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MINI-FOCUS ISSUE: BRUGADA SYNDROME: CLINICAL RESEARCH

Longer Repolarization in the Epicardium at the Right Ventricular Outflow Tract Causes Type 1 Electrocardiogram in Patients With Brugada Syndrome

Departments of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan.

Manuscript received May 4, 2007; revised manuscript received September 24, 2007, accepted October 17, 2007.

^_* Reprint requests and correspondence: Dr. Satoshi Nagase, Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8558, Japan. (Email: snagase{at}cc.okayama-u.ac.jp).

Objectives: We examined the relationship between repolarization abnormality and coved-type ST-segment elevation with terminal inverted T-wave (type 1 electrocardiogram [ECG]) in patients with Brugada syndrome (BrS).

Background: Recent experimental studies have suggested that accentuation of the right ventricular action potential (AP) notch preferentially prolongs epicardial AP causing inversion of the T-wave.

Methods: In 19 patients with BrS and 3 control subjects, activation-recovery intervals (ARIs) and repolarization times (RTs) in the epicardium and endocardium were directly examined with the use of local unipolar electrograms at the right ventricular outflow tract. Surface ECG, ARI, and RT were examined before and after administration of pilsicainide.

Results: Type 1 ECG was observed in 10 of the 19 BrS patients before the administration of pilsicainide and in all of the 19 patients after the administration of pilsicainide. We found that ARI and RT in the epicardium were shorter than those in the endocardium in all 9 BrS patients without type 1 ECG under baseline conditions and in all control subjects regardless of pilsicainide administration. However, longer epicardial ARI than endocardial ARI was observed in 8 of the 10 BrS patients manifesting type 1 ECG under baseline conditions and in all of the BrS patients after the administration of pilsicainide. Also, epicardial RT was longer than endocardial RT in all patients manifesting type 1 ECG regardless of pilsicainide administration.

Conclusions: Our data provide support for the hypothesis that the negative T-wave associated with type 1 BrS ECG is due to a preferential prolongation of the epicardial AP secondary to accentuation of the AP notch in the region of the right ventricular outflow tract.

Abbreviations and Acronyms   ARI = activation-recovery interval   ARIc = activation-recovery interval corrected for heart rate   AT = activation time   BrS = Brugada syndrome   ECG = electrocardiogram   RT = repolarization time   RVOT = right ventricular outflow tract   V1(3ics) = surface ECG lead V1 at the third intercostal space   V2(3ics) = surface ECG lead V2 at the third intercostal space   V1(4ics) = surface ECG lead V1 at the fourth intercostal space   V2(4ics) = surface ECG lead V2 at the fourth intercostal space   VF = ventricular fibrillation

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