Equine Dysrythmias Flashcards
How do myocardial disease and endocardial disease differ in how they manifest?
- Endocardial disease
- Valvular regurgitation, Jet lesions
- MANIFEST AS CARDIAC MURMURS
- Myocardial disease
- Disruption to action potential propagation, Abnormalities in contraction
- MANIFEST AS CARDIAC DYSRHYTHMIAS
How does myocardial disease manifest?
- No clinical signs
- Poor performance (AF, VPD’s)
- Collapse (Multiple VPD’s and VT)
- V rarely death (VT to VF)
How are Cardiac Dysrrhythmias diagnosed?
- Diagnosis
- ECG
- Evaluation of underlying cause
- Blood tests, echocardiogram, other
What is Myocarditis?
Inflammation of the myocardium
Causes of myocarditis?
- Bacterial
- Staph aureus
- Strept equi
- Clostridium chauvoei
- Mycobacterium spp
- Secondary to sepsis, pericarditis, endocarditis
- Borrelia burgdorferi – (Lyme disease)
- Viral
- FMD, EIA, EVA, EIA, AHS
- Parasitic
- Lge strongyles, Toxoplasma, Sarcocystis
Techniques used for myocardial evaluation?
- Echocardiography
- Dobutamine-atropine stress echocardiography
- Can evaluate the heart at increasing heart rates
- Myocardial biopsies
- Ultrasound guided
- ECG
Which is the most important cardiac dysrhythmia in the horse?
- Atrial fibrillation
- Lack of coordinated atrial electrical activity
What can trigger atrial fibrillation?
Can be triggered by electrolyte/acid-base imbalances, anaesthetic and drug administration (that causes bradycardia), exercise
Clinical signs of atrial fibrillation?
- None
- Exercise intolerance/poor performance
- Epistaxis
- Weakness/syncope
- Myopathy
- Colic
- CHF
- Cattle - primary GI disease (also foot rot and pneumonia). Also see anorexia and decreased milk production
Diagnosis of atrial fibrillation?
- Auscultation and physical examination
- Resting ECG
- No p wave
- Normal qrs complex and t waves
- f (fibrillation) waves
- Further diagnostics PRIOR to attempting treatment
- Assessment of electrolytes and acid-base abnormalities
- Echocardiography to assess for underlying cause/chamber enlargement
- Exercising ECG
What is paroxysmal atrial fibrillation?
- lasts less than 24-48 hrs and spontaneously convert
- Sometimes associated with K+ depletion (Furosemide) and administration of bicarbonate
Treatment of atrial fibrillation?
- Pharmacological: Quinidine sulphate (Quinidine gluconate) (Negative inotrope)
- Monitor toxicity by assessing prolongation of QRS complex
- DC Cardioversion
Side effects of Quinidine sulphate (Quinidine gluconate)?
- Fatal dysrhythmias
- Colitis – drug very irritant to mucosa
- Laminitis /nasal oedema/ataxia
Prognosis of paroxsymal atrial fibrillation?
Excellent to good – unless keeps recurring
Prognosis of sustained atrial fibrillation with no underlying cardiac disease?
- < 3months – good either technique
- >3 months – better with DC conversion
- Risk of re-fibrillation – risk factors there
