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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.

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SUMMARY: Diabetic cardiomyopathy, characterized by diabetes mellitus (DM) -induced cardiac muscular abnormalities, is a strong inducer of impaired cardiac contraction and arrhythmia. Atrioventricular block, a serious type of arrhythmia resulting from interruption of cardiac impulse conduction via the atrioventricular node (AVN), frequently occurs among diabetic patients. However, details of structural changes in AVN in DM remain poorly explained. Here, this study defined the effects of DM on the morphological remodeling of the AVN in male Sprague Dawley rats induced by intraperitoneal injection of streptozotocin (60 mg/kg body weight). At 24 weeks, the pathological changes in the AVN were assessed by light microscopy (LM) and transmission electron microscopy (TEM). Under LM, the AVN in diabetic rats became a less compact mass and exhibited the intracellular vacuolation. The nodal cells were more varied in sizes with the absence or shrinkage of nuclei and clear cytoplasm compared to the control. The collagen content significantly increased in relation to the presence of myofibroblasts. Consistent with LM, TEM images of the diabetic nodal cells revealed several signs of cell damage, such as mitochondrial changes, deterioration of cell organelles, gap junction internalization, and cell separation. Furthermore, changes in AVN innervation, evidenced by damaged Schwann cells and axons, were also found. These results indicated alterations in important components in the AVN during diabetic condition, which may lead to the impairment of electrical conduction, causing abnormal cardiac functions in diabetic patients.

La miocardiopatía diabética, caracterizada por anomalías musculares cardíacas inducidas por diabetes mellitus (DM), es un fuerte inductor de alteración de la contracción cardíaca y arritmia. El bloqueo atrioventricular, un tipo grave de arritmia resultante de la interrupción de la conducción del impulso cardíaco a través del nodo atrioventricular (NAV), se produce con frecuencia entre los pacientes diabéticos. Sin embargo, los detalles de los cambios estructurales en NAV en DM siguen estando pobremente explicados. Aquí, este estudio definió los efectos de la DM en la remodelación morfológica del NAV en ratas macho Sprague Dawley inducidas por inyección intraperitoneal de estreptozotocina (60 mg/kg de peso corporal). A las 24 semanas, los cambios patológicos en el NAV se evaluaron mediante microscopía óptica (MO) y microscopía electrónica de transmisión (MET). Bajo MO, el NAV en ratas diabéticas se convirtió en una masa menos compacta y exhibió la vacuolización intracelular. Las células nodales tenían tamaños más variados con ausencia o contracción de núcleos y citoplasma claro en comparación con el control. El contenido de colágeno aumentó significativamente en relación con la presencia de miofibroblastos. De acuerdo con MO, las imágenes MET de las células nodales diabéticas revelaron varios signos de daño celular, como cambios mitocondriales, deterioro de los orgánulos celulares, internalización de uniones comunicantes y separación celular. Además, también se encontraron cambios en la inervación del NAV, evidenciados por schwannocitos y axones dañados. Estos resultados indicaron alteraciones en componentes importantes en el NAV durante la condición diabética, lo que puede conducir al deterioro de la conducción eléctrica, causando funciones cardíacas anormales en estos pacientes.

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Two groups of investigators investigated the heart pacemaker and its morphological basis in the early twentieth century. The first group was formed by Henrich Ewald Hering (physiologist), Sunao Tawara and Ludwig Aschoff (morphologists). The second group was composed of James Mackenzie (general practitioner and clinical investigator), Arthur Keith and Martin Flack (morphologists). These groups were formed almost at the same time in 1903. Their work resulted in the discovery of the atrioventricular node and Purkinje network (Sunao Tawara, in 1906), heart pacemaker (H E Hering, in 1907) and sinoatrial node (Keith and Flack, in 1907). Here, it is shown how the interconnections of the concurrent works of these groups resulted in the discovery not only of the function, but also of the structure of the sinoatrial node.

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The name Ivan Mahaim is well-known to electrophysiologists. However, alternative anatomical substrates can produce the abnormal rhythms initially interpreted on the basis of the pathways he first described. These facts have prompted suggestions that Mahaim should be deprived of his eponym. It is agreed that specificity is required when describing the pathways that produce the disordered cardiac conduction, and that the identified pathways should now be described in an attitudinally appropriate fashion. The authors remain to be convinced that understanding will be enhanced simply by discarding the term 'Mahaim physiology' from the lexicon. It is fascinating to look back at the history of accessory atrioventricular junctional conduction pathways outside the normal accessory atrioventricular conduction system, and their possible role in rhythm disturbances. It took both the anatomist and the clinical arrhythmologist quite some time to understand the complex anatomical architecture and the ensuing electrophysiological properties. Over the years, the name Mahaim was often mentioned in those discussions, although these pathways were not the ones that produced the eponym. The reason for this review, therefore, is to present relevant information about the person and what followed thereafter.

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Atrioventricular blocks are chronotropic abnormalities produced by multifactorial alterations in the cardiac innervation system, specifically between the internodal pathways between the sinus node and the atrioventricular node. These bradyarrhythmias represent 2.3% of cardiac alterations in intrauterine life, registering one case for every 20 000 to 25 000 live births. However, its occurrence in childhood and adolescence is unknown. Likewise, the percentage of idiopathic atrioventricular blocks in this group in Colombia is unknown to date. Among the possible etiol-ogies, congenital and acquired causes have been documented. Some examples are isolated cases found in pregnancies with maternal isoimmunization, from carriers with lupus, and in coexis-tence with structural alterations, such as anomalies of the interventricular septum due to cardiac tumors and defects in the ostium and septation of the cardiac chambers. Atrioventricular blocks are also associated with respiratory syncytial virus infection and concomitant viral myocarditis and with cardiomyopathies of immune, rheumatic, infectious, tumoral, and structural origin, in addition to mitochondrial diseases such as Kearns Sayre syndrome, presenting with multi- organ involvement. These etiologies lead to chronic inflammation with fibrotic repair in the cardiac conduction system, which alters the transmission of the action potential and bradycardia with atrioventricular asynchrony. Idiopathic causes described in the onset of primary dysautonomia have also been reported. We present the case of an 11- year- old patient with a headache crisis and paroxysmal vegetative symptoms associated with repeated fainting, with subsequent studies where no structural alterations or autoimmune findings were identified. The patient was diag-nosed with idiopathic complete atrioventricular block and received expectant management by the electrophysiology service.

Los bloqueos auriculoventriculares son aberraciones cronotrópicas producidas por alteraciones de índole multifactorial en el sistema de inervación cardíaco. Específicamente se localizan entre las vías internodales que conducen el potencial de acción desde el nodo sinusal hasta el nodo auriculoventricular. Estos representan el 2,3% de las alteraciones cardíacas en la vida intrauterina, registrándose un caso por cada 20 000 a 25 000 nacidos vivos. Sin embargo, su ocurrencia en la infancia temprana y la edad escolar es desconocida. Asimismo, el porcentaje de causas idiopáticas de bloqueos auriculoventriculares en esta etapa de la vida es desconocido hasta el momento en Colombia. Dentro de las posibles etiologías se han documentado causas congénitas y adquiridas. Algunos ejemplos son casos aislados producto de isoinmunización materna, en hijo de madre lúpica o en coexistencia con alteraciones estructurales como anomalías del septo interventricular de índole neoplásico, defectos relacionados al ostium y la tabicación de las cámaras cardíacas. También se han descrito casos secundarios a infección por virus sincitial respiratorio y miocarditis vírica concomitante, incluyendo cardiomiopatías de origen inmune, reumático, infeccioso, tumoral, estructural, además de aquellas con compromiso mitocondrial en el cardiomiocito (síndrome de Kearns Sayre) con presentación más tardía con afectación multiorgánica. Todas ellas destacan por un fenómeno en común a nivel celular, referente a la inflamación crónica con reparación fibrótica en el sistema de conducción cardíaco, que conlleva alteraciones de la transmisión del potencial de acción y bradicardia con asíncrona auriculoventricular. También se han reportado causas idiopáticas descritas en el debut de una disautonomía primaria. Se presenta el caso de una paciente de 11 años con crisis de cefalea y síntomas vegetativos paroxísticos asociados a lipotimias a repetición, con posteriores estudios de extensión sin identificación de alteraciones estructurales ni hallazgos autoinmunes. A la niña se le diagnosticó bloqueo auriculoventricular completo, idiopático por lo que recibió manejo expectante por parte del servicio de electrofisiología.

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Los bloqueos auriculoventriculares son aberraciones cronotrópicas producidas por alteraciones de índole multifactorial en el sistema de inervación cardíaco. Específicamente se localizan entre las vías internodales que conducen el potencial de acción desde el nodo sinusal hasta el nodo auriculoventricular. Estos representan el 2,3% de las alteraciones cardíacas en la vida intrauterina, registrándose un caso por cada 20 000 a 25 000 nacidos vivos. Sin embargo, su ocurrencia en la infancia temprana y la edad escolar es desconocida. Asimismo, el porcentaje de causas idiopáticas de bloqueos auriculoventriculares en esta etapa de la vida es desconocido hasta el momento en Colombia. Dentro de las posibles etiologías se han documentado causas congénitas y adquiridas. Algunos ejemplos son casos aislados producto de isoinmunización materna, en hijo de madre lúpica o en coexistencia con alteraciones estructurales como anomalías del septo interventricular de índole neoplásico, defectos relacionados al ostium y la tabicación de las cámaras cardíacas. También se han descrito casos secundarios a infección por virus sincitial respiratorio y miocarditis vírica concomitante, incluyendo cardiomiopatías de origen inmune, reumático, infeccioso, tumoral, estructural, además de aquellas con compromiso mitocondrial en el cardiomiocito (síndrome de Kearns Sayre) con presentación más tardía con afectación multiorgánica. Todas ellas destacan por un fenómeno en común a nivel celular, referente a la inflamación crónica con reparación fibrótica en el sistema de conducción cardíaco, que conlleva alteraciones de la transmisión del potencial de acción y bradicardia con asíncrona auriculoventricular. También se han reportado causas idiopáticas descritas en el debut de una disautonomía primaria. Se presenta el caso de una paciente de 11 años con crisis de cefalea y síntomas vegetativos paroxísticos asociados a lipotimias a repetición, con posteriores estudios de extensión sin identificación de alteraciones estructurales ni hallazgos autoinmunes. A la niña se le diagnosticó bloqueo auriculoventricular completo, idiopático por lo que recibió manejo expectante por parte del servicio de electrofisiología.

Atrioventricular blocks are chronotropic abnormalities produced by multifactorial alterations in the cardiac innervation system, specifically between the internodal pathways between the sinus node and the atrioventricular node. These bradyarrhythmias represent 2.3% of cardiac alterations in intrauterine life, registering one case for every 20 000 to 25 000 live births. However, its occurrence in childhood and adolescence is unknown. Likewise, the percentage of idiopathic atrioventricular blocks in this group in Colombia is unknown to date. Among the possible etiol-ogies, congenital and acquired causes have been documented. Some examples are isolated cases found in pregnancies with maternal isoimmunization, from carriers with lupus, and in coexis-tence with structural alterations, such as anomalies of the interventricular septum due to cardiac tumors and defects in the ostium and septation of the cardiac chambers. Atrioventricular blocks are also associated with respiratory syncytial virus infection and concomitant viral myocarditis and with cardiomyopathies of immune, rheumatic, infectious, tumoral, and structural origin, in addition to mitochondrial diseases such as Kearns Sayre syndrome, presenting with multi- organ involvement. These etiologies lead to chronic inflammation with fibrotic repair in the cardiac conduction system, which alters the transmission of the action potential and bradycardia with atrioventricular asynchrony. Idiopathic causes described in the onset of primary dysautonomia have also been reported. We present the case of an 11- year- old patient with a headache crisis and paroxysmal vegetative symptoms associated with repeated fainting, with subsequent studies where no structural alterations or autoimmune findings were identified. The patient was diag-nosed with idiopathic complete atrioventricular block and received expectant management by the electrophysiology service.

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Abstract Background: Current pacemakers allow for the continuous recording of the occurrence of arrhythmic events. One of the most frequent arrhythmias after implantation of a device is atrial fibrillation (AF), an important risk factor for embolic events. The frequency of this arrhythmia in pacemaker patients has not been widely studied. Objectives: This study aimed to evaluate the prevalence, incidence, and predictors of the occurrence of AF in patients with double-chamber pacemakers and without a history of atrial fibrillation prior to implantation. Methods: A dynamic, retrospective, and prospective cohort study was carried out with 186 patients undergoing biannual follow-up of the double-chamber pacemaker, without previous AF, in a single service, between 2016 and 2018. Clinical data were collected from the medical records and the telemetry of the device and the prevalence, incidence rate, relative risk by univariate analysis (by chi-square), and risk ratio were calculated by multivariate analysis (by Cox regression); values of p<0.05 were considered significant. Results: There was a prevalence of 25.3% FA, with an incidence of 5.64 cases / 100 persons-year. The median time for the development of arrhythmia was 27.5 months. Multivariate analysis identified 5 statistically significant predictors: male gender, OR: 2.54 [1.04-6.15]; coronary artery disease, OR: 2.98 [1.20-7.41]; hypothyroidism, OR: 3.63 [1.46-9.07]; prior heart surgery, OR: 2.67 [1.01-7]; and left atrial enlargement, OR: 2.72 [1.25-5.92]. Conclusions: The prevalence and incidence of AF in this population are high. Risk factors for AF were: male gender, coronary artery disease, hypothyroidism, prior heart surgery, and left atrial enlargement.

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Abstract New translational concepts on cellular and tissue substrate of cardiac arrhythmias have been responsible for the development of non-pharmacological interventions, with important achievements compared to the conventional approach with antiarrhythmic drugs. In addition, the increasing knowledge of anatomical and electrophysiological studies, sophisticated mapping methods, special catheters, and controlled clinical trials have favored the progression of ablation of tachyarrhythmias, particularly of ventricular tachyarrhythmias and atrial fibrillation.

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Sunao Tawara, who was born in 1873 and died in 1952, is considered the father of modern cardiac electrophysiology. He published his monumental monograph describing the atrioventricular conduction axis in 1906. He achieved this task in the face of multiple tribulations as a doctoral student working in a cultural environment that was not his own. Although his letters underscoring the publication of the monograph have been published, little emphasis has been placed on the potential problems he encountered in bringing his task to fruition. For example, it was not until the final 6 months of his studies that he resolved the issue of the connection between the atrioventricular bundle and the so called "Purkinje cardiomyocytes". His exchanges with his mentor, Ludwig Aschoff, emphasized that the difficulties he encountered in making the connection caused him quite some turmoil. We believe that this issue, and others that he identified in his correspondence, are worthy of further attention.

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It was Sunao Tawara who, in 1906, established the foundations for knowledge of the arrangement of the atrioventricular conduction axis in man and other mammals. Study of the hearts of ungulates was a central part in his investigation, which assessed other species, including man. He described several subtle differences between the mammals. We have now ourselves studied the cardiac conduction tissue of the ox heart, comparing our findings with our knowledge of the arrangement in man, and providing new insights into the differences illustrated by Tawara. It is, perhaps, surprising that these differences, although subtle, have not attracted more attention. We show that the major difference is the fact that the noncoronary aortic sinus in the ox heart is mainly supported by the myocardium of the ventricular septum, whereas in the human heart the sinus, and its leaflet, are in fibrous contiguity with the aortic leaflet of the mitral valve. It is this feature that determines the difference in the arrangement of the conduction axis between the species. We also show that the emergence of the left bundle branch on the left ventricular aspect of the muscular septum is more variable than previously described. Clin. Anat. 33:383-393, 2020. © 2019 Wiley Periodicals, Inc.

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A dexmedetomidina é um fármaco agonista a-2 adrenérgico utilizado na anestesiologia veterinária, devido a suas propriedades sedativas e analgésicas. Existem preocupações quanto aos seus efeitos colaterais, principalmente cardiovasculares, dentre eles arritmias. As quais podem comprometer o débito cardíaco e a perfusão tecidual. As arritmias que podem ser observadas com o uso da dexmedetomidina são: bloqueio átrio ventricular de 1º, 2º e 3º grau; arritmia sinusal, e pausa sinusal. Dentre elas a de maior ocorrência é o bloqueio atrioventricular, principalmente o de 2º grau. Essas alterações são dose-dependentes, estudos demonstram que doses de 1 µg /kg podem desencadear a ocorrência de bradiarritmias. O tratamento das arritmias atrioventriculares envolve a administração de anticolinérgicos, antiarrítmicos e no caso de alterações desencadeadas pelo uso da dexmedetomidina a aplicação de um antagonista a-2 adrenérgico. Esta revisão tem como objetivo discorrer sobre as arritmias em cães ocasionadas pelo uso da dexmedetomidina.

Dexmedetomidine is a α-2 adrenergic agonist drug used in veterinary anesthesiologydue to its sedative and analgesic properties. There are concerns about its side effects, especially cardiovascular, among them arrhythmias. These may compromise cardiac output and tissue perfusion. The arrhythmias that may be observed with the use of dexmedetomidine are: ventricularatrium blockade of 1st, 2nd and 3rd degree; sinus arrhythmia, and sinus pause. Among them, the most frequent occurrence is atrioventricular block, especially the second degree. These changes are dose-dependent, studies have shown that doses of 1 μg/kg can trigger the occurrence of bradyarrhythmias. Treatment of atrioventricular arrhythmias involves the administration of anticholinergics, antiarrhythmics and in the case of changes triggered by the use of dexmedetomidinethe application of a α-2 adrenergic antagonist. This review aims to discuss the arrhythmias in dogs caused by the use of dexmedetomidine.

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A dexmedetomidina é um fármaco agonista a-2 adrenérgico utilizado na anestesiologia veterinária, devido a suas propriedades sedativas e analgésicas. Existem preocupações quanto aos seus efeitos colaterais, principalmente cardiovasculares, dentre eles arritmias. As quais podem comprometer o débito cardíaco e a perfusão tecidual. As arritmias que podem ser observadas com o uso da dexmedetomidina são: bloqueio átrio ventricular de 1º, 2º e 3º grau; arritmia sinusal, e pausa sinusal. Dentre elas a de maior ocorrência é o bloqueio atrioventricular, principalmente o de 2º grau. Essas alterações são dose-dependentes, estudos demonstram que doses de 1 µg /kg podem desencadear a ocorrência de bradiarritmias. O tratamento das arritmias atrioventriculares envolve a administração de anticolinérgicos, antiarrítmicos e no caso de alterações desencadeadas pelo uso da dexmedetomidina a aplicação de um antagonista a-2 adrenérgico. Esta revisão tem como objetivo discorrer sobre as arritmias em cães ocasionadas pelo uso da dexmedetomidina.(AU)

Dexmedetomidine is a α-2 adrenergic agonist drug used in veterinary anesthesiologydue to its sedative and analgesic properties. There are concerns about its side effects, especially cardiovascular, among them arrhythmias. These may compromise cardiac output and tissue perfusion. The arrhythmias that may be observed with the use of dexmedetomidine are: ventricularatrium blockade of 1st, 2nd and 3rd degree; sinus arrhythmia, and sinus pause. Among them, the most frequent occurrence is atrioventricular block, especially the second degree. These changes are dose-dependent, studies have shown that doses of 1 μg/kg can trigger the occurrence of bradyarrhythmias. Treatment of atrioventricular arrhythmias involves the administration of anticholinergics, antiarrhythmics and in the case of changes triggered by the use of dexmedetomidinethe application of a α-2 adrenergic antagonist. This review aims to discuss the arrhythmias in dogs caused by the use of dexmedetomidine.(AU)

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El uso de la radioterapia ha contribuido a mejorar la supervivencia de pacientes con diversos tumores malignos relacionados con la región torácica. No obstante, la irradiación cardíaca a una dosis suficientemente alta puede dañar prácticamente cualquier componente del mismo, incluyendo el sistema de conducción. Se describe el caso de un paciente que desarrolló bloqueo auriculoventricular completo, más de veinte años después de recibir radioterapia supradiafragmática para el tratamiento de un linfoma de Hodgkin.

The use of radiotherapy has contributed to improving the survival in patients with diverse malignancies related to the thoracic region. Nevertheless, cardiac radiation in sufficiently high dose can damage virtually any of its components, including the conduction system. We describe the case of a patient who developed a complete atrioventricular block more than twenty years after receiving supradiaphragmatic radiotherapy for Hodgkin lymphoma.

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Background: The components of the cardiac conduction system (CCS) were discovered almost two centuries and presentedin the diagrammatic forms. This should be due to the diffi culty in distinguishing the CCS from the surrounding cardiactissues and the lack of information concerning the precise landmarks for gross dissection. Furthermore the CCS in pig,the animal regarded as a suitable model for the assessment of catheter based intervention, has not been reported. The aimsof the present study were to demonstrate the gross anatomic architecture of CCS in the swine heart, and to provide thevaluable landmarks for the gross anatomic dissection of the CCS.Materials, Methods & Results: Twenty hearts of adult Large White pigs (Sus Scrofa domesticus) were used. Fifteen heartswere elucidated by gross anatomic dissection. The tissue blocks of the sinoatrial node (SAN) and atrioventricular conduction tissue of the fi ve hearts were prepared for histological investigation by staining with Masson’s trichrome. It was foundhistologically that the cardiac conduction tissues were clearly distinguishable from the surrounding cardiac myocardiumand connective tissue. Moreover, the histological information also navigated the location and anatomical architecture ofthe CCS which provided essential guideline for gross dissection. The SAN was somewhat spindle in shape which embedded in epicardial connective tissue of the terminal sulcus. In some cases, it was quite diffi cult to identifythe SAN, so thesinoatrial node artery was used as a clue. The AVN was an elliptical shaped which situated in subendocardial tissue atapex of the triangle of Koch on the atrial surface of the central fi brous body. The distal extremity of the AVN extended intothe central fi brous body to form the penetrating bundle of His. At the boundary between the membranous and muscularparts of the interventricular septum, the AV bundle of His divided into the right...

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Background: The components of the cardiac conduction system (CCS) were discovered almost two centuries and presentedin the diagrammatic forms. This should be due to the diffi culty in distinguishing the CCS from the surrounding cardiactissues and the lack of information concerning the precise landmarks for gross dissection. Furthermore the CCS in pig,the animal regarded as a suitable model for the assessment of catheter based intervention, has not been reported. The aimsof the present study were to demonstrate the gross anatomic architecture of CCS in the swine heart, and to provide thevaluable landmarks for the gross anatomic dissection of the CCS.Materials, Methods & Results: Twenty hearts of adult Large White pigs (Sus Scrofa domesticus) were used. Fifteen heartswere elucidated by gross anatomic dissection. The tissue blocks of the sinoatrial node (SAN) and atrioventricular conduction tissue of the fi ve hearts were prepared for histological investigation by staining with Massons trichrome. It was foundhistologically that the cardiac conduction tissues were clearly distinguishable from the surrounding cardiac myocardiumand connective tissue. Moreover, the histological information also navigated the location and anatomical architecture ofthe CCS which provided essential guideline for gross dissection. The SAN was somewhat spindle in shape which embedded in epicardial connective tissue of the terminal sulcus. In some cases, it was quite diffi cult to identifythe SAN, so thesinoatrial node artery was used as a clue. The AVN was an elliptical shaped which situated in subendocardial tissue atapex of the triangle of Koch on the atrial surface of the central fi brous body. The distal extremity of the AVN extended intothe central fi brous body to form the penetrating bundle of His. At the boundary between the membranous and muscularparts of the interventricular septum, the AV bundle of His divided into the right...(AU)

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The mechanisms of production, and gross, microscopic and electrocardiograhic findings of surgically-induced complete heart block (CHB) in the adult rat are presented. This is an effective in vivo model for establishing alternative methods to electronic pacemakers and for providing detailed information aimed at replacement, reduction and refinement of the technique. Sternal thoracotomy was employed to identify the epicardial fat pad by the aortic root, used as a landmark for cauterization of the atrioventricular (AV) node. Stable CHB was produced in 60 rats with a 70% survival rate. The best survival rate was observed in 8-week-old animals weighing 221 ± 27.6 g. Heart rate before cauterization was 387 ± 55 bpm, reduced after cauterization to 126 ± 40 bpm in the survival and to 65 ± 19 bpm in the non-survival groups. At 30 days findings were: elevated left ventricular end-diastolic pressure (21 ± 5.4 mmHg, P < 0.05); maximal rate of rise of left ventricular pressure (LVP) during isovolumetric contraction (2192 ± 235 mmHg/s, P < 0.05); maximal rate of decrease of LVP (-1658 ± 191 mmHg/s, P < 0.05); isovolumetric relaxation constant (5.7 ± 0.8 ms, P < 0.05) with wet-to-dry lung-weight ratio (78.1 ± 0.4, P < 0.05); heart weight/body weight (0.6 ± 0.1, P < 0.05); heart volume (1.8 ± 0.3 mL, P < 0.05); longitudinal diameter (20.2 ± 1.91 mm, P < 0.05); and transversal diameter (17.0 ± 1.4 mm, P < 0.05) with supported dilated cardiomyopathy which culminated in chronic heart failure. CHB hearts had increased preload and replacement of myofibrils by collagen. CHB was achieved reproducibly by cauterization of the rat AV node and/or His bundle. This led to electrophysiological, hemodynamic, and structural remodeling, and could be useful in long-term cardiac remodeling assessments and potential therapy development.

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BACKGROUND: It is necessary knowing the large variability of right coronary (RCA) artery specialty for its implications in surgical procedures and clinic events. This variability is usually related to the length, branches quantity, origin and irrigated territories. OBJECTIVE: To evaluate by direct examination the morphologic expression of RCA in Colombian people. METHODS: RCA were measured in 221 fresh hearts by RCA ostium canalization with polyester synthetic resin that was injected in their branches. RESULTS: The caliber of the RCA proximal segment and at the level of the acute angle of the heart was 3.42 ± 0.66 mm and 2.9 ± 0.50 mm, respectively. It ended between crux cordis and the left margin in 75.6 percent of specimens. Posterior interventricular artery (PIA) reached the inferior third, or the apex, or the anterior interventricular sulcus in 149 (67.4 percent) cases. Sinoatrial node artery (SNA) originated in the right coronary in 134 (60.6 percent) cases, 77 (34.9 percent) from circumflex artery (CxA) and from both in 10 (4.5 percent). Posterior right diagonal artery (PRDA) was noted in 38 (17.2 percent) hearts, but only 6 percent of the sample with long PIA, concomitantly presented the PRDA (P = 0.001). In right dominance SNA were originated from RCA in 54.7 percent and form CxA in 46.3 percent (P = 0.06). CONCLUSIONS: Caliber of the RCA and its branches is lesser than the majority of previous studies, while the PRDA frequency is slightly higher than the reported in literature. Clinical and pathological scenarios by these variations should be taken into account: hemodynamic procedures, cardiac surgery and arrhythmias from coronary occlusive disease.

INTRODUÇÃO: É necessário conhecer a grande variabilidade da artéria coronária direita (ACD), especialmente por suas implicações nos procedimentos cirúrgicos e eventos clínicos. Esta variabilidade está geralmente relacionada à extensão, à quantidade de ramos, à origem e aos territórios irrigados. OBJETIVO: Avaliar por exame direto a expressão morfológica da ACD em sujeitos colombianos. Métodos: As ACD foram medidas em 221 corações frescos pela canalização do óstio da ACD com uma resina de poliéster sintético que foi injetada em seus ramos. RESULTADOS: O calibre do segmento proximal da ACD e ao nível do ângulo agudo do coração foi de 3,42 ± 0,66 mm e 2,9 ± 0,50 mm, respectivamente. A ACD terminou entre a crux cordis e a margem esquerda em 75,6 por cento da amostra. A artéria interventricular posterior (AIP) atingiu o terço inferior, o ápice ou o sulco interventricular anterior em 149 (67,4 por cento) casos. A artéria do nó sinoatrial (ANS) surgiu da artéria coronária direita em 134 (60,6 por cento) casos, 77 (34,9 por cento) da artéria circunflexa (ACx) e de ambas em 10 (4,5 por cento) amostras. A artéria diagonal posterior direita (ADPD) foi observada em 38 (17,2 por cento) corações, mas apenas 6 por cento da amostra com uma AIP longa, apresentaram a ADPD (P=0,001). Em corações com dominância direita, a ANS surgiu da ACD em 54,7 por cento e da ACx em 46,3 por cento dos casos (P=0,06). CONCLUSÕES: O calibre da ACD e seus ramos é menor do que o relatado na maioria de estudos anteriores, enquanto que a frequência da ADPD é ligeiramente superior ao relatado na literatura. Cenários clínicos e patológicos por estas variações devem ser levados em conta: procedimentos de hemodinâmica, cirurgia cardíaca e arritmias de doença coronária obstrutiva.

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La expresión morfológica de las arterias nodales es relevante en el diagnóstico y manejo de eventos clínicos y en abordajes quirúrgicos del corazón. Se estudiaron 88 arterias nodales de corazones obtenidos como material de autopsia. Las arterias coronarias se inyectaron con resina poliéster pigmentada de color rojo. Se registraron las formas de presentación de las arterias nodales y sus características morfométricas. La arteria del nodo sinoatrial se originó de la coronaria derecha en 52 casos (59,1 porcentaje), de la circunfleja en 33 corazones (37,35 porcentaje) y de ambas en 3 (3,4 porcentaje). Su calibre proximal fue de 1,31 mm (más o menos 0,3), correspondiente a las arterias originadas de la coronaria derecha de 1,25 mm (más o menos 0,3) mientras que las que se originaron de la arteria circunfleja obtuvieron un calibre de 1,42 mm (más o menos 0,3), siendo esta diferencia significativa (p= 0,01). Se originó con mayor frecuencia en el tercio anteromedial, tanto de la coronaria derecha como de la circunfleja (54,6 porcentaje y 61,2 porcentaje respectivamente). En su segmento final cruzó por delante de la desembocadura de la vena cava superior en la mayoría de los casos (44 porcentaje), mientras que en 22 corazones (24,5 porcentaje) cursó alrededor de la cava. Se observó arteria en forma de ®S¼ en 14 casos (15,9 porcentaje del total de la muestra y 42,4 porcentaje de las originadas de la arteria circunfleja). La arteria del nodo atrioventricular se originó del segmento en ®U¼ invertida de la coronaria derecha, al nivel de la cruz cardiaca, en 81 corazones (92 porcentaje), y presentó un calibre proximal de 1,06 mm (más o menos 0,22). Con relación al calibre y al origen se evidencian hallazgos que coinciden con estudios previos. Se destaca la alta prevalencia de la arteria en forma de ®S¼ y de la trayectoria de la arteria sinoatrial alrededor de la vena cava superior.

The morphological expression of nodal arteries is important in the diagnosis and management of cardiac clinical events and surgical approaches. 88 nodal arteries of hearts obtained from autopsies were studied. Coronary arteries were injected with polyester resin pigmented with red. Morphological and morphometrical characteristics of nodal arteries were registered. The sinoatrial node artery had its origin in the right coronary artery in 52 cases (59,1 percentage), in the circumflex in 33 (37,35 percentage), and in both in 3 (3,4 percentage). Its proximal caliber was 1,31mm (more or less 0,3), corresponding to the arteries originated in the right coronary artery of 1,25 mm (more or less 0,3), while those that originated in the circumflex artery had a caliber of 1,42 mm (more or less 0,3), difference that was significant (p= 0,01). Its origin occurred more frequently in the anteriomedial third of both the right coronary artery and the circumflex artery (54,6 percentage and 61,2 percentage respectively). In its final segment, it crossed in most cases (44 percentage) in front of the cava vein, while in 22 hearts (24,5 percentage) went around the cava vein. In 14 cases the artery had an ®S¼ shape (15,9 percentage of the total sample and 42,4 percentage of those arising from the circumflex artery). The atrioventricular node artery was originated from the segment in inverted ®U¼ of the right coronary artery, at the level of the crux cardia in 81 hearts (92 percentage) and had a proximal caliber of 1,06 mm (more or less 022). In relation to the caliber and origin, the findings are consistent with previous studies. Prevalence of ®S¼ shape artery and trajectory of the sinoatrial artery around the superior cava vein are highlighted.

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