Three-dimensional vector ECG analysis in the diagnosis of the left bundle branch block

The complete left bundle branch block (CLBBB) leads to the development of severe heart failure and requires resynchronization therapy(CRT). It is known that one third of patients do not respond to CRT. In this regard, it is necessary to search new diagnostic criteria for patient selection for CRT.

Aim. Determination of the criteria for CLBBB using three-dimensional vectorcardiography data with analysis of the rate of vector loop formation.

Material and research methods. The study included 137 patients. The main group consisted of 57 patients with CLBBB, which was based on D. G. Strauss et al. (2011) criteria. Causes of CLBBB and comorbidities were not considered. The control group included 80 healthy individuals. All patients underwent synchronous registration of 12 standard ECG leads and reconstruction of a three-dimensional vectorcardiogram (VCG) using the McFee-Parungao system.

Research results. The following signs are characteristic for CLBBB according to three-dimensional VCG data: • fracture of the spatial vector loop due to a change in the direction of the excitation front in its middle part; • reduction in planarity index (PI) less than 80%; • a sharp, by a factor of 2 or more, decrease in the speed of tracing a spatial vector loop in its middle part with the formation of a “claw-shaped” curve with two peaks R and L.

Conclusion. Three-dimensional VCG allows you to reliably determine the «true» CLBBB, based on the “fracture” of the spatial vector loop with a reduction in PI less than 80% and a significant decrease in the speed of tracing the vector loop in its middle part with the formation of a “clawshaped” curve and carry out a differential diagnosis with “false” СLBBB, in which changes on the ECG are associated with a combination of left ventricular hypertrophy and left anterior fascicular block, when there is no “fracture” of the loop, a reduction in PI, and the routing speed decreases at the end of the loop without forming a “claw-shaped” curve.

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