Nonvalvular Atrial Fibrillation and Risk of Stroke

Rajat Deo, MD, assistant professor of medicine at the University of Pennsylvania

Atrial fibrillation is a common arrhythmia. It affects the atria, and it increases the risk of thromboembolic events—in particular, ischemic stroke and systemic embolization.

In patients with atrial fibrillation, it is important to assess their risk of stroke or systemic embolization. As of 2014, the American College of Cardiology and the American Heart Association guidelines recommend the use of the CHA₂DS₂ VASc scoring to assess overall stroke and systemic embolization risk. Among patients with atrial fibrillation who have a CHA₂DS₂ VASc score greater than or equal to 2, I do use it. I provide anticoagulation for those individuals.

The GLORIA-AF Registry is an international registry of over 15,000 patients. In phase II of the study, the investigators were interested in understanding the baseline characteristics of atrial fibrillation and anticoagulation use in the current era—in the era of novel oral anticoagulants. These investigators have recently demonstrated that, compared to a time when novel oral anticoagulation use was not available, there has been a significant increase in anticoagulation. In particular, these investigators have noted, in the United States as well as Europe, an increase in the use of NOAC (novel anticoagulant) therapies. In addition, these investigators have also noted that there are about 10% to 20% of individuals across the world that do not receive adequate anticoagulation for stroke prevention in nonvalvular atrial fibrillation.

The GLORIA AF Registry is only one of many international registries for understanding anticoagulation use in individuals with atrial fibrillation. Again, this phase 2 study included only about 15,000 patients. We now recognize that we have available very large international registries of hundreds of thousands of patients. The American College of Cardiology has its own registry of atrial fibrillation patients, and we recognize that the 80% to 20% anticoagulation undertreatment rate reported in GLORIA is, in my opinion, quite optimistic. My own opinion on this is that based on various data, it appears that the anticoagulation undertreatment rate is much higher than that (on the order of about probably 40% to 50%.

More importantly, these investigators have demonstrated that there is a significant proportion of individuals who are prescribed NOAC therapies. In fact, the majority of anticoagulation prescriptions in this registry suggest the use of NOAC therapies. I don’t believe that is the case across the world right now. I think, again, these findings are quite optimistic from the standpoint of NOAC use and NOAC availability.

I think the final issue, here, that is important to recognize is that this study (the way it’s designed) is to look at an initial prescription. However, we recognize that in the field of atrial fibrillation and anticoagulation, and especially with NOAC therapies, that adherence is also a major issue. So, it’s not just about the initial prescription, it’s also about adherence. I think we need to have a better understanding on the continuation of any of these therapies in the atrial fibrillation population.