Histological and morphometric study of the components of the sinus and atrioventricular nodes in horses and dogs

Gómez-Torres, Fabián; Ballesteros-Acuña, Luis Ernesto; Ruiz‐Saurí, Amparo

doi:10.1016/j.rvsc.2019.08.001

Cited by 6 publications

(12 citation statements)

References 24 publications

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“…The results of pathological studies not only supported the prevalence of severe coronary atherosclerosis in SCD but also indicated that 10%-50% of victims suffered an asymptomatic acute myocardial infarction (AMI) [4] and a higher percentage suffered subclinical early myocardial ischemia [5]. Similar findings obtained in other species can be attributed to the similarities in cardiac function between humans and these species, especially dogs [6]. The sinoatrial node (SAN) initiates the cardiac electrical impulse, which controls the coordinated rhythmic contractions of the mammalian heart [7][8][9][10][11].…”

Section: Introductionsupporting

confidence: 60%

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Histopathological changes in the electrical conduction of cardiac nodes after acute myocardial infarction in dogs and horses, compared with findings in humans: A histological, morphometrical, and immunohistochemical study

Gómez-Torres,

Ballesteros-Acuña,

Ruíz-Sauri

2023

Vet World

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Background and Aim: The heart conduction system is responsible for the occurrence of various types of cardiac arrhythmia. This study aimed to histologically and morphometrically describe damaged cardiac nodes during acute myocardial infarction and to compare them with normal tissues in dogs and horses. Materials and Methods: This study describes the morphometry of cardiac nodes in five dogs and five elderly horses that succumbed to sudden cardiac death (SCD). A computerized morphometric study was conducted to determine the number of cells composing the nodes, different shape and size parameters of nodes, and their relationship with degenerative changes due to cardiac conditions. Results: In both species, the sinoatrial node (SAN) was ovoid in shape whereas the atrioventricular node (AVN) was pyramidal in shape. The percentage of collagen fibers inside the SAN of dogs (47%) and horses (50%) was found to be higher than that of cells. In contrast, the percentage of cells in the AVN of dogs (24%) and horses (16%) was higher than that of connective tissues. In the SAN, the area (p = 0.09), maximum diameter (<0.001), and mean diameter (0.003) of P cells were larger in dogs than in horses. Conclusion: Overall, the SAN cells and surrounding cardiomyocytes in dogs and horses as well as the AVN cells in dogs that succumbed to SCD decreased in size compared with those in normal hearts. Keywords: atrioventricular node, dog, horse, myocardial infarction, sinoatrial node.

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Section: Introductionsupporting

confidence: 60%

“…A thin capsule of connective tissue was found surrounding the node in all horses. The different morphometric parameters measured for the SAN of both species are presented in Table-1 [6].…”

Section: Sinoatrial Nodementioning

confidence: 99%

Histopathological changes in the electrical conduction of cardiac nodes after acute myocardial infarction in dogs and horses, compared with findings in humans: A histological, morphometrical, and immunohistochemical study

Gómez-Torres,

Ballesteros-Acuña,

Ruíz-Sauri

2023

Vet World

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“…An overview of a transverse section of the SAN is shown in Figure 3A. The SAN was visible as a pale triangular streak assumed to reflect the connective tissue and situated immediately beneath the epicardium of the sulcus terminalis as previously described in horses 26–28 . Working atrial cardiomyocytes were found beneath the SAN.…”

Section: Resultsmentioning

confidence: 65%

“…The SAN was visible as a pale triangular streak assumed to reflect the connective tissue and situated immediately beneath the epicardium of the sulcus terminalis as previously described in horses. [26][27][28] Working atrial cardiomyocytes were found beneath the SAN. The branches of the central SAN artery were surrounded by several nerves of variable size.…”

Section: The Sinoatrial Node and Atriamentioning

confidence: 99%

Intramural Purkinje fibers facilitate rapid ventricular activation in the equine heart

et al. 2023

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Background 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. Aim 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. Methods 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. Results 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. Conclusion 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.

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“…However, all of these cases presented without detailed information of the histology. Other studies reporting on the histologic characteristics of the AV node in healthy horses exist, in which some mention the presence of cardiac cartilage or even a cardiac bone [ 28 , 29 , 30 , 31 ]. The aortic root lies in the continuation of the central fibrous body, which in many mammals is transformed into cartilage and referred to as the cardiac cartilage [ 31 ].…”

Section: Discussionmentioning

confidence: 99%

Cartilaginous Intrusion of the Atrioventricular Node in a Quarter Horse with a High Burden of Second-Degree AV Block and Collapse: A Case Report

Nissen

Saljic

Kjeldsen

et al. 2022

Animals

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Second-degree atrioventricular (AV) block is the most common cardiac arrhythmia in horses, affecting 40–90% depending on breed. Usually, the AV blocks occur while the horses are resting and disappear upon exercise and are, therefore, considered to be uneventful for horses. However, if the AV blocks occur frequently, this may result in syncope and collapse. Identifying the cause of second-degree AV block is difficult and often subscribed to high vagal tone. In this report, we present an eight-year-old Quarter horse with a high burden of second-degree AV blocks and multiple collapses. The clinical examination, including neurological examination, blood analysis, 24-h ECG recording and cardiac echocardiography, did not reveal any signs of general or cardiovascular disease besides a high burden of second-degree AV blocks (~300 blocks per hour) and a hyperechoic area in the AV nodal region. An implantable loop recorder (ILR) was inserted to monitor the cardiac rhythm. The ILR detected several consecutive second-degree AV blocks and pauses above 5 s. However, unfortunately, no recordings were available during the collapses. Eventually, the horse was euthanized and the heart inspected. The aortic root was severely cartilaginous and appeared to penetrate the AV node, especially in the His bundle region, possibly explaining the hampered AV conduction. Nevertheless, it is still uncertain if the AV nodal disruption caused the collapses and more knowledge on AV nodal diseases in horses is warranted.

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Histological and morphometric study of the components of the sinus and atrioventricular nodes in horses and dogs

Cited by 6 publications

References 24 publications

Histopathological changes in the electrical conduction of cardiac nodes after acute myocardial infarction in dogs and horses, compared with findings in humans: A histological, morphometrical, and immunohistochemical study

Histopathological changes in the electrical conduction of cardiac nodes after acute myocardial infarction in dogs and horses, compared with findings in humans: A histological, morphometrical, and immunohistochemical study

Intramural Purkinje fibers facilitate rapid ventricular activation in the equine heart

Cartilaginous Intrusion of the Atrioventricular Node in a Quarter Horse with a High Burden of Second-Degree AV Block and Collapse: A Case Report

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