Section for Pathobiological Sciences, Department of Veterinary and Animal Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
Acta Physiol (Oxf). 2023 Mar;237(3):e13925. doi: 10.1111/apha.13925. Epub 2023 Jan 18.
The Purkinje fibers convey the electrical impulses at much higher speed than the working myocardial cells. Thus, the distribution of the Purkinje network is of paramount importance for the timing and coordination of ventricular activation. The Purkinje fibers are found in the subendocardium of all species of mammals, but some mammals also possess an intramural Purkinje fiber network that provides for relatively instantaneous, burst-like activation of the entire ventricular wall, and gives rise to an rS configuration in lead II of the ECG.
To relate the topography of the horse heart and the distribution and histology of the conduction system to the pattern of ventricular activation as a mechanism for the unique electrical axis of the equine heart.
The morphology and distribution of the cardiac conduction system was determined by histochemistry. The electrical activity was measured using ECG in the Einthoven and orthogonal configuration.
The long axis of the equine heart is close to vertical. Outside the nodal regions the conduction system consisted of Purkinje fibers connected by connexin 43 and long, slender parallel running transitional cells. The Purkinje fiber network extended deep into the ventricular walls. ECGs recorded in an orthogonal configuration revealed a mean electrical axis pointing in a cranial-to-left direction indicating ventricular activation in an apex-to-base direction.
The direction of the mean electrical axis in the equine heart is determined by the architecture of the intramural Purkinje network, rather than being a reflection of ventricular mass.
浦肯野纤维的电冲动传导速度比工作心肌细胞快得多。因此，浦肯野网络的分布对心室激动的时间和协调性至关重要。浦肯野纤维存在于所有哺乳动物种属的心内膜下，但一些哺乳动物还存在着心肌内浦肯野纤维网络，它可以实现整个心室壁的瞬间、爆发样激活，并在心电 II 导联中产生 rS 形态。
将马心脏的解剖结构和传导系统的分布和组织学与心室激动模式相关联，以解释马心脏独特电轴的机制。
通过组织化学方法确定心脏传导系统的形态和分布。使用 Einthoven 和正交配置测量心电图的电活动。
马心脏的长轴接近垂直。在结区外，传导系统由浦肯野纤维组成，通过连接蛋白 43 连接，并与长而细的平行运行的过渡细胞相连。浦肯野纤维网络深入心室壁。在正交配置中记录的心电图显示平均电轴指向颅侧向左，表明心室激动呈心尖到基底方向。
马心脏的平均电轴方向由心肌内浦肯野纤维网络的结构决定，而不是心室质量的反映。
