Strike out stroke

Even if you aren't technically in the high-risk category for stroke - having high-blood pressure or being overweight, for example - the risk of stroke is still present. Especially stroke caused by an irregular heartbeat.

Atrial fibrillation (AF), an irregular heartbeat, is the commonest heart rhythm problem in cardiological clinical practice, says associate professor Tan Ru San, senior consultant, Department of Cardiology, and director of Clinical Trials, at the National Heart Centre.

The abnormal beat of the upper chambers of the heart can cause stagnation of blood in the left upper chamber, where clots can form and be carried in the bloodstream to the brain. This leads to a large area of brain damage and can lead to permanent disability and death.

"And the problem with an AF-induced stroke is that they can be recurrent," he says.

Atrial fibrillation occurs in 1 per cent of the population, and is the cause for one in five stroke incidents. In octogenarians, the prevalence of AF is 15 per cent. Other conditions associated with AF are congestive heart failure, diabetes, high blood pressure, valve disease, coronary artery disease and especially prior stroke.

Problem is, AF is largely asymptomatic. "Some people have heart palpitations, shortness of breath and tiredness, but some don't feel anything at all," says Prof Tan.

While it's not the main cause of stroke, he says, it causes more severe disability in stroke, with a higher risk of death. Women are at higher risk of developing AF compared to men, and they also have a higher risk of AF-related stroke.

The solution to prevent AF-related stroke is to take anticoagulation drugs to prevent blood clots. "If people with AF take the appropriate blood-thinning agents, this can reduce stroke risk by 60 per cent," says Prof Tan, adding that the risk of bleeding from the anti-blood coagulant is acceptable.

However, it's not as straightforward as that. Prof Tan notes that for patients who do know they have AF, if they don't have at least one of the risk factors, such as advanced age, hypertension, diabetes, prior history of stroke, and presence of heart failure, anticoagulation is not recommended because any potential stroke risk reduction is outweighed by the bleeding risk associated with anti-thrombotic treatment.

Also, those with AF have been reluctant to take blood thinners, such as Warfarin, because of the side effects and risks.

New drugs

Now, new drugs like Rivaroxaban (brand name Xarelto) could well change the scenario, says Professor Christoph Bode, chairman, Department of Internal Medicine III of the University of Freiburg, Germany.

Patients are reluctant to go on Warfarin because dosages need to be individualised, constant monitoring is needed, and there is a risk of bleeding in the brain.

Rivaroxaban has been proven to be easier to use and more effective than Warfarin, and it's a scientific breakthrough, says Prof Bode, who was involved in the development of the drug.

Rivaroxaban is a single fixed dosage and doesn't require monitoring because it has a different mechanism, he explains. Warfarin is a Vitamin K inhibitor that inhibits four blood-clotting proteins, while Rivaroxaban is a factor Xa inhibitor that inhibits only one blood-clotting protein.

"Rivaroxaban has the potential to become a gold standard blood-thinning agent," he says, adding that it just got tested in one of the most robust clinical trials using double-blind and double-dummy methodology in the prevention of AF-related strokes.

In Germany, about 45 per cent of the elderly with AF are not put on blood thinners for fear of bleeding. But with a drug like Rivaroxaban, the risk of fatal bleeding is cut by half and the risk of intracranial bleeding is cut by 35 per cent. It can also do 20 per cent better than Warfarin in reducing stroke and systemic embolism.

The biggest problem to preventing AF-related stroke, however, is detecting AF itself. "When a person has the symptoms then an ECG (electrocardiogram) can detect AF. But in many patients, there are no symptoms so they don't get diagnosed," explains Prof Bode.

Prof Tan also points out that there is temporary and transient AF - which means it can come and go, but still carry the same stroke risk for the patient. "Not all irregular heartbeats are due to AF either," he adds.

But doctors would only prescribe a blood thinner if an ECG confirms an irregular heartbeat. And it isn't the norm now for folks to take ECGs on a regular basis just to detect AF.

"The problem is that AF is a tricky disease, while it also has a high stroke risk," says Prof Bode. But with a drug now that is effective, safe and convenient to take, at least there is a means to substantially reduce the dangers associated with AF.