Boston, MA - Prolongation of the P wave at signal-averaged electrocardiography (SAECG), sometimes used to identify patients susceptible to atrial fibrillation (AF) after cardiac surgery, can help select candidates for coronary artery bypass graft (CABG) surgery in whom amiodarone is likely to prevent the arrhythmia, according to a small randomized, placebo-controlled trial [1].

Dr Marco Budeus

The drug as given in the study reduced the one-week rate of post-CABG AF by about 40% compared with placebo, a benefit associated with significantly reduced hospitalization time and total per-patient costs, reported Dr Marco Budeus (University of Duisburg-Essen, Germany) and colleagues here at the Heart Rhythm Society 2006 Scientific Sessions.

The group used SAECG to screen 374 consecutive patients scheduled for isolated CABG and identified 110 with P-wave prolongation and so considered at increased risk for post-CABG AF. The high-risk patients were then randomized to receive amiodarone or placebo, with 600-mg/day amiodarone given orally before and for seven days after surgery. Actively treated patients also received the drug as a 300-mg IV bolus followed by a 24-hour postoperative IV infusion totaling 20 mg/kg. The two groups were similar with respect to clinical features and medications.

Amiodarone vs placebo: AF incidence and related hospitalization and cost

End point	Amiodarone, n=53	Placebo, n=53	p
Postoperative AF* (%)	34	85	<0.0001
ICU length of stay (d)	1.8	2.4	<0.05
Total hospitalization (d)	11.3	13.0	<0.03
Per-patient total cost (€)	18 400	19 300	<0.007

The rate of complications didn't differ significantly between the two treatment arms, and all events were clinically unimportant, Budeus told heartwire, adding that bradyarrhythmias developed in a handful of patients and one in each group required pacing.

Exploring possible reasons for the failure of amiodarone to suppress AF in about a third of the patients, the group saw that those who didn't develop the arrhythmia had achieved significantly higher amiodarone concentrations (p=0.02), according to Budeus. And the patients who stayed in sinus rhythm were significantly more likely to achieve levels >0.7 µg/mL (p<0.0001), which the literature suggests can be used as a threshold for effective amiodarone prophylaxis, he observed.