Bacharova Ljuba, Szathmary Vavrinec, Mateasik Anton
International Laser Center, Bratislava, Slovakia.
J Electrocardiol. 2011 Nov-Dec;44(6):768-78. doi: 10.1016/j.jelectrocard.2011.03.007. Epub 2011 Jun 11.
By definition, the electrocardiographic (ECG) patterns of left bundle-branch block (LBBB) represent distinctive changes in duration and shape of the QRS complex caused by intraventricular conduction delay in the left ventricle (LV) due to structural abnormalities in the His-Purkinje conduction system and/or ventricular myocardium. However, impaired conduction in the working myocardium is not taken into consideration in the practical ECG diagnosis. Because the degree of LV myocardium impairment could be of importance for clinical evaluation of patients, we studied the effects of blocked and of delayed onsets of activation in the LV to simulate complete and incomplete LBBBs and slowed conduction in the LV myocardium by applying an analytical computer model. We demonstrated that typical LBBB patterns were caused both by block or delay in the onset of the LV activation, as well as by impaired conduction in the myocardium itself while maintaining the location and onset of the LV activation. The most important difference was the absence of initial anteriorly oriented electrical forces in cases of the simulated complete LBBB and of incomplete LBBB if the onset of LV activation was delayed (≥ 6 milliseconds). Under the conditions defined in this model that did not consider myocardial infarction, the presence of initial anteriorly oriented electrical forces was indicative of preserved conduction in the left bundle and of impaired conduction in LV working myocardium.
The elucidation of the participation of working myocardium impairment in the intraventricular conduction delay in the LV could be of vital significance for the clinical management of patients with LBBB patterns, for example, indicated for resynchronization therapy.
根据定义，左束支传导阻滞（LBBB）的心电图（ECG）模式代表了由于希氏 - 浦肯野传导系统和/或心室心肌的结构异常导致左心室（LV）室内传导延迟而引起的QRS波群持续时间和形态的独特变化。然而，在实际的心电图诊断中并未考虑工作心肌的传导受损情况。由于左心室心肌损伤程度对于患者的临床评估可能很重要，我们通过应用一个分析计算机模型来研究左心室激活受阻和延迟激活的影响，以模拟完全性和不完全性LBBB以及左心室心肌传导减慢的情况。我们证明，典型的LBBB模式既由左心室激活起始的阻滞或延迟引起，也由心肌自身的传导受损引起，同时保持左心室激活的位置和起始时间。最重要的区别在于，如果左心室激活延迟（≥6毫秒），在模拟的完全性LBBB和不完全性LBBB病例中不存在初始向前的电力。在该模型定义的不考虑心肌梗死的条件下，初始向前电力的存在表明左束支传导正常且左心室工作心肌传导受损。
阐明工作心肌损伤在左心室室内传导延迟中的作用对于LBBB模式患者的临床管理可能具有至关重要的意义，例如，对于心脏再同步治疗的指征。
