CS: Problem arrhythmia Flashcards
Name 3 features of a physiological aortic flow murmu
heard during systole
noticed at rest on left heart base
quiet
What is the top diagnostic test for arrhythmia investigation?
ECG
What do you want to rule out with arrhythmias?
any underlying metabolic abnormalities (e.g. liver metabolism, low Ca, high K)
Why perform blood work on a horse with an arrhythmia?
to determine any unlying metabolic issue s- electrolyte imbalances, hypoxia, other metabolic abnormalities
What is the first sign of cardiac compensation?
tachycardia
List ECG signs of AF
F waves
normal QRS
no P waves
RR variable
What is the main treatment option for AF?
Quinidine sulphate
Other than quinidine sulphate, name 2 tx options for AF.
ANTI-ARRHYTHMIC DRUGS (as for small animals but high dose needed and can cost a lot, rarely used)
BIPHASIC ELECTRICAL CARDIOVERSION - only 2 centres in Europe offer this treatment
What dose of quinidine sulphate should be given?
10g/450kg of horse
Side effects - quinidine sulphate
CARDIOVASCULAR - tachycardia (atrial tachycardia), QRS widening, hypotension
GIT - diarrhoea, colic
Where does ventricular tachycardia (VT) originate?
this rhythm originates in the ventricles
Long-term prognosis - AF treated with quinidine sulphate
Conversion to sinus rhythm, no other heart disease- GOOD
If CHF occurs - POOR
Diagnosis <3 months = do better than older cases of AF.
When can full training be resumed in horses treated with quinidine sulphate for AF?
7-10 days after treatment
How should you treat a horse with CHF AND AF?
NOT with quinidine sulphate. Treat for CHF with positive inotropic agents, diuretics and other medications needed for stabilisation.
How does quindine sulphate work?
class 1 anti-arrhythmic - vagolytic action
increases the fibrillation threshold of atrial myocardium
ALPHA-ADRENERGIC ANTAGONIST - decreases vascular tone and MAP.
Negative inotrope
Positive chronotrope (can lead to supraventricular tachycardia).
Why does quinidine sulphate have to be given via a nasogastric tube?
cases significant oral ulceration. (IV forms also availabe)
How does Digoxin work?
Negative chronotrope
Positive inotrope
Decreases AVN conduction and ventricular response rate.
Increased vagal tone
What happens to plasma levels of digoxin when concurrently administered with quinidine sulphate?
Plasma levels increase because of competitive protein binding between the 2 drugs.
What should you do before initiating quinidine sulphate treatment?
place an IV catheter in case rapid venous access is required for treatiing severe arrhythmia or hypotension.
What do crackles in the CdV lung fields suggest?
pulmonary oedema - suggestive of left sided HF.
What is the top differential for a large dog with biventricular compensated HF?
Cardiomyopathy due to DCM
What can you measure using echocardiography? 4
- contractility
- FS%
- diameter of chambers
- wall thickness (free and septal walls)
What do increased left atrial to aortic ration, enlarged LV diameter and reduced FS% suggest?
global mycoardial dysfunction
Outline evidence-based treatment for HF - 4
- Furosemide (diuretic to reduce circulating load)
- Pimobendan (calcium sensitiser increases cardiac contractility)
- ACEI (Benazepril) - blocks Ang2 to relieve hypertension
- Digoxin (anti-arrhythmic and positve inotrope)
What should you treat AF with if there is presence of underlying heart failure ?
Digoxin first
What should you treat AF with if there is NOT presence of underlying heart failure ?
beta-blocker first (this area is less well researched)
What is Holter monitoring?
allows continuous ECG for 24-48 hours. 2 electrodes are contained in a vest worn by the dog on either side of the thorax.
Prognosis - DCM with acute onset CHF
very guarded
What are dobermans prone to?
sudden death due to arrhythmias
Are CHF maladapted hearts predisposed to AF?
Yes - therefore if it is converted to normal sinus rhythm, it is likely to revert.
Will NTproBNP levels be altered in AF?
No but they will be altered in DCM and MVD.
Name drugs that can be used for pharmacological conversion of AF to normal sinus rhythm
Amiodarone
Sotalol
If a dog has no signs of cardiac disease is electrical or pharmacological cardioversion preferred?
Electrical conversion is preferrable.
What is atenolol?
Beta-blocker to lower HR
What type of dogs is relapse to AF most common?
giant breed dogs.
