Thrombosis Australia presented a webinar with Dr Peter Purnell (cardiovascular imaging specialist based in Western Australia), and Professor Vincent Thijs (Stroke neurologist and clinician researcher Austin Health in Victoria) to discuss relevant information and current research related to Atrial fibrillation (AF).

Below is a summary of a few topics covered during the webinar.

Dr Purnell also acted as moderator for this session and commenced the conversation with some background information:

• atrial fibrillation is the most common cardiac arrythmia seen in adults
• 1% incidence worldwide; higher prevalence among those aged over 75 years at 9%
• electrical problem often associated with mechanical issues of the heart
• changes in the electrical conduction causing motor problems which cause stasis, slow flow, and increased risk of clots, which if break off from the heart and can cause embolism
• anticoagulation has been recognised as a treatment for a long time as it is effective

Dr Purnell:

• Australian researchers have demonstrated on trans-oesophageal echo the electromechanical remodeling and we can measure the reduction in flow that we see in the left atrial appendage where most of the clots form
• Unfortunately, transthoracic echocardiography largely cannot see the left atrial appendage
• What has been found there is decreased blood flow in AF but it may not be as much as you would think when compared to what the blood flow is in sinus rhythm.
• The information which has emerged is the change from AF back to sinus rhythm, the reversion time you get electrical restoration, achieving sinus rhythm but you get mechanical stunning for a variable period and the left atrial appendage emptying goes to a much slower flow state and that’s where clots often form.

A question often asked is why paroxysmal AF has similar risks to chronic AF:

• that point at which blood flow returns to sinus rhythm is the highest risk period
• anyone who’s not a very acute cardioversion must be anticoagulated because it’s not the clot that may have formed but the clot which forms when the patient returns to sinus rhythm

Professor Thijs discussed the anticoagulant choices we have with AF:

The common anticoagulants used in Australia are dabigatran, apixaban, rivaroxaban, with edoxaban being used overseas. The differences between these drugs from Prof. Thijs perspective are their mechanism, the Factor Xa inhibitors versus thrombin inhibitors, dosing regimens.

They are highly effective medications compared to Warfarin. In Stroke, Prof. Thijs has tested these drugs in the context of unexplained Stroke in two large trials (Respect Esus trial tested dabigatran compared to aspirin and found no difference at the primary endpoint; Navigate Esus Trial tested found rivaroxaban was not superior to aspirin). An important point is to diagnose AF before we use these drugs and sometimes that can be difficult.

It is important to realise there is a primary and secondary prevention indication. Primary prevention would be for people at high risk of Stroke. Patients of Prof. Thijs are among the secondary prevention group – people with Transient Ischaemic Stroke associated with AF and these drugs are highly effective compared to Warfarin.

Question for Prof. Thijs – which patients would you not anticoagulate?

There are patients which have some AF symptoms however have a CHADSVASC Score of zero and therefore are very low risk.

CHADSVASC Score of one, then you need to have a discussion whether to anticoagulate.

CHADSVASC Score of two or above, anticoagulation is warranted.

CHADSVASC – acronym of risk factors for stroke in AF patients – congestive heart failure, high BP, age, sex, Diabetes, vascular disease, previous stroke or clot.

Exceptions in Prof. Thijs’s field include brain bleeding, difficult to manage situations where bleeding risk is excessive.

There is a debate about what treatment to offer

• for intracranial haemorrhage it is a difficult discussion; patients are usually eldering, frail, and with multiple cardiovascular risk factors; observational studies have shown a benefit in restarting anticoagulation
• however, the small, randomised trials do not show superiority of anticoagulation because the bleeding risk is quite high
• an alternative new option is sealing off the left atrial appendage – a trial last year where they surgically removed the left atrial appendage showed very promising results for Stroke prevention
• the left atrial appendage appears to be the main culprit with most of the Strokes that occur with AF
• perhaps mechanical closure may become a more viable option in certain circumstance; however, I think those are exceptional patients. Most patients with respond to anticoagulation.

Dr Purnell added to the conversation: The guidelines are evolving in this area and in contrast to the direct oral anticoagulant (DOAC) trials with large numbers of participants, there is not a lot of data in the left atrial appendage occlusion sphere – small trials, anecdotal data, non-randomised data – a gap which needs to be filled.

Further topics discussed:

• Valvular atrial fibrillation and DOACs
• Compliant patients on anticoagulation presents with an Ischaemic Stroke
• Patient presents with Ischaemic Stroke and AF as the presumed aetiology – what do with anticoagulation with an acute stroke?
• Paroxysmal and Chronic AF – risk factors – duration of AF and the thrombotic risk
• Implanted loop recorders to monitor AF (including published work by Prof. Thijs)

Questions asked:

• What happens when you have a myocardial infarction or acute coronary syndrome when fully anticoagulated?
• Some research suggests genetic factors which lead to differences in blood rheology and leukocyte activation – from a clinical perspective would you consider these factors in your treatment regimen?
• Are there any individuals, situations, or types of AF (paroxysmal, persistent, long-term persistent, and permanent) which places more risk of developing thrombosis?
• Is there an association of OAC type with the risk of Dementia among patients with AF?
• Should hypertrophic cardiomyopathy patients get a novel oral anticoagulant in sinus or AF?

To watch the webinar in its entirety, please click this link