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Amiodarone in atrial fibrillation
  1. O M P JOLOBE
  1. Department of Medicine for the Elderly
  2. Tameside General Hospital
  3. Ashton under Lyne OL6 9RW, UK
    1. YTSHAK KREISS,
    2. YECHEZKEL SIDI,
    3. HANAN GUR
    1. Department of Medicine C, The Chaim Sheba Medical Center, Tel Hashomer 52621, Israel

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      Sir,The study reported by Kreiss and co-workers1 is a major step in endorsing as good practice what junior doctors have been doing for sometime when faced with a heart failure patient in atrial fibrillation (AF), when the duty anaesthetist is unwilling to administer a general anaesthetic for electrical cardioversion. My only criticism is the implied message that the success rate of chemical cardioversion with amiodarone by the oral route, might be unacceptably low when attempted >48 hours after onset of AF. For such patients, the success rate of an exclusively oral regime has been shown to be of the order of 31%.2

      I have successfully cardioverted 16 out of 54 patients with amiodarone in the past 10 years, aged between 73 and 91 years (nine women), who illustrate the point that AF, documented on at least two occasions, more than 48 hours before initiation of anti-arrhythmic therapy, can be converted to sinus rhythm with amiodarone, with no relapse on follow-up of up to 5 years. Prior to amiodarone, the duration of AF was 4–35 days in eight patients, 8–22 weeks in five patients, one year each in two patients, and 3 years 4 months in the final patient. After receiving a standardised loading dose (most of which was administered on an out-patient basis) of amiodarone 600 mg/day for 7 days, followed by 400 mg/day for 7 days, with a subsequent maintenance dose of 200 mg/day, cardioversion was documented by electrocardiography at variable times, ranging from <14 days (five cases) to periods of up to nine and a half months (11 cases), depending on when the patient could attend for follow-up. Subsequent to successful cardioversion, seven patients have remained in sinus rhythm during follow-up lasting 1–5 years, whilst in another nine, follow-up in sinus rhythm has been of <1 year duration. One case strikingly illustrates the risk/benefit profile of warfarin vs chemical cardioversion with amiodarone, even when the latter is commenced after 48 hours. This was a 74-year-old woman who commenced warfarin as well as amiodarone after a transient ischaemic attack occurring after five and a half months of established AF. Whist on warfarin, she experienced a near-fatal anaphylactic reaction to a 500 μg dose of intravenous vitamin K (Konakion Roche),3 administered for correction of a prolonged International Normalised Ratio (INR). As a result of this mishap, instead of using the intravenous route, a subsequent INR of 9.5 was corrected to 1.7, within 24 hours, through the use of a 5 mg dose of oral vitamin K. After 5 months treatment with 200 mg/day of amiodarone, this patient has recently reverted to sinus rhythm, and will shortly be stopping warfarin, thereby avoiding all the risks of long-term anticoagulation.

      References

      This letter was shown to the authors who responded as follows:

      Sir,The main aim of our study was to prospectively examine the efficacy and safety of intravenous amiodarone in recent onset atrial fibrillation (AF).1-1 The study did not include patients with AF of more than 48 hours duration, and thus, we have not tried to directly imply any message about the efficacy of amiodarone conversion in such patients. However, we agree with Dr Jolobe, that converting chronic AF with oral amiodarone is feasible, but should be administered after appropriate anticoagulation. Dr Jolobe's success rate of about 30% conversion is in accordance with previous published data on treatment of AF with amiodarone.1-2 Moreover, as shown in our data, we achieved similar results, as continued oral amiodarone loading for one month was successful in 3/9 patients.1-1However, it should be noted that intravenous amiodarone, but not oral loading, has an immediate effect on slowing the ventricular response rate, as we and others have shown. Thus, the indications and the risk-benefit ratio are different for intravenous vsoral amiodarone.

      References

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