Tachycardia: Atrial Fibrillation

Atrial Fibrillation

• Rapid and uncoordinated electrical activity within the atria
• ECG: absence of P waves and irregular ventricular response
• Occurs in 10% of patients of patients over 80 years
• Associated with blood stasis in Left atrium, with clot formation and embolic event

Paroxysmal AF
- Self terminating AF
Persistent AF- Rhythm sustained for longer than 7 days
Permanent AF
- Continues AF and cardioversion has failed or it is no longer attempted
Lone AF
- AF occurring in the absence of structural heart disease in pt younger than 60 years

Associated with heart failure, hyperthyroidism, hypertension, WPW syndrome, cardiac surgery, myocardial infarction, myocarditis, pericarditis, acute pulmonary disease, mitral valve disease

Management:
- 12 lead ECG to capture rhythm and rate
- Blood tests: FBC, U+E, LFTs, TFTs
- Echocardiogram
- If no heamodynamic compromise anticoagulation and cardiovert within 3 weeks, and continue anticoagulation 4 weeks post cardioversion (goal INR 2.0-3.0)
- Use beta blockers. calcium channel blockers or digoxin to maintain R 60-100
- Emergency Cardioversion is indicated in those with hypertension, angina, heart failure or decreasing conscious level due to poor output.

Anticoagulation in AF

RISK factors for anticoagulation: Mitral stenosis, previous VTE, HF, systolic dysfunction, diabetes, HTN, mechanical heart valve and older age.

Chads2 score is used in patients without valvular disease to determine need and type of anticoagulation: - Low and intermediate risk can be treated with Aspirin alone.
- Those who are not candidates for warfarin can use CLOPIDOGREL and Aspirin but bleeding risk is higher and ti is inferior for preventing ischaemic CVA when compared to warfarin.
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Newer Agents:
- Dagibatran

• Direct Thrombin inhibitor
• RE-LY trial showed Dagibatran to be superior to warfarin in preventing ischameic and haemorrhagic CVA, with reduced risk of life threatening bleeding but higher risk of GI bleeding.
• No lab monitoring required but no test can measure extent of anticoagulation
• No reversal agent available 

- Rivaroxaban / Apixaban

• Oral Factor Xa inhibitor
• Non inferior to warfarin for stroke prevention and demonstrates reduced risk of intracranial bleeding
• Risk of thrombotic event increased in first 28 days after it is stopped to bridging anticoagulation should be used

Non pharmacologic strategies:

• AF ablation - entails electrical isolation of the pulmonary veins so premature serial contractions can be stopped. Warfarin should be continued for 2-3 months post procedure, then CHADS2 score used to determine LT anticoagulation. 84% success rate. Complications include stroke, atrial oesophageal fistula, pulmonary vein stenosis, cardiac tamponade and death in 4.5% of patients.
• AV nodal Ablation
• Maze surgery - open cardiac surgery involving incisions and ablations of the right and left atria