Aims:Amiodarone is the gold standard medication to control heart rate in critically ill patients with atrial tachyarrhythmias (AT). However, effective doses and covariates influencing its efficacy remain unknown. We therefore performed pharmacodynamic modeling of heart rate reduction induced by amiodarone in these patients.
Methods-Results:This observational study included 80 consecutive severely ill patients receiving amiodarone to treat atrial tachyarrhythmias. A total of 1348 timeheart rate observations with 361 amiodarone dose administrations were analyzed during up to 6 days after hospital treatment initiation using a nonlinear mixed effect model. Pretreatment with amiodarone before intensive care administration, paroxysmal versus persistent AT, catecholamine infusion, fluid and magnesium loading were among covariates assessed in the model.In case of paroxysmal AT in a patient not pretreated by amiodarone, a 300 mg intravenous loading dose combined with a 800 mg oral dose on the first day followed by 800 mg/day p.o. for 4 days was effective to achieve a heart rate between 80 and 115 bpm within the first day and to maintain it during the next 4 days. Corresponding doses were twice as high in patients with persistent AT. Use of intravenous magnesium (p<0.02) and fluid loading (p<0.02) was associated with an earlier and greater heart rate decrease. Dobutamine use had an opposite influence (p<0.05).
Conclusions:In critically ill patients with AT, dose of amiodarone required to control heart rate is influenced by the type of AT and by other easily measurable conditions which may allow better individualization of amiodarone dosing.
Ablation of posteroseptal accessory pathways specifically in children carries a risk of coronary artery injury which is probably underestimated. The use of merged 3D images and coronary angiograms, the reduction of RF energy or the switch to cryoablation are possible alternatives to limit the risk of coronary injury.
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