Local Filtered QRS Duration during Sodium-channel Blockade in Brugada Syndrome Patients

The Brugada syndrome is associated with sodium channel dysfunction and the characteristic ST segment elevation is thought to arise from the right ventricle. We hypothesized that sodium channel blockade in Brugada syndrome patients cause more activation delay in leads overlying the right ventricle than in other leads. ECG data were recorded during infusion of a sodium channel blocker in 17 family members of Brugada syndrome patients. Signal averaged and filtered signals from a number of body surface leads were investigate for small potentials that are generated by myocardium close to the recording electrode. ST segment elevation in V1 during sodium channel blockade was accompanied by pronounced activation delay in VI after the end of the QRS complex in lead II (32 +/- 18 ms), whereas activation in V6 was not later than end of QRS (12 +/- 13 ms). The latest activation in V1 was delayed to a greater extend than in control patients without ST elevation during sodium channel blockade (151 +/- 17 ms vs 128 +/- 10 ms, p <0.005). We conclude that the activation of the right ventricle in Brugada syndrome patients is more sensitive to sodium channel blockade compared to the left ventricle and compared to patients without ST segment elevation