Toward an Integrated Understanding of the Purkinje Fibers in the Heart: The Functional and Morphological Interconnection between the Purkinje Fibers and Ventricular Muscle

Abstract

Purkinje fibers are an essential element of the conduction system that provides for coordinated ventricular contraction of the heart. Although classic studies established structure and electrical activities of Purkinje fibers, an integrated understanding of the Purkinje-ventricular interconnection within the working heart remains to be had. In this review article we will briefly overview the gross anatomy and cytological characteristics of Purkinje fibers and their transition to the ventricular muscle, and we will discuss functional and morphological aspects of the Purkinje-ventricular interconnection from the perspectives of electrophysiology, distribution of gap junctions, and intracellular Ca 2+ ([Ca 2+ ] i ) dynamics. Furthermore, the potential usefulness of the recently developed optical voltagemapping and in situ real-time confocal [Ca 2+ ] i imaging techniques is discussed as an integrated approach to the pathophysiological investigation of the Purkinje-ventricular interconnection in the heart.

Role of the Purkinje-Muscle Junction on the Ventricular Repolarization Heterogeneity in the Healthy and Ischemic Ovine Ventricular Myocardium

“…APD maxima remained localized to PMJs, in ischemic ( Figure 5 ) conditions with little change in APD compared to control. The preservation of PFs and their electrophysiological state during ischemic insult has previously been documented ( Tanaka et al, 2005 ; Ono et al, 2009 ). This phenomenon is thought to occur due to high glycogen levels permitting resistance to hypoxia.…”

“…Although the resistance of PF toward ischemic insults due to a high metabolic reserve is well known ( Tanaka et al, 2005 ; Ono et al, 2009 ), as well as its potential to trigger arrhythmias ( Haissaguerre et al, 2002a ), the role of repolarization heterogeneity at the PMJ in providing an arrhythmogenic substrate during ischemia remains to be elucidated.…”

Pacing-Induced Non-Uniform Ca²⁺ Dynamics in Rat Atria Revealed by Rapid-Scanning Confocal Microscopy

“…Given that cardiac performance is determined by electromechanical coordination of individual cardiomyocytes, visualization of the cellular aspects of intracellular Ca 2+ concentration ([Ca 2+ ] i ) dynamics in the heart is an important means of understanding cardiac pathophysiology [ 24 ]. So far, studies on [Ca 2+ ] i dynamics of cardiomyocytes have been well described not only under enzymatically isolated conditions [ 6 , 22 ] but also in working ventricles [ 1 , 9 – 13 , 18 , 20 , 23 – 25 ]. For example, we have reported cellular [Ca 2+ ] i dynamics in rat hearts imaged by using in situ rapid scanning confocal microscopy [ 9 – 12 , 23 – 25 ].…”

“…So far, studies on [Ca 2+ ] i dynamics of cardiomyocytes have been well described not only under enzymatically isolated conditions [ 6 , 22 ] but also in working ventricles [ 1 , 9 – 13 , 18 , 20 , 23 – 25 ]. For example, we have reported cellular [Ca 2+ ] i dynamics in rat hearts imaged by using in situ rapid scanning confocal microscopy [ 9 – 12 , 23 – 25 ]. These studies revealed that individual ventricular myocytes in the intact heart show spatiotemporally uniform [Ca 2+ ] i on beat-to-beat basis, whereas non-uniform [Ca 2+ ] i dynamics emerge in diseased or injured hearts, e.g., Ca 2+ waves that emerge under [Ca 2+ ] i overload.…”

Arrhythmogenic substrates in myocardial infarct

“…Purkinje fibers play essential roles in impulse propagation to the ventricular myocardium, and their impaired function can become arrhythmogenic 41,42 . Under simultaneous recording on electrocardiogram, spatiotemporal changes in fluo3 fluorescence intensity were visualized in subendocardial regions of the right ventricular septum 43,44 . Purkinje fibers were distinguished from ventricular myocytes by their morphology in fluo 3‐fluorescence and later staining with acetylthiocholine iodide.…”