Arrhythmias - Atrial Fibrillation Flashcards
What is Atrial Fibrillation?
Unco-ordinated, rapid and irregular contraction of the atria.
Pathophysiology of Atrial Fibrillation.
Disorganised electrical activity that overrides the normal, organised activity from the Sinoatrial node.
Effect of Atrial Fibrillation of Ventricles (4).
Irregular Conduction of Electrical Impulses to Ventricles :
1. Irregularly irregular ventricular contractions.
2. Tachycardia.
3. Heart Failure (poor filling during diastole).
4. Risk of ischaemic-embolic stroke.
Aetiology of Atrial Fibrillation (5).
SMITH :
1. S - Sepsis.
2. M - Mitral Valve Disease (Rheumatic HD).
3. I - Ischaemic Heart Disease.
4. T - Thyrotoxicosis.
5. H - Hypertension.
What is Valvular AF?
Patients with AF also have moderate or severe mitral stenosis or a mechanical heart valve. Other/Absent valve disease is non-valvular AF.
Differential Diagnoses of Irregularly Irregular Pulse (2).
- Atrial Fibrillation.
- Ventricular Ectopic.
* Use ECG to differentiate and Ectopics disappear when HR gets over certain threshold (e.g. exercise).
Clinical Presentation of Atrial Fibrillation (6).
- Asymptomatic & Incidental Findings.
- Palpitations.
- SOB.
- Syncope.
- Symptoms of Associated Conditions e.g. Stroke, Sepsis, Thyrotoxicosis.
- Irregularly Irregular Pulse.
ECG Findings in Atrial Fibrillation (3).
- Absence of P Waves (lack of co-ordinated atrial electrical activity).
- Narrow QRS Complex Tachycardia.
- Irregularly Irregular Ventricular Rhythm.
Management of Atrial Fibrillation (2).
2 Principles :
1. Rate/Rhythm Control.
2. Anticoagulation (Prevention of Stroke).
What is the rationale of Rate Control? (3)
- Atria pump blood into the ventricles but since atrial contractions are unco-ordinated, ventricles fill up by suction and gravity.
- A higher HR means less time is available for filling which reduces CO.
- By getting HR below 100, diastolic time is increased so ventricles fill with more blood.
Contraindications of Rate Control (4).
- Reversible Cause.
- New-Onset (Last 48 Hours).
- Co-Existent Heart Failure.
- Symptomatic Despite Effective Rate Control.
Options for Rate Control (3).
- B-Blocker 1st Line.
- Non-DHP CCB e.g. Dilitazem, Verapamil (not preferable in HF),
3*. Digoxin (sedentary people, needs monitoring due to risk of toxicity).
* Monotherapy or Dual Combination Therapy.
What is the principle of rhythm control?
Return patient to normal sinus rhythm - single ‘cardioversion’ event or long-term medical rhythm control.
Timings of Cardioversion (2).
- Immediate - Onset < 48 hours or haemodynamically unstable = HEPARINISE patient.
- Delayed - Onset > 48 hours and stable.
Methods of Cardioversion (2).
- Pharmacological - 1st line Flecanide (or Amiodarone if structural heart disease).
- Electrical (sedation/GA and cardiac defibrillator to rapidly shock the heart back into sinus rhythm).
Important Considerations of Delayed Cardioversion (6).
- ANTICOAGULATION 3 weeks prior to Cardioversion (clot may have formed in 48 hours).
- RATE CONTROL whilst waiting for Cardioversion.
- Alternative : TOE to exclude left atrial appendage (LAA) Thrombus) = Heparinise and Cardiovert immediately.
- Electrical > Pharmacological.
- Anticoagulation for at least 4 weeks after.
- If high-risk of failure e.g. recurrent, previous failure 4 weeks Amiodarone/Sotalol prior.
Methods of Long-Term Medical Rhythm Control (3).
- B-Blockers (1st line).
- Dronedarone (2nd line + successful cardioversion).
- Amiodarone (HF or left ventricular dysfunction).
What is the main issue with cardioversion?
The moment a patient switches from AF to sinus rhythm presents the highest risk for embolism (stroke).
How is the shock synchronised in electrical cardioversion?
Sync to R wave to prevent delivery of a shock during the vulnerable period of cardiac repolarisation (which may induce VF).
What scoring system is used to assess whether a patient should be started on anticoagulation if they have AF?
CHA2DS2-VASC Score :
1. C - Congestive HF.
2. H - HTN.
3. A - Age > 75 (2).
4. D - Diabetes.
5. S - Stroke/TIA (2).
6. V - Vascular Disease.
7. A - Age (64-75).
8. S - Female Sex.
* 0 = No Anticoagulation; 1 = Consider in Males; 2+ = Offer.
Methods of Anticoagulation (2).
- Warfarin.
- NOACs.
What investigation is still advised if CHA2DS2VASC score is 0/1?
TOE to exclude valvular heart disease.
What scoring system is used to assess a patient’s risk of major bleeding whilst on anticoagulation?
ORBIT Tool :
1. Low Haemoglobin(<130 males or <120 females) /Haemoatocrit (<40% in males or <36% in females) = 2 Points.
2. Age 75+ = 1 Point.
3. Previous Bleeding (GI, Intracranial) = 2 Points.
4. Renal Function (GFR < 60) = 1 Point.
5. Antiplatelet Medications = 1 Point.
* 0-2 : Low; 3 : Medium; 4-7 : High.
What scoring system was previously used instead of ORBIT?
HASBLED :
1. H - HTN.
2. A - Abnormal Renal/Liver Function.
3. S - Stroke.
4. B - Bleeding.
5. L - Labile INR (Warfarin).
6. E - Elderly.
7. D - Drugs/Alcohol.
