Time Course and Quantitative Analysis of AtrialFibrillation Episode Number and Duration AfterCircular Plus Linear Left Atrial Lesions. TriggerElimination or Substrate Modification: Early orDelayed Cure?

Kottkamp H, Tanner H, Kobza R, et al. J Am Coll Cardiol 2004;44:869 –77.

Study Question: Is there an abrupt or gradual reduction inatrial fibrillation (AF) after left atrial circular plus linearablation (LACLA)?Methods: The LACLA was performed under guidance of a3-dimensional electroanatomic mapping system in 100 pa-tients with paroxysmal (80) or persistent (20) AF. The left-and right-sided pulmonary veins were encircled, and linearablation lines were created between the circles and betweenthe mitral annulus and the left circle. Patients were treatedwith amiodarone or flecainide for 3 months post-LACLA,and a 7-day ambulatory recording was performed preabla-tion, immediately postablation, and at 3, 6 and 12 monthsof follow-up.Results: Preablation AF was present a mean of 35% of thetime. This was reduced to 26% immediately postablation,and to 8–11% at 3–6 months of follow-up. Freedom fromAF was present in the 7-day recording in 17% of patientspreablation, in 19% immediately postablation, and in 63%of patients at 12 months.Conclusions: The progressive reduction in AF burden afterLACLA indicates that the mechanism of action of this abla-tion technique is substrate modification, not the elimina-tion of triggers.Perspective: The strongest aspect of this study was theobjective quantification of AF burden with serial 7-dayambulatory recordings. However, although the delayedtherapeutic effect is consistent with substrate modificationdue to progressive lesion maturation, this finding by itselfdoes not rule out an equally important role for eliminationof triggers or autonomic denervation. FM

Use of Ibutilide in Cardioversion of Patients WithAtrial Fibrillation or Atrial Flutter Treated WithClass IC Agents

Hongo RH, Themistoclakis S, Raviele A, et al. J Am Coll Cardiol2004;44:864 – 8.

Study Question: Is the safety or efficacy of ibutilide affected bypretreatment with propafenone or flecainide?Methods: Ibutilide (1 or 2 mg) was infused in 71 patients(mean age 64 years) with atrial fibrillation (AF, 48) or atrialflutter (AFl, 23). All patients were being treated with

propafenone (300–900 mg/d) or flecainide (100–300 mg/d). The median duration of the AF/AFl episode was 2 days.The corrected QT interval (QTc) was measured before andafter cardioversion, and patients were monitored for 4 hafter ibutilide infusion.Results: The conversion rate was 74% for AF and 74% forAFl. The QTc increased by 20 ms to a mean of 462 mspost-ibutilide. Polymorphic ventricular tachycardia oc-curred in two patients (2.8%) after conversion to sinusrhythm.Conclusions: Both the efficacy and safety of ibutilide are notaffected by pretreatment with propafenone or flecainide.Perspective: There was no control group in this study, andthe conclusions are based on a comparison with previouslypublished data. Nevertheless, the study is clinically usefulbecause it suggests that, as is the case with amiodarone,pretreatment with propafenone or flecainide is not a con-traindication to chemical cardioversion with ibutil-ide. FM

Ibutilide Added to Propafenone for the Conversionof Atrial Fibrillation and Atrial Flutter

Chiladakis JA, Kalogeropoulos A, Patsouras N, Manolis AS. J AmColl Cardiol 2004;44:859 – 63.

Study Question: How safe and effective is ibutilide whenadministered to patients pretreated with propafenone?Methods: The subjects of this study were 104 patients withatrial fibrillation/flutter (AF/Fl) who failed to convert withpropafenone. Propafenone was administered as a single oraldose of 600 mg in 48 patients with paroxysmal AF/Fl, and ata daily dosage of 150 mg 3 times a day in 56 patients withchronic AF/Fl. Ibutilide (1 mg) was infused over 10 min andrepeated if necessary.Results: The conversion rate after ibutilide was 71% forparoxysmal AF/Fl and 62% for chronic AF/Fl. Polymorphicventricular tachycardia occurred in only one patient (1%)after ibutilide. None of the patients who converted to sinusrhythm with ibutilide had an immediate recurrence ofAF/AFl.Conclusions: Ibutilide is safe and effective when used inpatients with AF/AFl pretreated with propafenone.Perspective: This study is consistent with the results ofanother recent study and confirms that neither ibutilide’ssafety nor efficacy is compromised by pretreatment withpropafenone. The prevalence of immediate recurrence ofAF/AFl (IRAF) postcardioversion generally ranges from10–20%. In the electrophysiology laboratory, ibutilide hasbeen shown to suppress IRAF after transthoracic cardiover-sion. This study suggests that ibutilide exerts the samebeneficial effect when used in combination withpropafenone. FM

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ArrhythmiasAbstracts