |
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Term
| True/False - soft murmurs are common in athletes and foals. |
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Definition
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Term
| What will you see with a systolic heart murmur? |
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Definition
It will be soft - < 3/6
Left base - aortic ejection murmur
Turbulence in great vessels - increased flow, large size of vessel
Right base - tricuspid regurgitation
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Term
| What will loudness of a heart murmur in a horse tell you? |
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Definition
Nothing! It may increase with exercise and can't reliably distinguish physiologic from patholgic murmurs
It also does not correlate w/the size of the defect |
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Term
| Can murmurs be soft or loud? |
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Definition
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Term
| What are the valve lesions seen in horses? |
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Definition
Acquired regurgitation - common
Congenital stenosis - rare |
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Term
| What shunts will you see in horses? |
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Definition
PDA - should be gone by 4 days of age
ASD, VSD |
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Term
| Are thoracic radiographs easy to take in horses? |
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Definition
| No you usually have to take more than one casette to get everything |
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Term
| What is electrocardiography used for in horses? |
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Definition
| To evaluate rate and rhythm disturbances |
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Term
| Where do the leads go for electrocardiography? |
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Definition
Positive lead - over left apex
Negative lead - in right jugular furrow
Ground lead - withers |
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Term
| What will you see in electrocardiography in horses? |
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Definition
QRS complex is usually predominately negative
P waves are wider - may be notched as a normal finding
Purkinje system is different from dogs and cats - ECG is not very useful for detecting cardiomegaly or axis shifts, much more expansive in horses |
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Term
| What is a very common heart arrhythmia seen in horses that is the way they manifest their increased vagal tone? |
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Definition
2nd degree AV block
No therapy is indicated for it |
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Term
| What do 3rd degree AV blocks usually require? |
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Definition
| A pacemaker. Even with a pacemaker the horse is not safe to ride - they may get wobbly and faint |
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Term
| What will you see with a sinus arrhythmia in horses? |
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Definition
It is rare compared to dogs
Occurs transiently after light exercise - they're shifting from a sympathetic state to a parasympathetic state
No clinical significance to it
Sounds irregular - keep A-fib and AV block as your differentials |
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Term
| What is the most common pathological arrhythmia in horses and what makes it different from that seen in dogs? |
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Definition
Atrial fibrillation
It is different from A fib seen in dogs because it can also be idiopathic w/no structural heart disease |
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Term
| What will you see in the two versions of atrial fibrillation in horses? |
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Definition
Lone A. Fib - no structural heart disease, heart rate usually normal, increased vagal tone - decreased AV node conduction
Pathologic A. Fib - heart rate increased when heart disease is present |
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Term
| What are the clinical signs you see with atrial fibrillation? |
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Definition
Often asymptomatic (lone A-fib, pasture pet)
May present for decreased performance - athletic horse, secondary to heart disease
May be transient - present post-exercise, then disappear
Irregular rhythm on ausculatation |
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Term
| What will you see on an ECG with atrial fibrillation? |
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Definition
Supraventricular QRS complex - narrow
No P waves
Very irregular
May see undulating baseline - can be completely flat
Normal rate (unless due to heart disease) |
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Term
| What is the goal of treatment of idiopathic A-fib? |
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Definition
Convert to normal sinus rhythm
Target therapy toward atrial myocardium |
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Term
| What is the traditional drug therapy used in treatment of lone A-fib? |
|
Definition
Quinidine
+/- digoxin - used to control HR |
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Term
| What does quinidine sulfate do? |
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Definition
| Prolongs atrial action potential refractory period and slows action potential conduction velocity. |
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Term
| How do you treat a horse w/quinidine sulfate? |
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Definition
Orally via NG tube 22 mg/kg (1g/100#) for 3 days
q2 hrs for 4-6 doses
q6 hrs thereafter
Max cumulative dose - 88-132 mg/kg
Can give intravenously - quinidine gluconate
Measure plasma levels - target is 2-5 ug/ml |
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Term
| What are the side effects of quinidine? |
|
Definition
Cardiovascular - tachycardia, arrhythmias, QRS prolongation, hypotension, sudden death possible
Gastrointestinal - colic, diarrhea, flatulence
Neurologic - depression, ataxia, seizures
Other - laminitis, nasal edema (may cause obstruction), urticaria/wheals |
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Term
| Why should you stop quinidine therapy? |
|
Definition
HR > 120 bpm
QRS duration >25% of pre-treatment value (obtain ECG prior to each dose)
Severe side effects noted |
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Term
| What is the supportive therapy used for A-fib? |
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Definition
Digoxin - if HR > 60 bpm
Lidocaine (+/- magnesium) - ventricular arrhythmias
Sodium bicarbonate - control tachyarrhythmias, increase quinidine binding to plasma proteins
Phenylephrine - hypotension |
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Term
| What is electrical cardioversion and what is it used for? |
|
Definition
It is performed under general anesthesia - for treatment of A-fib
Electrocardioversion catheters placed in the right atrium and pulmonary artery - direct current applied to resynchronize electrical activity of atrium
It is 98% efficacious vs. the 75-92% efficacious quinidine |
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Term
| What is the prognosis of A-fib? |
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Definition
Good prognosis for successful conversion if:
HR < 60 bpm - no heart disease present
A. fib present < 4 months
First occurrence - likelihood of conversion and maintenance of NSR decreases w/each recurrence
Larger, older horses may be harder to convert |
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Term
| What are isolated VPCs common with? |
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Definition
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Term
| Is ventricular tachycardia common or uncommon? |
|
Definition
|
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Term
| What is the risk associated with ventricular tachycardia? |
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Definition
|
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Term
| What can you see ventricular tachycardia with? |
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Definition
Often associated w/underlying heart disease - such as secondary to myocarditis
Can be secondary to drug therapy (i.e. quinidine) |
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Term
| What is the treatment for ventricular tachycardia in horses? |
|
Definition
Emergency treatment - Lidocaine
Chronic treatment - procainamide, magnesium, propafenone, quinidine, atenolol
Treat underlying disease |
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Term
| In what age horse will you see myxomatous valve degeneration? |
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Definition
| Older horses - aortic & mitral valves most commonly |
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Term
| Where will you hear the murmur with aortic or mitral myxomatous valve degeneration? |
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Definition
Aortic - left basilar diastolic murmur
Mitral - left apical systolic murmur |
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Term
| What determines prognosis in myxomatous valve degeneration? |
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Definition
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|
Term
| What will you see with left-sided congestive heart failure in a horse? |
|
Definition
|
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Term
| What will you see with right-sided congestive heart failure in a horse? |
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Definition
| Pleural effusion, SQ edema, and ascites |
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Term
| What is the treatment of congestive heart failure in a horse? |
|
Definition
Furosemide & Digoxin
ACE inhibitors - very expensive, short half-life, IM or IV |
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Term
| What is the prognosis for a horse with congestive heart failure? |
|
Definition
| Poor - especially for use |
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Term
| What side is endocarditis typically seen on in horses? |
|
Definition
| Left side - aortic and mitral |
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Term
| When should you suspect endocarditis? |
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Definition
| With a fever of unknown origin |
|
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Term
| What type of lesion do you see with endocarditis? |
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Definition
| It can be primary or secondary - pneumonia, sepsis, septic arthritis |
|
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Term
| How should you treat endocarditis in horses? |
|
Definition
Aggressively!!!
Long-term IV antibiotics |
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|
Term
| What is the prognosis of endocarditis in horses? |
|
Definition
Typically poor
Valve is hard to sterilize
CHF may develop |
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Term
| What are some causes of pericarditis in horses? |
|
Definition
Viral and bacterial
Immune-mediated
Idiopathic |
|
|
Term
| What does pericarditis do? |
|
Definition
| Restricts filling of the right heart |
|
|
Term
| What develops first with pericarditis? |
|
Definition
| Signs of RHF - SQ edema, jugular pulses, signs of poor cardiac output |
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|
Term
| What is the prognosis of a horse with pericarditis? |
|
Definition
|
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Term
| What is the most common congenital cardiac disease in horses? |
|
Definition
| Ventricular septal defect |
|
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Term
| What will you see if the VSD is large in horses? |
|
Definition
Left heart failure
Right-sided CHF if pulmonary hypertension develops |
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Term
| True/False - congenital VSD in horses is mostly perimembranous |
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Definition
|
|
Term
| What will you hear on auscultation of a congenital VSD in a horse? |
|
Definition
Systolic murmur
Right-sided (apical or basilar)
+/- left basilar (secondary to relative pulmonic stenosis) |
|
|
Term
| What are two common cardiotoxins found in equine medicine? |
|
Definition
White Snake Root
Ionophore toxicity |
|
|
Term
| Where will you find white snake root? |
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Definition
| In woods, damp, and shady pastures |
|
|
Term
| What is the toxic principal of white snake root? |
|
Definition
|
|
Term
| What are the cardiac signs of white snake root? |
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Definition
| Heart failure w/myocardial necrosis and fibrosis |
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|
Term
| What are the non-cadiac signs of white snake root intoxication? |
|
Definition
| Weakness, tremors, hepatic necrosis, and lipidosis |
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|
Term
| What is the treatment for white snake root? |
|
Definition
|
|
Term
|
Definition
Coccidiostat inteded for cattle or poultry
e.g. Monensin, Iasalocid, or salinomycin |
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Term
| How do most horses get ionophore toxicity? |
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Definition
| Usually from accidental feed contamination |
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Term
| What are the cardiac manifestations of ionophore toxicity? |
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Definition
Heart failure
Arrhythmias (sudden death) |
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Term
| What are the non-cardiac manifestations of ionophore toxicity? |
|
Definition
| Fever, depression, lethargy, anorexia, profuse sweating |
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|
Term
| What type of hair follicles do horses have? |
|
Definition
| Simple hair follicles - one hair per follicle |
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Term
| What is the scientific name for summer sores? |
|
Definition
|
|
Term
| What is the etiology of habronemiasis? |
|
Definition
| Habronema muscae, Draschia megastoma, or Habronema majus |
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|
Term
| What are the intermediate hosts for summer sores? |
|
Definition
House fly for H. muscae and D. megastoma
Stable fly for H. majus |
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|
Term
| What is the pathogenesis of summer sores? |
|
Definition
| Adults live in the stomach --> larvae passed in the feces --> flies carry L3 larvae to the wound (has to get in through a skin defect) |
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Term
| What are the clinical signs you will see with habronemiasis? |
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Definition
Granulomas on the eyelid, lower leg, ventrum, prepuce, urethral process
Ulcerations, contain gritty yellowish granules
+/- pruritus |
|
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Term
| What are some differentials you should keep in mind when you think you have summer sores? |
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Definition
Proud flesh, sarcoids, SCC, EGC, infectious granulomas, bacterial like Botryomycosis
Keep in mind that Habronema may be found in any of these lesions!! |
|
|
Term
| How do you diagnose habronemiasis? |
|
Definition
History and exam
Impression smears - +/- eosinophils
Deep skin scrapings - +/- larvae
Biopsy - must do this to rule out the other differentials |
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Term
| What are the mainstays to therapy of summer sores? |
|
Definition
Debulking - getting rid of the granulomatous tissues makes them resolve faster
Reduce inflammation - topical or systemic steroids
Prevent reinfection - fly sprays to prevent this from happening over and over again
Avermectins |
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|
Term
| What is the etiology of onchocerciasis? |
|
Definition
| Filarial nematode - Onchocerca cervicalis |
|
|
Term
| What is the pathogenesis of onchocerciasis? |
|
Definition
| Hypersensitivity reaction to the dead microfilaria |
|
|
Term
| What are the lesions seen with onchocerciasis? |
|
Definition
Ocular - uveitis
Erythema, crusting, scaling alopecia, depigmentation (which may or may not be permanent) |
|
|
Term
| Where do the filarial nematodes of onchocerciasis live? |
|
Definition
| In the nuchal ligament so once the horse get them it has them for life |
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|
Term
| What are you going to see with the lesions of onchocerciasis? |
|
Definition
Lesion in center of forehead "bulls-eye"
Ventral abdomen involvement
Mild to severe pruritus
May worsen in summer
May scar, or have permanent leukoderma |
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