Does AF cause stroke?

There’s no doubt that atrial fibrillation is associated with an increased risk of stroke, but is it a direct cause or rather the company it keeps?

This is the tricky question Associate Professor Andrew McGavigan was tasked with answering during a session on controversies in stroke prevention in atrial fibrillation.

He told delegates here at CSANZ2016 that the question was hard to answer definitively because the data was conflicting.

It was also challenging to interpret because of differences in patient populations and endpoints, differences in anticoagulation and insufficient stroke events.

In theory, if AF caused thromboembolic-stroke there should be a relationship between the timing of AF episodes and stroke events.

Conversely, if AF itself did not cause thrombo-embolic stroke then no relationship should exist between the timing of AF episodes and stroke events.

There should also be no relationship between AF burden and stroke risk, said Professor McGavigan who is an electrophysiologist at the Flinders Cardiac Clinic in South Australia.

“There is no clear-cut temporal relationship… we need more collective registry investigations,” he said.

Why does it matter?

 The answer to the question wasn’t just a ‘nice to have’, it actually had direct clinical implications, Dr McGavigan told delegates.

 The answer had implications for a high burden of AF in patients with a low CHADS-VASC scores and a low burden of AF in patients with a CHADS/VASC score of 1.

It also had implications for the role of rhythm control strategies in reducing stroke risk and in decision-making regarding oral anticoagulation post AF ablation.

“Clearly more data is needed on improved long-term AF recording investigations – the more you look the more you find,” he said.

“I would also like to see epidemiological data looking at stroke risk in paroxysmal AF and non- paroxysmal AF across the CHADS-VASC spectrum.”

He also suggested the CHADS-VASC might need to be revised to include AF duration and type.

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