Arq. Bras. Cardiol. 2024; 121(12): e20240767

The Importance of Electrovectorcardiographic Assessment of Intraventricular Blocks and their Relationship with the Cardiac Cycle

Carlos Alberto Pastore

DOI: 10.36660/abc.20240767i

This Short Editorial is referred by the Research article "Impact of Intraventricular Blocks on Cardiac Cycle Dynamics: An Echocardiographic and Vectorcardiographic Analysis".

The impact of intraventricular conduction disorders on myocardial activation and ventricular function has long been debated. However, with the advent of cardiac resynchronization therapy, this topic has gained even more attention during the last two decades.^,

At that time, our team utilized surface electrocardiographic mapping and isochronal line maps to assess the mean activation time in three specific regions of the heart: the right ventricle (RV), the left ventricle (LV), and the anteroseptal region. This evaluation was conducted on patients with a left ventricular ejection fraction of less than 40%, who exhibited left bundle branch block (LBBB), and had a mean QRS duration of 180 ms.^, The cardiac electrical activation was evaluated in three groups of patients: 1) patients with native LBBB, 2) patients under RV pacing, and 3) patients under biventricular pacing (BVP). In individuals with LBBB, the RV and anteroseptal mean activation time were delayed compared to the LV, leading to a loss of synchrony. Similarly, the RV pacing group’s activation time extended beyond normal, with a more significant difference between the septal area and LV. LV and RV activation times were similar during BVP, and the septal activation approached the normal and native LBBB conditions. Those findings suggested that the prolonged RV electrical activation by BVP, which sometimes may go unnoticed in the presence of LBBB, could be a relevant criterion in selecting candidates for cardiac resynchronization therapy.^,

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