Bayés de Luna Antonio, Riera Andrés Pérez, Baranchuk Adrian, Chiale Pablo, Iturralde Pedro, Pastore Carlos, Barbosa Raimundo, Goldwasser Diego, Alboni Paolo, Elizari Marcelo
Institut Català Ciències Cardiovasculars, Barcelona, Spain.
J Electrocardiol. 2012 Sep;45(5):454-60. doi: 10.1016/j.jelectrocard.2012.06.002.
There are fibers in the left ventricle (LV) (LV middle network) that in around one third of cases may be considered a true septal fascicle that arises from the common left bundle. Its presence and the evidence that there are 3 points of activation onset in the LV favor the quadrifascicular theory of the intraventricular activation of both ventricles. Since the 70s, different authors have suggested that the block of the left middle fibers (MS)/left septal fascicle may explain different electrocardiographic (ECG) patterns. The 2 hypothetically based criteria that are in some sense contradictory include: a) the lack of septal "q" wave due to first left and later posteriorly shifting of the horizontal plane loop and b) the presence of RS in lead V(2) (V(1)-V(2)) due to some anterior shifting of the horizontal plane vectorcardiogram loop. However, there are many evidence that the lack of septal q waves can be also explained by predivisional first-degree left bundle-branch block and that the RS pattern in the right precordial leads may be also explained by first-degree right bundle-branch block. The transient nature of these patterns favor the concept that some type of intraventricular conduction disturbance exists but a doubt remains about its location. Furthermore, the RS pattern could be explained by many different normal variants. To improve our understanding whether these patterns are due to MF/left septal fascicle block or other ventricular conduction disturbances (or both), it would be advisable: 1) To perform more histologic studies (heart transplant and necropsy) of the ventricular conduction system; 2) To repeat prior experimental studies using new methodology/technology to isolate the MF; and 3) To change the paradigm: do not try to demonstrate if the block of the fibers produces an ECG change but to study with new electroanatomical imaging techniques, if these ECG criteria previously described correlate or not with a delay of activation in the zone of the LV that receives the activation through these fibers or in other zones.
左心室（LV）存在纤维（LV中间网络），约三分之一的病例中，这些纤维可被视为源自左束支共同主干的真正间隔束。其存在以及左心室有3个激活起始点的证据支持双心室心室内激活的四束支理论。自20世纪70年代以来，不同作者提出左中间纤维（MS）/左间隔束阻滞可能解释不同的心电图（ECG）模式。在某种意义上相互矛盾的两个基于假设的标准包括：a）由于水平面环先向左后向后移位导致间隔“q”波缺失；b）由于水平面向量心电图环向前移位，V（2）导联（V（1）-V（2））出现RS波。然而，有许多证据表明，间隔q波缺失也可由分支前一度左束支阻滞解释，右胸前导联的RS图形也可由一度右束支阻滞解释。这些图形的短暂性支持存在某种类型的心室内传导障碍这一概念，但对其位置仍存在疑问。此外，RS图形可由许多不同的正常变异解释。为了更好地理解这些图形是由于中间纤维/左间隔束阻滞还是其他心室传导障碍（或两者兼有），建议：1）对心室传导系统进行更多的组织学研究（心脏移植和尸检）；2）使用新方法/技术重复先前的实验研究以分离中间纤维；3）改变范式：不要试图证明纤维阻滞是否产生心电图变化，而是使用新的电解剖成像技术研究先前描述的这些心电图标准是否与通过这些纤维接受激活的左心室区域或其他区域的激活延迟相关。
