Fig 1.
A) Example of a QRS complex and the three QRS slopes analyzed in this study (red, blue and green lines). B) Temporal evolution of heart rate (upper panel) and the main extracted ECG markers (panels 2 to 4) evaluated in a representative BS patient during the whole exercise test. The major periods of the exercise test are marked in the upper panel of Fig 1B: exercise period (EX); recovery period (RE). Panel 1 also shows the phases at which the mean values were determined: the beginning of the exercise (EXbeg); the time of maximum effort (EXmax); the end of the entire recovery period (REend).
Fig 2.
a) and c) Temporal evolution of the S-wave amplitude () and heart rate (HR) during the exercise test for a male symptomatic patient; b) and d) for a male asymptomatic patient. The heart rate recovery (HRR) estimate and the change of
during exercise (
) are also shown. Thick vertical lines in black indicate the time of maximum effort (EXmax).
Table 1.
Baseline clinical characteristics of the Brugada syndrome population at the time of diagnosis.
Fig 3.
Mean ± SEM of the amplitude of the S wave (), the upstroke slope of the S wave (
) and the downstroke slope of the R wave (
), measured in different phases of the exercise test in leads V1 and V2.
Table 2.
Dynamic changes of depolarization markers between the exercise and recovery periods for symptomatic and asymptomatic patients.
Results are expressed in mean±SD. Statistically significant p-values were highlighted as follows: when comparing both groups during exercise, *(p < 0.05); when comparing both groups during recovery, † (p < 0.05), ‡(p < 0.01),§ (p < 0.005).
Table 3.
Model1: Logistic regression model using depolarization features selected by Lasso L1-regularization.
Table 4.
Model2: Logistic regression model using clinical and depolarization features selected by Lasso.
Fig 4.
Flowchart diagram of the processing pipeline used to obtain the different models investigated in the study.
Table 5.
Reduced models using only significant features from Table 4, before and after adjusting by confounding factors.
Only patients that underwent genetic screening were included (N = 79) in the first two models. The last two models included the whole population study (N = 110).
Fig 5.
a) Receiver operating characteristic (ROC) curves obtained for the two discriminative models summarized in Table 3 (Model1) and Table 4 (Model2), (b) for the reduced models adjusted () and non adjusted (Model2R_79) by mutation data, applied on the screened 79 patients, and c) for the reduced model using significant features from Table 3, adjusted (
) and non adjusted (Model2R_110) by BMI and ICD data. Solid circles in black represent the optimal operating points determining the sensitivity and specificity values from each ROC. AUC: area under the ROC curve (coloured areas); Se: sensitivity; Sp: specificity.