Increase in Strokes Among Patients with Atrial Fibrillation

Analysis of American hospital data found that the incidence of strokes associated with atrial fibrillation (AF) shot up 42% in just 7 years.

Researchers from the University of Kansas Medical Center analyzed data from the Nationwide Inpatient Sample and found that the number of people with AF who were hospitalized for ischemic stroke rose from about 71,000 in 2003 to 101,000 in 2010.

“It appears that AF-associated cerebrovascular accidents (CVA) are increasing despite advances in management,” wrote the authors of the study, which was published in The Journal of the American College of Cardiology and presented live at the College’s recent annual meeting.

Moverover, the authors note, “outcomes are consistently worse in this group compared to non-AF-associated CVAs.”

The increase in total strokes stems both from an increase in the total number of Americans who suffer AF and an increase in the co-morbidities that further boost stroke risk for those who have AF.

Among all 27 million AF patients who appeared in the sample — most of whom never suffered a stroke — the percentage who scored higher than 2 on the CHADS2 scale (Congestive heart failure, Hypertension, Age > 75 years, Diabetes, and prior Stroke or TIA or thromboembolism) rose by nearly half, from 20% in 2003 to 29% in 2010.

That dramatic rise in total CHADS2 scores reflected the combined effect of significant increases in each of the scale’s individual components.

The incidence of heart failure among all hospital patients with AF rose from 31% in 2003 to 37% in 2010. The incidence of hypertension rose from 45% to 48%. And the incidence of diabetes rose 24% to 29%.

The incidence of prior stroke rose the most sharply of all, from just 5% in 2003 to 12% in 2010.

Part of the reason the stroke component of the CHADS2 scale worsened so dramatically was that hospitals have gotten better at treating AF patients who suffer strokes.

Their mortality rate fell during the course of the study from 12% to 9%. That said, such patients still die more frequently than stroke victims with no AF, whose mortality rate fell from 5.1% to 4.1%.

Increasing patient ages also contributed to the increase in stroke rates among patients with AF. In 2003, 37% of the hospitalized stroke patients who also had AF were 85 or older. By 2010, older patients were 42% of the total pool.

Such changes in demographics and comorbidities explain the vast majority of the increase in strokes among patients with AF, but stroke figures actually rose more than all such adjustments would predict, leaving the researchers looking for additional causes.

Overall, of the more than 3 million strokes evaluated, 22% were related to AF, and that percentage rose slightly over the course of the study, from 21.2% to 22.5%.

But those percentages varied greatly with patient demographics. Some 25.2% of white stroke patients also had AF but just 11.4% of black stroke patients did.

Gender mattered as well. Just over 24% of all women hospitalized for stroke had AF. Among men, however, the figure was 18.7%.