Low doses of amiodarone, a drug used to
treat irregular heartbeats, significantly reduce the number of recurrences of
atrial fibrillation (AF), the most common irregular heart rhythm.
Even when corrected, "atrial fibrillation recurs within 3 to 6 months in at
least one half of treated patients," according to Dr. Denis Roy from the
Montreal Heart Institute in Montreal, Canada, and associates in the Canadian
Trial of Atrial Fibrillation.
The authors compared amiodarone with sotalol or propafenone, two other drugs
for irregular heart rhythms, in treating 403 patients with AF at 19 heart
centers in Canada. Their results are published in the March 30th issue of The
New England Journal of Medicine.
Patients whose AF returned had to be treated with electrical cardioversion
-- an electrical shock to the chest wall. Fewer of the 201 amiodarone patients
required electrical cardioversions during the first 21 days of treatment than
the 202 sotalol or propafenone patients, the results indicate.
During an average follow-up period of nearly 16 months, 35% of the
amiodarone patients experienced an episode of AF, compared with 63% of the
patients assigned to sotalol or propafenone, the authors report. Half the
sotalol and propafenone patients experienced a recurrence within 98 days of the
beginning of treatment.
Overall, the patients in the amiodarone group were less than half as likely
to experience a recurrence as the patients in the other groups, the
investigators write. Only 8% of the amiodarone patients discontinued treatment
because of a lack of effectiveness, compared with 28% of the sotalol and
propafenone patients. On the other hand, side effects (mostly gastrointestinal
complaints) led to discontinuation of treatment among more amiodarone patients
(18% versus 11%).
"The difference in efficacy we observed is striking; amiodarone was about
twice as effective as two commonly used antiarrhythmic agents in preventing
recurrences of atrial fibrillation," Roy and colleagues conclude. "Our findings
indicate that amiodarone warrants consideration as first- or second-line therapy
in patients in whom maintenance of (normal heart) rhythm is desired."
