Morphological variations of the conduction system in the atrioventricular zone and its clinical relationship in differen
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ORIGINAL ARTICLE
Morphological variations of the conduction system in the atrioventricular zone and its clinical relationship in different species Fabián Gómez‑Torres1,2 · Luis Ballesteros‑Acuña2 · Amparo Ruíz‑Sauri1,3 Received: 18 February 2020 / Accepted: 12 September 2020 © Japanese Association of Anatomists 2020
Abstract Atrioventricular node is responsible for delaying the passage of the electrical impulse to ventricles in order to protect them from fast depolarizations coming from the atria. The importance of this study is to identify the morphological variations of the components of atrioventricular zone that affect the conduction system and its clinical relationship in different spe‑ cies of mammals. We analyzed ten human hearts, nine from horses, eight from pigs, and five from dogs without a clinical history of cardiac pathologies. Histological section thickness of 5 μm were obtained with a microtome and stained with hematoxylin–eosin and Masson’s trichrome. We observed both an increase in collagen fibers and a decrease in the size of P cells (nodal pacemaker cells) within the atrioventricular node in dogs, horses and pigs in cases that presented cartilage in fibrous body. The percentage of fundamental substance in atrioventricular node was significantly higher in dogs and the percentage of collagen fibers was higher in pigs, both than in humans. The presence of cartilaginous metaplasia in cardiac fibrous skeleton from different species decreases the size of atrioventricular node and its cells and increases the percentage of collagen fibers within the node, which can reduce the transmission of the electrical impulse to ventricles and therefore predispose to the presentation of ventricular arrhythmias. Morphometric analysis has allowed us to objectively quantify each of the components of AV node and compare them in the different species. Keywords Arrhythmia · Atrioventricular node · Cartilage · Fibrous body · P cell Abbreviations CCS Cardiac conduction system AV Atrioventricular AVF Atrioventricular fascicle CFS Cardiac fibrous skeleton
* Amparo Ruíz‑Sauri Amparo.Ruiz‑[email protected] 1
Department of Pathology, Faculty of Medicine, 1st floor, Universitat de Valencia, Av. de Blasco Ibáñez, 15, 46010 Valencia, Spain
2
Department of Basic Sciences, School of Medicine, Universidad Industrial de Santander, Cra 32 # 29–31, 68002 Bucaramanga, Colombia
3
INCLIVA Biomedical Research Institute, Av. de Blasco Ibáñez, 17, 46010 Valencia, Spain
Introduction The importance of cardiac conduction system (CCS) in atrioventricular zone is that atrioventricular (AV) node is responsible for delaying the passage of electrical impulse to ventricles to protect them from fast depolarizations coming from the atria under normal conditions or, even, when there are atrial ectopic foci due to supraventricular arrhythmias. Different morphological variations at atrioventricular level due to factors such as aging have been reported in humans: cardiac block due to calcareous lesions in atrio‑ ventricular fascicle (AVF) (
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