Analysis of QRS alterations during stress test recordings on patients with brugada syndrome

Brugada syndrome (BrS) is characterized by the occurrence of syncope and sudden cardiac death due to cardiac arrhythmia, in patients with apparently structural normal heart. A study population of 46 patients with suspected or diagnosed BrS was analyzed. Six patients presented clinical symptoms, 13 patients did not present any clinical symptoms, and 27 were negatively diagnosed of having the syndrome. Stress test ECG recordings were analyzed for all the patients by evaluating a QRS-angle index during the entire duration of the test. Changes in these angles, measured at different stages of the test were statistically compared among the three patient groups. The R-wave angle showed its highest changes in augmented leads aVL (-11.9°± 10.9°) and aVR (-7.9°± 11.7°) at the time of maximum effort. Similar changes were observed in both asymptomatic and control groups, but slightly different to the symptomatic group, in particular during the active (AR) and passive (PR) recovery phases. Statistically significant differences were found between symptomatic and asymptomatic groups in such phases (AR: p=0.0125, PR: p=0.0194 in aVR), but not between asymptomatic and non-diagnosed BrS subgroups (AR, p=0.2039, PR: p=0.5826). This study shows that morphologic changes during depolarization induced by stress test are associated with the symptomatic BrS, particularly during the recovery phases.