ABC | Volume 113, Nº1, July 2019

Review Article Pastore et al ECG/VCG in the current clinical practice Arq Bras Cardiol. 2019; 113(1):87-99 Figure 2 – Electrical activation of the heart and its projection in the three spatial planes, thus giving origin to the vectorcardiographic loops in the respective planes. The VCG complements the ECG in the analysis of acute myocardial infarctions andmakes the differential diagnosis of the associations with blocks and chamber hypertrophies. There is no doubt that the most ordinary situations in the cardiological routine, such as absent or exaggerated R waves from V1 to V3, require a more sophisticated definition in this region that depicts many expressions of different pathologies. Therefore, in this region the ECG/VCG is capable of characterizing the presence of: 22-27 (Figures 5B, 6[A, B, C and D]) a) Left anteromedial fascicular block (LMFB) b) Right ventricular hypertrophy (RVH) c) Lateral infarction d) Ventricular pre-excitation syndrome (WPW) e) Brugada syndrome The ECG/VCG is the gold standard to identify complete and fascicular blocks, because it can differentiate them either in isolation or in association with other blocks. The electrical path marked by the ventricular activation loops can identify the blocks, as well as other associations. 21,23,28 (Figure 7) The end-conduction delays, previously denominated incomplete right bundle-branch blocks, are neatly defined by the ECG/VCG. These findings can be mistaken for the left phenomena and also can mimic a myocardial infarction area. Thus, the association of ECG/VCG solves the doubts that arise from the presence of these delays, which can be either the variants from the normal, or even suggest a conduction disorder in specific areas of the right ventricle. The presence of the end-conduction delay (ECD) is clarified in the ECG/VCG by the S 1 S 2 S 3 pattern, with the S wave in D 2 greater than the one in D 3 , qR in aVR and presence of S wave from V 1 to V 6 . The ECG/VCG confirms the ECD position backwardly and to the right in the transverse plane, and upwardly and to the right in the frontal plane. 25 (Figure 8) One of the definitive identifications obtained by the ECG/VCG association is that of the presence of a ventricular pre‑excitation (WPW). The presence of the delta wave is very clearly seen in the beginning of the QRS loop by the proximity of the comets at the onset of the QRS loop, characterizing the delay caused by the accessory pathway, thus also establishing the position of the anomalous bundle at the valvular annulus. 26 (Figure 9 [A and B]) One of the most recent diagnostic achievements of the ECG/VCG refers to the criteria to establish Brugada syndrome patterns, as well as the early repolarization (ER) phenomenon. It is important to emphasize that, in typical cases, there are no difficulties to make the electro‑vectorcardiographic identification of both conditions. Due to the severity of the first, to the variability of the second between normal cases and other pathologies, and also to the possibility of having an early repolarization pattern located in a more anterior area, it became essential to make an adequate distinction between them. From the ECG/VCG viewpoint, there are no guidelines set to date to identify J-wave abnormalities. Specific ECG/VCG patterns of the J-wave abnormalities, namely the Brugada syndrome (BrS), and the early repolarization pattern (RP) were studied by our research team. An important qualitative and quantitative analysis of the ECG/VCG was carried out in all the study population, specifically regarding aspects of the area comprising the terminal portion of the QRS loop, the J point and the ST segment. This analysis showed a neat end-conduction delay (ECD) in all the individuals (in both the BrS and the RP groups). This ECD is characterized by a conduction delay greater than 10 ms at the final portion of the QRS in all the planes, either to the right or to the left (slowing of the comets, which tend to get closer and, eventually, to merge). 89