AF patients receive disparate medical therapy for stroke prevention

While pharmacotherapy for atrial fibrillation (AF) varies according to comorbidity and underlying risk, a study of Medicare Part D claims data showed that amiodarone was the most commonly prescribed antiarrhythmic agent at approximately 50 percent. The study appeared in the September issue of HeartRhythm.

“AF is a pervasive public health problem; its prevalence doubles with each decade of life and continues to increase,” wrote the study authors. “There are three therapeutic goals in the care of patients with AF: prevention of stroke, rate control and rhythm control.”

However, Jonathan P. Piccini, MD, MHS, of the Duke Clinical Research Institute in Durham, N.C., and colleagues pointed out there are limited data regarding nationwide patterns of pharmacotherapy for AF among older patients in the U.S. They used this analysis to better describe pharmacotherapy for AF among Medicare beneficiaries.

By using a 5 percent national sample of Medicare claims data, the researchers compared demographic characteristics, comorbidity and treatment patterns according to Medicare Part D status among patients with prevalent AF in 2006 and 2007. They also investigated pharmacotherapy for AF across risk strata, including medications for stroke prophylaxis, rate control and rhythm control.

Outpatient pharmacy charges for AF in the U.S. approach $600 million annually (Circ Cardiovasc Qual Outcomes 2011;4:313–320). In this analysis of more than 70,000 patients in a cohort of Medicare beneficiaries with AF, they found that patients enrolled in Medicare Part D were more likely to be women and black. Also, enrollees had greater comorbidity, including a higher frequency of heart failure.

In 2006, 27,174 patients (29.3 percent) with prevalent AF were enrolled in Medicare Part D. In 2007, enrollment increased to 49.1 percent.

Rate control with beta-blockers or nondihydropyridine calcium-channel blockers is a class I guideline recommendation for the management of patients with AF. Most enrollees were taking rate-control agents (74 percent in 2007). Beta-blocker use was higher in those with concomitant AF and heart failure and increased with higher CHADS₂ scores.
“Given that more than 50 percent of the cohort had heart failure and 60 percent had ischemic heart disease, it is surprising that beta-blocker use was not higher,” Piccini et al wrote. “When we examined medication use by heart failure status and CHADS₂ score, beta-blocker therapy was more frequent among patients with concomitant AF and heart failure and those with greater stroke risk.”

The researchers also reported that antiarrhythmic drug use was 18.7 percent in 2006 and 19.1 percent in 2007, with amiodarone (Cordarone, Pfizer) accounting for more than 50 percent—which is substantially lower than rates observed in large AF registries. Class Ic drugs were used in 3.2 percent of the patients in 2007. Warfarin use was less than 60 percent and declined with increasing stroke risk.

“This finding reiterates the well-recognized underuse of oral anticoagulation in patients with AF,” they wrote. “Although many patients may have had contraindications to warfarin or insufficient risk to warrant therapy, more than half of the beneficiaries had heart failure, one third had diabetes and more than 30 percent had cerebrovascular disease.

"The risk-treatment paradox observed with stroke prevention therapy in older Medicare Part D enrollees highlights the challenges of treatment decisions and reinforces the need for large comparative effectiveness studies in older patients,” the study authors concluded.