Vitamin K antagonists provide benefit in elderly patients with afib, study finds

Patients older than age 75 who have atrial fibrillation benefited from vitamin K antagonist therapy, although their risks for stroke and bleeding were higher than in younger patients, a recent study found.

Researchers examined a real-world cohort of hospitalized patients with atrial fibrillation from the Loire Valley AF Project in France and evaluated risk factors for stroke, thromboembolism, death, or major bleeding in those older than age 75 years, as well as the effect of vitamin K antagonist therapy on these end points. Patients younger than age 75 served as the reference group. The study results were published online Nov. 25 by Stroke.

A total of 4,130 patients age 75 or older and 4,832 patients younger than age 75 were included in the study. In the former group, 1,592 patients were age 75 to 80, 1,333 were age 80 to 85, 819 were age 85 to 90, and 386 were older than age 90. Patients age 75 or older were more likely to be women with permanent atrial fibrillation and comorbid conditions, such as hypertension and previous stroke. Vitamin K antagonist therapy was not as common as antiplatelet therapy in the elderly group.

As patients' age increased, so did event rates of death, stroke/thromboembolism, stroke/thromboembolism/death, and major bleeding. However, while risk for death and stroke/thromboembolism increased with age, risk for major bleeding did not. In patients younger than 75 years, vitamin K antagonist treatment was associated with lower mortality (adjusted hazard ratio, 0.57; 95% CI, 0.45 to 0.72), with an effect size that was maintained with increasing age strata (P=0.67 for the interaction).

Benefit was also found for the composite outcome of stroke/thromboembolism/death in patients younger than 75 years (adjusted hazard ratio, 0.69; 95% CI, 0.57 to 0.83), and again the effect size was maintained with increasing age strata (P=0.58 for the interaction). No statistically significant difference was seen between age strata for major bleeding (P=0.67 for the interaction). Age (P=0.0002) and previous stroke (P<0.0001) were the main predictors of stroke and thromboembolism in elderly patients, while renal impairment (P<0.0001) and use of vitamin K antagonists (P<0.004) were the predictors of major bleeding.

The authors pointed out that they did not have data on international normalized ratios and that their findings may not be generalizable to nonhospitalized patients or to other ethnic groups, among other limitations. They noted that elderly patients with atrial fibrillation have a high risk for death, stroke/thromboembolism, and major bleeding and that the relative benefit of reduction in stroke and vascular events with vitamin K antagonist use increased with age while the effect of aspirin declined.

“Indeed, the highest risk patients derive the greatest net clinical benefit when balancing ischemic stroke reduction against serious bleeding when [vitamin K antagonists] are used, and this may be even greater if non-[vitamin K antagonist] [oral anticoagulants] were used,” they wrote. They concluded that although elderly patients with atrial fibrillation have a higher risk for stroke and bleeding with vitamin K antagonist therapy than younger patients, the therapy has benefits for stroke/thromboembolism and mortality regardless of patients' increasing age.