Assessment of the dynamic response of cardiac depolarization during stresstest recovery evaluated in patients with Brugada syndrome

Brugada syndrome is a genetic disease that may cause sudden cardiac death in patients with structurally normal heart. This study aims to assess dynamic response of cardiac depolarization to physical exercise, and particularly, during recovery phase. Several ECG depolarization features were studied including the R and S waves amplitude (Ra and Sa), the up-stroke and down-stroke of the R and S waves (Su, S
D
and S
S
) and their respective angles (α
R
and α
S
). Standard 12-lead ECG recordings were acquired during physical exercise test in 23 Brugada patients (11 symptomatic). By using a three-constant S-shaped function, we assessed the dynamics of the ECG markers by modeling their response during the recovery period. Brugada syndrome patients who were asymptomatic presented higher change values and faster change speed than symptomatic patients in several evaluated markers, especially in left precordial leads. On the other hand, symptomatic patients presented larger lag values as compared with asymptomatic patients. We concluded that dynamics of depolarization features, assessed during periods of increased parasympathetic tone, seems to be linked with the presence of symptoms in Brugada patients.