IJCS | Volume 33, Nº3, May / June 2020

268 Figure 3 - QTc evolution in the true positive group from rest (baseline QTc dispersion) to effort (peak QTc dispersion) conditions. QTc Baseline QTc Peak QTc Figure 4 - QTc evolution from rest (baseline QTc) to effort (peak QTc) conditions in the false positive group. QTc Baseline QTc Peak QTc of using the QTd (within the first minute of recovery and/or rest) for the diagnosis of significant coronary disease. Based on previous studies, we hypothesized that coronary obstructionwould lead to prolonged action potential in the ischemic region, and that such increase could be identified by the QTd. Actually, it would reflect in theory the difference between repolarization in the ischemic region compared to the non-ischemic in the ventricular syncytium. The first result that will be discussed concers the reproducibility of QT dispersion measurements. One of the major problems concerning QT interval measurements is the difficulty in obtaining acceptable interobserver variability. In our study, interobserver Barcelos et al. QT interval dispersion in exercise test Int J Cardiovasc Sci. 2020; 33(3):263-271 Original Article