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MINI-FOCUS ISSUE: BRUGADA SYNDROME: CLINICAL RESEARCH

Ventricular Repolarization Restitution Properties in Patients Exhibiting Type 1 Brugada Electrocardiogram With and Without Inducible Ventricular Fibrillation

Cardiology Department, Lariboisière Hospital, Paris, France.

Manuscript received August 21, 2007; revised manuscript received November 9, 2007, accepted November 12, 2007.

^_* Reprint requests and correspondence: Dr. Fabrice Extramiana, Cardiology Department, Lariboisière Hospital, 2 rue Ambroise Paré, 75475 Paris Cedex 10, France. (Email: fabrice.extramiana{at}lrb.ap-hop-paris.fr).

Objectives: This study aimed to elucidate the contribution of the repolarization restitution property to the sustained ventricular fibrillation (VF) in Brugada syndrome.

Background: Although phase 2 re-entry develops as the trigger of VF, the other precipitating factors have remained unclear.

Methods: Twenty-one patients with a type 1 Brugada electrocardiogram underwent programmed electrical stimulation. Before the VF induction, single extrastimuli were delivered at 3 basic drive cycle lengths (BCLs) (400 ms, 600 ms, and 750 ms) from the right ventricular apex (RVA) and outflow tract (RVOT), and the activation recovery interval (ARI) was measured at 5-mm vicinity of the pacing site. The maximum ARI restitution slope was determined using the overlapping least-squares linear segments.

Results: We found that VF was inducible in 10 patients. A repeated-measure analysis of variance revealed that the slope in the RVA was steeper in patients with inducible VF than in those without but that in the RVOT was similar. The slope was steeper at longer BCLs and also steeper in the RVA than RVOT at BCLs of 600 and 750 ms. In patients with inducible VF, the percentage of patients exhibiting a slope >1 was 0%, 20%, and 75% in the RVA and 0%, 0%, and 14% in the RVOT at BCLs of 400 ms, 600 ms, and 750 ms, respectively. No patients without inducible VF had a slope >1.

Conclusions: These results suggest the repolarization restitution property is a contributing factor to the propensity for VF in Brugada syndrome and, regarding this property, the RVA plays more important role than the RVOT.

Abbreviations and Acronyms   ANOVA = analysis of variance   APD = action potential duration   ARI = activation recovery interval   BCL = basic drive cycle length   DI = diastolic interval   PES = programmed electrical stimulation   RVA = right ventricular apex   RVOT = right ventricular outflow tract   VF = ventricular fibrillation

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