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Atrial fibrillation (AF) is the most common type of heart arrhythmia, affecting about 200,000 Canadians, according to the Heart and Stroke Foundation of Canada. Caused by electrical signal disturbances in the heart, AF increases a person’s risk of stroke by three to five times. It’s estimated that 25 per cent of all strokes after age 40 are caused by AF. 

Patients with AF are more prone to developing blood clots in their upper chambers of their heart due to their irregular heart rhythm, so doctors often prescribe blood thinners to these individuals to prevent stroke. However, some individuals can’t be on blood thinners because of an unacceptably high risk of bleeding. 

In recent years, physicians have offered an alternative way to decrease the risk of stroke for these patients. A catheter is used to deploy a device to block the left atrial appendage, a pouch-like structure in the left atrium of the heart, where blood clots can form. 

According to Dr. Derek Chew, MD, a clinician-researcher at the Cumming School of Medicine (CSM), it can be difficult for physicians to know which therapy will offer the best balance of risk and benefit for patients. It’s a problem he recently tackled alongside colleagues from Duke University. 

The team simulated a virtual clinical trial of stroke prevention strategies in a group of elderly AF patients without prior stroke. The trial was created using advanced analytics to understand the risk-benefit trade-off when choosing between the two treatment options. 

Researchers found the decision is quite individual and based on the personal risk for any given patient. 

“When you apply data from large clinical trials to individual patients, there is a gap because everyone is so different,” says Chew, an assistant professor in the departments of Cardiac Sciences, Medicine and Community Health Sciences. “We wondered if we could create a matrix to show the relative benefit of each treatment option for any given patient.” 

The , published in Annals of Internal Medicine, reveals the device is a potential alternative to blood thinners in selected patients. Compared to anticoagulants, the devices decrease major bleeding risk, but concerns remain over how effective it is in preventing strokes. 

Chew, the lead author, says the study clearly shows that each patient should be assessed individually based on their own unique risk factors, adding the decision-making model may be helpful in making the decision. 

Dr. Stephen Wilton, MD, a clinician-researcher at the CSM who specializes in disturbances of the heart, agrees. 

He says physicians use clinical tests and patient information to determine which treatment option is best. Care providers must carefully consider the risks of stroke and bleeding, which can occur for a variety of reasons, such as problems with an individual’s clotting system or fragile blood vessels. 

“Individualized decision-making is very important,” says Wilton. “In addition to considering an individual patient’s risk of stroke and bleeding, there are technical issues as well. The decision is often made in consultation with other health-care teams, such as neurology.” 

Although further work is needed in this area, the research team’s model may help shared decision-making when selecting patients for left atrial appendage occlusion devices. In Calgary, insertion of these devices is reserved for highly selected patients at a high risk for both bleeding and stroke.