Causes of and treatment for cardiac arrhythmias Flashcards
What are cardiac causes of episodic weakness / syncope?
- Compromised cardiac output
- Cardiac arrhythmia - tachy/bradyarrhythmia
What can cause compromised cardiac output?
- Congenital heart disease (esp. AS, rev. PDA)
- Dilated cardiomyopathy
- Hypertrophic cardiomyopathy (cats)
- Cardiac tamponade
- Cardiac neoplasia
What are different classes of antiarrhythmic drugs?
- Class 1 = Sodium channel blockers - lidocaine
- Class 2 = B-blockers - atenolol
- Class 3 = Potassium channel blockers - amlodipine / sotalol
- Class 4 = Calcium channel blockers - diltiazem
What can cause a supraventricular tachycardia?
- Sinus tachycardia
- Ectopic focus - irritation of the atria / junction
- Re-entry circuit
What is emergency tx of supraventricular tachycardia?
- Vagal manoeuvre - high vagus tone at AV node = gentle pressure on eyelids / massage carotid sinus on jaw
- IV Esmolol (beta-blocker)
- IV Diltiazem
- Oral diltiazem if no IV preparation
- Oral sotalol also possible
** Sodium channel blockers don’t work **
What is wolf-parkinson-white syndrome?
- Abnormal conduction between atria + ventricles, round + round inducing a tachycardia
How do you identify different tachycardias?
narrow QRS = supraventricular
Wide QRS = ventricular
* No P waves = Atrial fibrillation
* Irregularly irregular = Atrial fibrillation
*
How would you treat atrial fibrillation?
- Treat underlying cardiac disease, CHF
- Normally accept the rhythm (underlying disease with atrial stretch); do not aim to convert it.
- GOAL: Control ventricular response rate to AF
- Use drugs which slow conduction through the AVN
- Digoxin
- Ca++ channel blockers
What effects does digoxin have?
- Negative chronotrope - slows HR
- Weak positive inotrope
- Vagomimetic
How does diltiazem work?
- Ca++ channel blocker
- Slows conduction across AVN
- Negative inotrope
When would you NOT use beta blockers?
- If uncontrolled congestive heart failure / poor systolic function
What can cause vetricular ectopics?
- Underlying cardiac disease; CHF; cardiomyopathies
– Myocardial hypoxia / ischaemia etc. - Catecholamines (e.g. stress, pain etc.)
- Acidosis
- Hypokalaemia
- Abdominal disease: GDV, splenic lesions (not just splenic haemangiosarcoma), sepsis, perforated gastric ulcer, pancreatitis etc.
- Thoracic trauma (myocardial contusions)
- Drug induced (e.g. digoxin toxicity)
How would you treat ventricular tachycardia?
- Emergency IV Tx - Lidocaine, Esmolol, Amidarone
- Oral antiarrhythmics - Sotalol
What needs to be excluded if bradyarrhythmias?
- High vagal tone
- Hyperkalaemia
- Hypothyroidism
- Drug side effects
What is atrial standstill?
- Absent P waves, spikey T waves, mild prolongation of the QRS complex (Hyperkalaemia)
- WHWT: Hypoadrenocorticism (Addison’s disease)
- Also consider Urinary obstruction (e.g. FLUTD), oliguric or anuric renal failure as causes of Hyperkalaemia.
- This is a sino-ventricular rhythm (SAN drives the rhythm) (so variable R-R as with sinus arrhythmia) (internodal tracts travelling from SAN to AVN; no atrial depolarisation).
