Brugada syndrome (BS) is characterized by a typical ECG pattern. To carrying out the diagnosis in patients without a spontaneous ECG pattern, sodium channel blocker (SCB) is used. However, the value of this test is not well known, particulary its sensibility because of a complex genetic model do not allowing the use of any mutation as a gold standard. To clarify the value of this test, we analyzed a database of 680 SCB performed in families affected by the syndrome, considering the mandatory transmitters (MT) as a true positive.

All patients who underwent a SCB and belonging to a family with at least 2 subjects with the syndrome were included. The MT was defined by an individual with at least one descendant in the first degree and an ascendant with a BS or unexplained sudden cardiac arrest. All the ECG data at baseline and at diagnosis was reviewed by two expert, blinded to the clinical and genetical status.

Of the 137 selected families, 85 MT were identified. Excluding individuals who have not benefited from the SCB, sensitivity of test was calculated at 91% (42/46). According to the molecule used, the sensitivity was significantly better for ajmaline than flecainide with a sensitivity of 97% and 75% respectively (p=0.048). Among the 680 individuals who benefited a SBC, the duration of the S wave in DII, DIII and V5 and the R wave in aVR were significantly elongated at both baseline and diagnosis, in individuals with a positive SBC. Complications occurred in 1.6% of patients (11/680) including 4 required an electrical cardioversion. Risk factors present a complication was the youngest age and the occurrence of a complication with a member of his family.

This study demonstrates for the first time, the excellent sensitivity of SCB in BS, particulary with the use of ajmaline. Complications are rare and doesn’t appeared to be linked with QRS enlargement but with familial history of ventricular arythmia during the test