Arrythmias Flashcards
What causes arrhythmia?
- Abnormal pacemaker/triggered activity
* Re-entry
What is AF?
Contraction of atria is uncoordinated, rapid and irregular.
This disorganised electrical activity in the atria also leads to irregular conduction of electrical impulses to the ventricles.
How does the risk of stroke increase with AF?
- Blood collects in atria and forms blood clots
- Clots can become emboli and travel to the brain and block cerebral arteries causing ischaemic stroke
How does AF present?
- Palpitations
- Chest discomfort
- SOB
- Syncope
- Symptoms of associated conditions (stoke, sepsis or thyrotoxicosis)
What does AF look like on an ECG?
- Narrow QRS complex Tachycardia
- Irregularly irregular rhythm
- Absence of P-waves
What are the causes of AF?
Mrs SMITH • S - Sepsis • M - Mitral valve pathology • Ischaemic heart disease (IHD) • T - Thyrotoxicosis • H - HTN
What is the treatment for AF?
- Rate OR rhythm control
* Anticoagulation to prevent stroke
What would you NOT give rate control treatment for AF?
- There is a reversible cause of AF
- Their AF is new onset (48hrs)
- Their AF is causing HF
- They remain symptomatic despite being effectively rate controlled
What are the drug options for rate control of AF?
- Beta blocker -> atenolol 50-100mg o.d.
Remember atenolol is not licensed in HF, but rate control is not given in AF with HF - CCB -> diltiazem
- Digoxin
What is the mechanism of action of digoxin
Reversibly inhibits Na-K ATPase, causing an increase in intracellular Na+ and Ca2+ inside the myocardial cells, increasing contractility of the heart.
ncreases vagal afferents to the heart which reduces SAN firing, decreasing the HR.
If rate control monotherapy for AF does not work, what would you do?
Combine 2 of:
- Beta blocker -> atenolol 50-100mg o.d.
- CCB -> diltiazem
- Digoxin
When would you give rhythm control for HF?
- There is a reversible cause of their AF
- Their AF of new onset (<48hrs)
- Their AF is causing HF
- They remain symptomatic despite being effectively rate controlled
Why can you not give rate control to a patient who has had AF>48 hrs?
The risk of clots forming is greater is the patient had had AF for >48hrs.
- If a normal sinus rhythm was restored through rhythm control, the clots could become dislodged and would increase the risk of embolic stroke.
What would you give for rhythm control?
Cardioversion:
- Defibrillation
- Drugs:
Flecainide
Amiodarone
Long-term
- Beta-blockers
- Dronedarone
- Amiodarone
What is the CHA2DS2-VASc score?
Assesses whether patient with AF should be started on anticoagulation. Score: • 0 = no anticoagulation • 1 = consider anticoagulation • >1 = offer anticoagulation
What does the CHA2DS2-VASc score look at?
- C - Congestive HF
- H - HTN
- A2 – Age >75 (scores 2)
- D - Diabetes
- S2 – Stroke or TIA previous (scores 2)
- V –Vascular disease
- A – Age 65-74
- S – Sex (female)
Which anticoagulants can you give for AF?
- Warfarin
- Apixaban
- Dabigatran
- Rivaroxaban
DO NOT GIVE ASPIRIN
When would you give a NOAC?
- > 75yrs
- Prior stroke or TIA
- HTN
- DM
When would you give dabigatran?
- Previous systemic embolism
- LVEF <40%
- > 65yrs + DM, CAD or HTN
How do you assess a patient’s major risk of bleeding whilst on anticoagulation?
HAS BLED
- H – HTN
- A – Abnormal renal and liver function
- S – Stroke
- B – Bleeding
- L – Labile INRs (whilst on warfarin)
- E – Elderly
- D – Drugs or alcohol
What is paroxysmal AF?
AF comes and goes in episodes, usually not lasting >48hrs.
How is paroxysmal AF treated?
“pill in the pocket” approach -> flecainide
What is the mechanism of action of amiodarone?
Class III antiarrhythmic -> Blocks the K+ rectifier currents that are responsible for repolarisation of the heart to slow down nerve activity and relax an overactive heart.
What is the mechanism of action of flecainide?
Blocks the Ca2+ channel to slow the upstroke of the cardiac action potential
What is the mechanism of action of dronedarone?
Inhibits rapid Na+ currents, antagonises alpha and beta receptors, block K+ outward current and blocks Ca2+ inward currents
What do you do if a patient’s INR >8 and they are having a major bleed?
- Stop Warfarin
- IV Vit K 5mg
- Give prothrombin complex concentrate or FFP
What do you do if a patient’s INR >8 and they are having a minor bleed?
- Stop warfarin
- IV Vit K 1-3mg
- If INR has not gotten to target level in 24 hours, give Vit K again
- Give warfarin when INR <5
What do you do if a patient’s INR >8 and they are not bleeding?
- Stop warfarin
- Oral Vit K 1-5mg
- If INR has not gotten to target level in 24 hours, give Vit K again
- Give warfarin when INR <5
What do you do if a patient’s INR is between 5-8 and they are bleeding?
- Stop warfarin
- IV Vit K 1-3mg
- Give warfarin when INR <5
What do you do if a patient’s INR is between 5-8 and they are not bleeding?
- Stop next 1/2 doses of warfarin
- Reduce subsequent maintenance dose
What is the target INR for AF and VTE?
2.5
What are the side effects of warfarin?
- Haemorrhage
- Teratogenic (safe in breastfeeding)
- Purple toes
- Skin necrosis
What may potentiate the effects of warfarin?
- Liver disease
- P450 enzyme inhibitors (ciprofloxacin, amiodarone, fluconazole)
- Cranberry juice
- NSAIDs
