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Cryptogenic Stroke and Atrial Fibrillation - The challenge of making a diagnosis

Tuesday 11 September 2018

Cryptogenic Stroke and Atrial Fibrillation - The challenge of making a diagnosis

September 17 - 23 is Atrial Fibrillation Awareness week 2018. In this article, Dr Robert Perel (Cardiac Electrophysiologist, Queensland Cardiovascular Group) talks about the challenges of cryptogenic stroke and the role of the implantable cardiac monitor in stroke management.

Stroke is one of the leading causes of disability and death for Australians[i] - every nine minutes someone in Australia will experience a stroke[ii]. Most strokes are caused by ischaemic events, occurring because of an obstruction within a blood vessel supplying blood to the brain. In some cases, despite testing during the hospital stay, the cause of a stroke remains unclear and is known as “cryptogenic” stroke or “embolic stroke of unknown source” (ESUS). It’s estimated that 25-30% of ischaemic strokes are unexplained[iii].

Atrial fibrillation (AF), a common cardiac condition whereby the heart beat becomes irregular, is believed to be responsible for a significant portion of cryptogenic strokes. About 100,000 Australians are estimated to be living with undiagnosed AF[iv].

AF can be asymptomatic and it often occurs very intermittently, so it may not be detected by conventional short-term monitoring techniques such as the 12-lead electrocardiogram (ECG), in-patient heart rhythm monitors or outpatient ambulatory 24 hour cardiac monitors such as Holter monitors.

External ECG monitoring devices mostly only enable detection of abnormal rhythms for 24 hours or when worn for specific time periods – usually 30 days or less.  However, research presented at the 2016 American Academy of Neurology Annual Meeting showed that in a real-world population of cryptogenic stroke patients, 72% of AF patients would have gone undiagnosed if cardiac monitoring had been limited to 30 days[v].

Failure to recognise and treat AF can lead to stroke. People who have AF are five times more likely to suffer from a stroke than people who do not have AF[vi].  AF-related stroke patients tend to have longer hospital stays, more severe disability and higher death rates[vii] compared with other ischaemic stroke subgroup patients.   The initiation of anticoagulation is proven to reduce the risk of AF-related stroke by two thirds.  Therefore, AF detection and treatment are vital to the management of cryptogenic stroke patients.

The 2018 National Heart Foundation of Australia (NHFA) and Cardiac Society of Australia and New Zealand (CSANZ) Atrial Fibrillation Guidelines strongly recommend longer term ECG monitoring and note that a substantial proportion of AF occurs beyond the first 30 days following a strokeviii.  Implanted cardiac monitors provide constant ECG monitoring for up to 3 years and will detect more far AF than 30 day external cardiac monitors.

The 2017 Stroke Foundation Clinical Guidelines for Stroke Management[viii][ix] also recognise the importance and need of longer term ECG monitoring for patients with embolic stroke of uncertain source.

Recent updates to the Medical Benefits Schedule (MBS) now support implanted cardiac monitor insertion for long-term continuous cardiac monitoring for the detection of atrial fibrillation in unexplained stroke and facilitate the adoption of 2018 NHFA/CSANZ and 2016 Stroke Foundation Guidelines.

Dr Robert Perel is a Cardiologist, Heart Rhythm and Cardiac Device Specialist at Mater Hospitals.  Dr Perel performs insertion of implantable cardiac monitors as part of his usual procedural work at the Mater Hospitals.  He is happy to accept referrals for insertion of this device to patients who have suffered cryptogenic stroke / embolic stroke of unknown source.

 


[i] Australian Institute of Health and Welfare 2018. Australia’s Health 2018

[iii] Liao J, Khalid Z, Scallan C, Morillo C, O’Donnell M. Noninvasive cardiac monitoring for detecting paroxysmal atrial fibrillation or flutter after acute ischemic stroke: a systematic review. Stroke 2007;38:2935–2940.

[iv] Deloitte Access Economics Pty Ltd. Off beat: Atrial fibrillation and the cost of preventable strokes. September 2011; 10-15

[v] Rogers J, Nichols A, Richards M, et al. Incidence of Atrial Fibrillation Within One Year of Cryptogenic Stroke Among a Large, Real-World Population with Insertable Cardiac Monitors. Abstract presented at: American Academy of Neurology’s Annual Meeting; 2016 April 16-20; Vancouver, BC, Canada.

[vi] Hart RG, Halperin JL. Atrial fibrillation and thromboembolism: a decade of progress in stroke prevention. Ann Intern Med. 1999

[vii] Lin HJ, Kelly-Hayes M, Beiser AS, et al. Stroke Severity in Atrial Fibrillation: The Framingham Study. Stroke. 1996; 27: 1760-1764.

[viii] National Heart Foundation of Australia and the Cardiac Society of Australia and New Zealand: Australian Clinical Guidelines for the Diagnosis and Management of Atrial Fibrillation 2018.  Heart, Lung and Circulation (2018) 27, 1209–1266

[ix] https://informme.org.au/Guidelines/Clinical-Guidelines-for-Stroke-Management-2017

Image reference: LINQ Implantable device, Image supplied and reproduced with permission from Medtronic.

 

                                  

 

 

 

 

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