American physicians treating patients with atrial fibrillation, a type of arrhythmia or irregular heartbeat that can lead to stroke, are slow to incorporate newer medications into their practice, according to a study from the Massachusetts General Hospital (MGH). The report in the Oct. 26 issue of Archives of Internal Medicine looked at physicians' rates of prescribing two types of antiarrhythmic medications and found that older medications continue to be used in most patients, even though newer options may be more effective and have fewer side-effects. They also found that overall usage of these medications may be too low.
"Physician's practices appear to be guided more by tradition than by the latest science," says Randall Stafford, MD, PhD, of the MGH Institute for Health Policy and General Medicine Division, who led the study. "We think our study points out the need for better treatment guidelines and physician education."
Atrial fibrillation, an abnormal rhythm in the contraction of the upper chambers of the heart, is the strongest common risk factor for stroke. Antiarrhythmic medications, which directly address heart rhythm problems, fall into two categories: rate control medications, which slow the irregular heartbeat, and sinus rhythm medications, which attempt to restore normal heart rhythm.
The research team used data from the National Ambulatory Medical Care Survey from 1980 to 1996 to track trends in prescribing antiarrhythmics. Based on information from 1,555 office visits by patients with atrial fibrillation, they found an overall decrease in prescriptions for both kinds of drugs. Prescriptions for rate control drugs dropped from 79 percent of visits in 1980-81 to 62 percent in 1994-96. Sinus rhythm drugs were prescribed in 18 percent of 1980-81 visits, dropped to 4 percent in 1992-93, but then increased to 13 percent in 1994-96.
Among prescriptions for rate control drugs, digoxin (digitalis) continues to be the most commonly prescribed drug, although prescriptions for beta blockers and calcium channel blockers increased during the study period. Digoxin, the research team noted, has several limitations not found in beta blockers and calcium channel blockers. For example, patients taking digoxin may be more likely to experience shortness of breath when they exert themselves.
Among sinus rhythm drugs, a group of older drugs called class IA drugs were the most frequently prescribed. The significant dip in usage of sinus rhythm drugs in 1992-93 was probably due to a 1989 report of serious side effects from some sinus rhythm medications. New sinus rhythm medications with fewer side effects "class III drugs" have been introduced in recent years. However, most of the increase in usage of sinus rhythm drugs seen between 1992-93 and 1994-96 reflected greater use of the older class IA drugs.
"While there are good reasons to be cautious about adopting new medications, these results imply an inherent inertia in physician practices that does not reflect the most recent scientific information," Stafford says. "It's interesting to note that the drop in usage of class IA sinus rhythm agents after problems were reported was much more dramatic than the rate at which newer medications have been adopted. It appears that physicians react more quickly to reports of toxic reactions than they do to news of a medication's effectiveness."
Other authors of the Archives study are Daniel Singer, MD, Deborah Robson and Bismruta Misra, MPH, of the MGH General Medicine Division; and Jeremy Ruskin, MD, of the MGH Cardiac Unit. The study was supported by grants from the National Heart, Lung and Blood Institute and the Eliot B. Shoolman Fund at the MGH.