New Bisphosphonate May Increase Risk of Arrhythmias: Presented at ASBMR

By Em Brown

HONOLULU, HAWAII -- September 25, 2007 -- The investigational bisphosphonate zoledronic acid appears to more than double the risk of atrial fibrillation and other arrhythmias, investigators reported here during the 29th Annual Meeting of the American Society for Bone and Mineral Research (ASBMR).

Results of the Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly-Recurrent Fracture Trial (HORIZON-RFT) show that this agent significantly increased bone mineral density (BMD) when given once a year by intravenous infusion.

Results of a substudy of HORIZON-RFT were reported by principal investigator Steven R. Cummings, MD, Professor of Medicine, University of California at San Francisco's School of Medicine, San Francisco, California, United States.

In his presentation, Dr. Cummings said the substudy results indicate that zoledronic acid also doubled the risk of atrial fibrillation.

The substudy looked at 7,714 postmenopausal women enrolled in HORIZON; it excluded elderly participants who were part of the larger study.

Patients were evaluated for risk factors for atrial fibrillation, which included congestive heart failure (CHF), tachyarrhythmia, older age, and previous use of bisphosphonates.

The incidence of atrial fibrillation was 2.2% among patients with a history of antihypertensive medication use compared with 1.6% among nonusers, Dr. Cummings reported.

Zoledronic acid had a hazard ratio (HR) of 2.35 overall, 1.81 for past antihypertensive medication use, 2.86 for CHF, and 6.01 for tachyarrhythmias. There was an increase in risk of 1.07 for every year on zoledronic acid treatment.

"Women who have previously used bisphosphonates might have an increased risk for atrial fibrillation [with zoledronic acid therapy]," Dr. Cummings warned. This has been observed in studies of alendronate and early data here suggest it may also hold true with zoledronic acid. "This possibility needs additional investigation."

Funding for this study was provided by Novartis.


[Presentation title: Risk Factors for Serious Adverse Events (SAEs) of Atrial Fibrillation in the HORIZON-PFT Trial of Zoledronic Acid. Abstract 1056]