Electrocardiographic markers of myocardial conduction and repolarization in Boxer dogs / Marcadores eletrocardiográficos de condução e repolarização miocárdica em cães da raça Boxer

ABSTRACT: Electrocardiographic markers have been used in people to classify arrhythmogenic risk. The aims of this study were to investigate electrocardiographic markers of conduction and repolarization in Boxers and non-Boxer dogs, and compare such findings between groups. Ten-lead standard electrocardiograms of Boxer dogs and non-Boxers recorded from 2015 to 2018 were retrospectively reviewed. Dogs >/ 4 years of age and weighing > 20kg were included. Animals with valvular insufficiencies, congenital cardiopathies, cardiac dilation, suspected systolic dysfunction, biphasic T-wave, bundle branch blocks, and those receiving antiarrhythmics were excluded. Electrocardiographic markers of conduction, QRS duration (QRSd) and dispersion (QRSD), and repolarization (corrected QT interval, Tpeak-Tend, JT and JTpeak), as well as derived indices, were measured. Two hundred dogs met the inclusion/exclusion requirements, including 97 Boxers (8.1±2.5 years old; 30±7kg) and 103 non-Boxer (8.8±2.5 years old, 30±8kg). QRSd and QRSD, and repolarization markers in lead II and left precordial lead V4 were considered similar between groups. Dispersion of late repolarization on lead rV2, Tpeak-Tend interval, was considered longer in Boxers (45±8ms vs 38±10ms, P=0.01). The Tpeak-Tend/JTpeak and the JTpeak/JT also differed between groups. Our results indicate that the dispersion of myocardial late repolarization in lead rV2 is slower in Boxers than other dog breeds.(AU)

Marcadores eletrocardiográficos têm sido estudados em seres humanos para estratificação do risco arritmogênico. Os objetivos deste estudo foram investigar os marcadores eletrocardiográficos de condução e repolarização miocárdica em Boxers e em cães de outras raças, e comparar tais resultados entre os grupos. Para tal, a eletrocardiografia convencional de 10 derivações registradas de 2015 a 2018 foram avaliadas de maneira retrospectiva. Cães com idade igual ou superior a 4 anos e pesando > 20kg foram incluídos. Animais com insuficiência valvar, cardiopatias congênitas, dilatação cardíaca, suspeita de disfunção sistólica, onda T bifásica, bloqueio(s) de ramo(s), ou aqueles que recebiam antiarrítmicos foram excluídos. Variáveis eletrocardiográficas de condução, como a duração e dispersão do complexo QRS (QRSd e QRSD, respectivamente), e repolarização (intervalo QT corrigido, Tpico-Tfinal, JT e JTpico), bem como índices derivados, foram mensurados. Duzentos cães que se adequaram aos critérios de inclusão/exclusão foram incluídos, 97 Boxers (8,1±2,5 anos; 30±7kg) e 103 não Boxers (8,8±2,5 anos; 30±8kg). O QRSd e o QRSD, e os marcadores de repolarização nas derivações II e V4 foram similares entre os grupos. O marcador de dispersão da repolarização tardia na derivação rV2, Tpico-Tfinal, foi considerado mais longo no Boxers (45±8ms vs 38±10ms, P=0.01). O Tpico-Tfinal/JTpico e o JTpico/JT também diferiram entre os grupos. Nossos resultados indicam que a dispersão da repolarização miocárdica tardia na derivação precordial direita, rV2, é mais lenta no Boxer do que nas outras raças.(AU)

Electrocardiographic markers of myocardial conduction and repolarization in Boxer dogs / Marcadores eletrocardiográficos de condução e repolarização miocárdica em cães da raça Boxer

Electrocardiographic markers have been used in people to classify arrhythmogenic risk. The aims of this study were to investigate electrocardiographic markers of conduction and repolarization in Boxers and non-Boxer dogs, and compare such findings between groups. Ten-lead standard electrocardiograms of Boxer dogs and non-Boxers recorded from 2015 to 2018 were retrospectively reviewed. Dogs >/ 4 years of age and weighing > 20kg were included. Animals with valvular insufficiencies, congenital cardiopathies, cardiac dilation, suspected systolic dysfunction, biphasic T-wave, bundle branch blocks, and those receiving antiarrhythmics were excluded. Electrocardiographic markers of conduction, QRS duration (QRSd) and dispersion (QRSD), and repolarization (corrected QT interval, Tpeak-Tend, JT and JTpeak), as well as derived indices, were measured. Two hundred dogs met the inclusion/exclusion requirements, including 97 Boxers (8.1±2.5 years old; 30±7kg) and 103 non-Boxer (8.8±2.5 years old, 30±8kg). QRSd and QRSD, and repolarization markers in lead II and left precordial lead V4 were considered similar between groups. Dispersion of late repolarization on lead rV2, Tpeak-Tend interval, was considered longer in Boxers (45±8ms vs 38±10ms, P=0.01). The Tpeak-Tend/JTpeak and the JTpeak/JT also differed between groups. Our results indicate that the dispersion of myocardial late repolarization in lead rV2 is slower in Boxers than other dog breeds.(AU)

Marcadores eletrocardiográficos têm sido estudados em seres humanos para estratificação do risco arritmogênico. Os objetivos deste estudo foram investigar os marcadores eletrocardiográficos de condução e repolarização miocárdica em Boxers e em cães de outras raças, e comparar tais resultados entre os grupos. Para tal, a eletrocardiografia convencional de 10 derivações registradas de 2015 a 2018 foram avaliadas de maneira retrospectiva. Cães com idade igual ou superior a 4 anos e pesando > 20kg foram incluídos. Animais com insuficiência valvar, cardiopatias congênitas, dilatação cardíaca, suspeita de disfunção sistólica, onda T bifásica, bloqueio(s) de ramo(s), ou aqueles que recebiam antiarrítmicos foram excluídos. Variáveis eletrocardiográficas de condução, como a duração e dispersão do complexo QRS (QRSd e QRSD, respectivamente), e repolarização (intervalo QT corrigido, Tpico-Tfinal, JT e JTpico), bem como índices derivados, foram mensurados. Duzentos cães que se adequaram aos critérios de inclusão/exclusão foram incluídos, 97 Boxers (8,1±2,5 anos; 30±7kg) e 103 não Boxers (8,8±2,5 anos; 30±8kg). O QRSd e o QRSD, e os marcadores de repolarização nas derivações II e V4 foram similares entre os grupos. O marcador de dispersão da repolarização tardia na derivação rV2, Tpico-Tfinal, foi considerado mais longo no Boxers (45±8ms vs 38±10ms, P=0.01). O Tpico-Tfinal/JTpico e o JTpico/JT também diferiram entre os grupos. Nossos resultados indicam que a dispersão da repolarização miocárdica tardia na derivação precordial direita, rV2, é mais lenta no Boxer do que nas outras raças.(AU)

Conduction system in the swine heart: essential landmarks for gross dissection

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)

Conduction system in the swine heart: essential landmarks for gross dissection

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...