Investigators will assess the impact of treatments for atrial fibrillation on participant's thrombotic status

AF affects 1 in 4 people in their lifetime. Although generally thought of as a safe heart rhythm disturbance, the risk associated with AF is through the formation of clot (thrombus) within the heart which be ejected from the heart when it contracts causing a heart attack or perhaps more devastatingly a stroke.

The mainstay of treatment for AF involves thinning the blood with drugs such as warfarin or newer drugs termed novel oral anticoagulants. In addition to this there are 3 main ways of treating the underlying rhythm disturbance:

1. Accept the irregular heart rhythm and simply control the heart rate with heart rate limiting drugs such as beta blockers or digoxin in addition to the blood thinning medicines.
2. Restore the normal heart rhythm with with an electrical shock termed a direct current cardioversion (DCCV). This is usually a temporary measure, indeed 70% of whom will have reverted to AF by 12 months.
3. Attempt to permanently restore sinus rhythm through an atrial fibrillation ablation procedure.

The investigators study, through use of a relatively novel bedside test will examine the effects of each of these management strategies on the thrombotic status of the participant's blood.

Investigators will take blood from in total 500 participants divided between each of the above management strategies which has been decided by their parent teams (i.e. study does not affect their treatment).

Investigators will draw blood from the participants on up to 5 separate occasions over a 12 month period. In the group undergoing a DCCV, blood will be drawn shortly before and after the intervention and at 3 and 12 months post intervention. In the group undergoing an AF ablation blood will be drawn on 5 occasions - the day before the procedure, 1-2 days post, 3-4 days post, 3-4 months post and 12 months post. In the group treated with standard medical therapy, blood will be drawn at the time of enrolment in the study and at 3 and 12 months post enrolment.

It is the investigators hypothesis that permanent restoration of sinus rhythm through an atrial fibrillation ablation procedure will positively affect an individual participant's thrombotic status. There has been recent publication of registry data from the United States suggesting the long term rate of stroke in the population following an AF ablation approaches that of the population who have never suffered AF.

The investigators believe that the cause of the improvement in stroke rates following ablation is an improvement in thrombotic status which we hope to be test for the first time in a powered, prospective study.

Inclusion Criteria:

1. Male and female patients aged 18 years or over
2. Patients diagnosed with atrial fibrillation managed in one of the 3 ways outlined above
3. The patient is willing and able to understand the Patient Information Sheet and provide informed consent
4. The patient must agree to comply with the drawing of blood samples for the assessments

Exclusion Criteria:

1. Male and female patients aged < 18 years of age
2. The patient has, in the opinion of the investigator, significant neurological, hepatic, renal, endocrine, gastrointestinal, pulmonary, haemorrhagic, metabolic or other disease likely to confound the study requirements or analyses
3. The patient has a history of substance abuse or demonstrates signs or clinical features of active substance abuse or psychiatric disease
4. Alcohol consumption above recommended safe levels (i.e. more than 21 units per week for males, or more than 14 units per week for females) due to the potential effects of high alcohol levels on platelet reactivity
5. Any illness deemed significant by the investigator during the four (4) weeks preceding the screening period of the study
6. Any major bleeding diathesis or blood dyscrasia (platelets < 70 x 109/l, Hb < 8 g/dl, INR > 1.4, APTT > x 2 UNL, leucocyte count < 3.5 x 109/l, neutrophil count < 1 x 109/l)
7. Currently enrolled in an investigational device or drug trial

Population of interest are adults (>18) diagnosed with atrial fibrillation (AF) who will be treated in one of 3 ways:

1. Medical management
2. Direct current cardioversion
3. AF ablation

In total we aim to sample 500 patients divided into:

100 - Medical management 100 - Direct current cardioversion 300 - AF ablation