The heart is an electric and biochemical syncytium with its cardiac myocytes coupled by gap junctions that allow the passage of both ionic current and small molecules.¹ Electric coupling allows the rapid spread of depolarization through the atrium, ventricle, and specialized conduction system that is required for coordinated and efficient mechanical function. In addition, these low-resistance intercellular connections help to prevent arrhythmias in several ways. First, tight coupling leads to synchronization of repolarization across the cardiac chambers that decreases dispersion of repolarization and refractoriness and prevents functional reentry.² Second, the flow of ions and metabolites minimizes the differences at the single cell level that could result from variations in ion channel expression and metabolic state, stabilizing electric propagation and preventing triggered activity. Third, if an aberrant action potential is triggered in a cell or small group of cells, the source–sink mismatch of the electric syncytium will often prevent propagation. In fact, both theoretical and experimental studies have estimated the number of synchronized myocytes required to initiate a premature ventricular beat.^3,4

Article, see p 1379

Although coupling between cardiac myocytes is important, the absence of coupling is also critical in some circumstances. Electric isolation is required …

心脏是一种电气和生化合胞体，其心肌细胞通过间隙连接耦合，从而允许离子电流和小分子通过。¹电耦合可以使去极化迅速扩散到心房，心室和专用传导系统中，这是协调有效的机械功能所必需的。另外，这些低电阻的细胞间连接以多种方式有助于预防心律不齐。首先，紧密的耦合导致整个心腔内复极化的同步，从而减少了复极化和难治性的分散，并阻止了功能性折返。^2个其次，离子和代谢物的流动将单细胞水平上的差异减至最小，该差异可能是由于离子通道表达和代谢状态的变化而引起的，从而稳定了电传播并阻止了触发的活动。第三，如果在一个细胞或一小组细胞中触发了异常动作电位，则电合胞体的源-漏失配通常会阻止其传播。实际上，无论是理论研究还是实验研究，都已经估算出启动早搏性心室搏动所需的同步肌细胞的数量。^3，4

文章，请参阅第1379页

尽管心肌细胞之间的偶联很重要，但是在某些情况下缺乏偶联也很关键。需要电气隔离…