Applicability of the Electro-Vectorcardiogram in Current Clinical Practice

Abstract

The electrocardiogram (ECG) has been reinvigorated by the identification of electrical alterations that were not definitely clarified before. In this context, and mainly regarding the definition of arrhythmogenic substrates, the association of the ECG with the vectorcardiogram (VCG) has gathered much more information about the cardiac electrical phenomena, thus allowing us to differentiate potentially fatal cases from benign ones. Obtaining a VCG concomitantly with the performance of an ECG has led to a significant gain in the definition of extremely sophisticated pathologies, which function suffer some type of structural or dynamic alterations, involving either the reduction or enhancement of ionic channels and currents. The classic aspects of the ECG/VCG association in the differential diagnosis of myocardial infarctions, conduction disorders, atrial and ventricular hypertrophies, and the correlations between these electrical disorders are still valid and assertive. The association of these pathologies is further clarified when they are seen through the ECG/VCG dyad. The three-dimensional spatial orientation of both the atrial and the ventricular activity provides a far more complete observation tool than the ECG linear form. The modern analysis of the ECG and its respective VCG, simultaneously obtained by the recent technique called electro-vectorcardiogram (ECG/VCG), brought a significant gain for the differential diagnosis of some pathologies. Therefore, we illustrate how this type of analysis can elucidate some of the most important diagnoses found in our daily clinical practice as cardiologists.

Figure 1

Electrocardiogram vs. Vectorcardiogram.

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.

Figure 3

(A) Presence of myocardial infarction area in the inferior wall, with QRS vectorcardiographic loop onset oriented upwardly and to the left. (B) Aspect of a large myocardial infarction area from V1 to V6 and its respective loop in the transverse plane, with anomalous activation of the septum and exaggerated backward rotation, followed by deformation of the QRS loop.

Figure 4

Aspects of the VCG loops in the Inferior MI (in Fig. 3A of the previous item, note the QRS loop onset upwardly in the frontal plane, with more than 30 ms duration [15 comets]); in Figure 4A – LASFB, observe the QRS loop onset downwardly (through the posterior-inferior division), with counterclockwise rotation and the major portion of the loop oriented upwardly and to the left; and in Figure 4B - LASFB + inferior MI, the association of the two entities; note that the QRS loop in the frontal plane is directed upwardly, with clockwise rotation, and after 30 ms it changes its orientation, with counterclockwise rotation characterizing the LASFB.

Figure 5

Electro-vectorcardiographic aspects of LASFB - Fig. 4A of the previous item, left posteroinferior fascicular block (LPIFB) - Figure 5A and left anteromedial fascicular block (LAMFB) - Figure 5B.

Figure 6

Illustrations of differential diagnoses identified by the ECG/VCG in different pathologies: left anteromedial fascicular block (LAMFB) - see Fig.5B; right ventricular hypertrophy (RVH) - Figure 6A; lateral infarction - Figure 6B.

Figure 6

Illustrations of differential diagnoses identified by the ECG/VCG in different pathologies: left anteromedial fascicular block (LAMFB) - see Fig.5B; ventricular pre-excitation syndrome (WPW) - Figure 6C; Brugada syndrome - Figure 6D.

Figure 7

Vectorcardiographic aspects of the association of LPIFB and RBBB: axis to the right in the frontal plane (LPIFB), with most of the QRS loop in the frontal plane, oriented downwardly and to the left, and the QRS loop in the transverse plane, slowly ending forwardly and to the right (RBBB).

Figure 8

Electro-vectorcardiographic aspects of the end-conduction delay.

Figure 9

(A and B). Electro-vectorcardiographic aspects of the ventricular pre-excitation, highlighting the presence of the delta wave (arrows).

Figure 10

Characteristic electro-vectorcardiographic aspects of the early repolarization (ER) pattern: Transverse plane: QRS loop onset with counterclockwise rotation; the ECD began posteriorly and ended anteriorly and in the left quadrant in all ER patients. At the terminal segment of the QRS loop (now with clockwise rotation), 100% of the ER group showed, at the end of QRS loop, a “fishhook” pattern.

Figure 11

Electro-vectorcardiographic aspects found in ARVC, displaying the extremely long conduction delay at the end of the QRS loop.

Figure 12

Evolution of the electro-vectorcardiographic aspects after radiofrequency ablation over time in a patient with ECG-type 1 pattern of Brugada syndrome.