Time to recalibrate? Stroke risk may be lower than reported

Stroke risks after an atrial fibrillation (AF) diagnosis may be lower than previously thought. The finding, published Jan. 27 in the Journal of the American College of Cardiology, has prompted a call to reassess oral anticoagulation (OAC) among these patients.

“The risk of ischemic stroke among patients with AF and a CHA2DS2-VASc score of 1 seems to be lower than previous studies have indicated. This earlier finding may have led to unnecessary, and potentially harmful, OAC treatment of low-risk patients,” wrote Leif Friberg, MD, PhD, from the Karolinska Institutet at Danderyd Hospital in Stockholm, and colleagues. Friberg et al collected and cross-matched patient data from several Swedish health registries for this analysis.

Using a broad stroke diagnosis and including ischemic stroke, unspecified stroke, transient ischemic attack (TIA) and pulmonary embolism, they found a 44 percent higher risk than using ischemic stroke alone. However, they found that this increase also was predicated on the number of stroke events occurring within the first four weeks of index hospitalization for AF.

When using a quarantine method to assess long-term implications of the score of 1, annual stroke rates changed. By removing the first four weeks from consideration of risk, stroke rates dropped significantly from previously reported rates of more than 2 percent. Women, whose only point on the scale was sex, had an annual ischemic stroke rate of 0.1 to 0.2 percent. Men with a 1 point score had an ischemic stroke rate of 0.5 to 0.7 percent, rising to 1.3 percent if TIA, pulmonary or arterial embolism and unspecified stroke were included. Friberg et al argued against using TIA as an outcome as they found the diagnosis “difficult to validate.”

They wrote that when patients have a CHA2DS2-VASc score of 1, “No benefit is anticipated for routine administration of OAC agents to these patients.”