Eletrocardiografia computadorizada em cadelas com tumores mamários / Electrocardiography in bitches with mammary tumors

The incidence of cancer has increased due to greater longevity of the animals as a consequence of better control of other diseases, improvement of nutrition and good practices in preventive medicine. Malignant tumors can cause paraneoplastic syndrome such as hypercalcemia, anemia, cachexia, among others and consequent cardiovascular disorders. The electrocardiography (ECG) is a complementary exam that can reveal with its traces these rhythmic disorders. Based on that, the objective of this study was to evaluate the ECG in bitches with mammary tumors in order to detect in which type of tumor would be found significant changes as in cardiac rhythm, ECG waves, segments or cardiac axis. Twenty-nine female dogs were used in this study, being 19 bitches with mammary tumor, and they were allocated in three groups: G1: control group (n = 10), G2: benign neoplasia group (n = 6) and G3: malignant neoplasia group (n = 13). The most prevalent type of neoplasia in G2 was the benign mixed tumor (83%), followed by adenoma (17%) whereas in G3: carcinoma in mixed tumor (61%); papillary carcinoma (23%). Regarding cardiac rhythm, it was found sinus arrhythmia (SA) and normal sinus rhythm (NS): G1: 50% SA and 50% NS; G2: 67% SA and 33% NS; G3: 54% SA and 46% NS. No ventricular or atrial arrhythmias were detected. For other parameters in G1, G2 and G3, respectively (mean ± Std error): FC (bpm): 110±9.2, 120 ± 8.5, 124±7,5; P (ms): 48 ± 1.6, 51 ± 1.8, 50 ± 1.2; P (mV) 0.19 ± 0.02, 0.2 ± 0.02, 0.19 ± 0.02; PR (ms): 94 ± 4.3, 93 ± 5.5, 89 ± 3.9; QRS (ms): 56 ± 1.54, 60 ± 4, 62 ± 1.2; R (mV): 1.1 ± 0.06, 1.2 ± 0.24, 0.9 ± 0.13; QT (ms): 203 ± 9.4; 204 ± 7.9; 182 ± 15.6; and cardiac axis (°): 66 ± 6.2, 61 ± 7.9, 70 ± 7.5. There were no significant differences for all cardiac parameters and also for ST interval and T wave morphology. All electrocardiographic parameters found are in accordance with other studies carried out in the canine species. The results regarding tumor types differ from what was found in another study, in which in 18 bitches with mammary tumors, 55% were benign, with prevalence of adenomas (38%) followed by benign mixed tumors, and 45% malignant, with adenocarcinoma prevailing (22%). In another study, it was verified in 63 bitches the predominance of tubular carcinoma (26.56%) and carcinoma in mixed tumors (23.44%). Diverging from the electrocardiographic parameters of this study, a significant difference was found in the R wave amplitude value in the research by Barros et al., (2015) who performed computerized electrocardiography in 50 dogs, not only with mammary neoplasms (55% mammary carcinomas), but also in mastocytomas, lymphomas, benign tumors and other sarcomas. This author found out that the R wave amplitude values of the neoplasia group were lower when compared to the control group. In addition, we suspect that other types of tumors could result in more paraneoplastic syndrome than the mammary neoplasms found in this research. Neoplasms as lymphomas (T cells), apocrine gland anal sac adenocarcinomas, multiple myelomas and thymomas are known as a cause of hypercalcemia of malignancy and histiocytic sarcomas, myelomas, leukemia and lymphomas causing anemia. In conclusion, ECG has no changes in benign or malignant mammary tumors in dogs. However, this fact does not exclude the importance of its performance in pre-anesthetic evaluations. Further studies with a larger sample including the clinical staging of these bitches with a balanced number of animals with low and high staging are suggested.(AU)

Correlation between systolic function and presence of myofibroblasts in doxorubicin-induced cardiomyopathy / Correlação entre função sistólica e presença de miofibroblastos na cardiomiopatia induzida pela doxorrubicina

ABSTRACT: Cardiotoxicity induced by doroxubicin generates systolic disfunction and myocardial remodeling with presence of myofibroblasts. These cells are thought to be attracted to the injured heart to avoid the development of congestive heart failure. The objective of this study was to evaluate the systolic dysfunction generated by doxorubicin through Doppler echocardiography, and its correlation with the presence of myofibroblasts in the myocardium. Twenty-five New Zealand White rabbits were divided into two groups (control, and treated with doxorubicin). The drug was administered for six weeks; Doppler echocardiography was performed before the first, and after the last administration of doxorubicin. Immuno detection of myofibroblasts was performed by immunohistochemistry. The treated group exhibited significant reduction in systolic function as assessed by Doppler echocardiography, and increased frequency of myofibroblasts, which were present in similar amounts in the left ventricle, interventricular septum, and right ventricle. There was a significant negative correlation between number of myofibroblasts in the interventricular septum and in the left ventricle with systolic function indices, which reveals that the higher the number of fibroblasts, the worst systolic function is in rabbits treated with doxorubicin. Increase in myofibroblast numbers was not sufficient to preserve systolic function.

RESUMO: A cardiotoxicidade induzida pela doxorrubicina gera disfunção sistólica e remodelamento miocárdico, com presença de miofibroblastos. Acredita-se que essas células sejam atraídas para a não evolução do quadro de insuficiência cardíaca congestiva. O objetivo do presente trabalho foi avaliar a função sistólica gerada pela doxorrubicina por meio da ecodopplercadiografia e correlacioná-la com a presença de miofibroblastos no miocárdio. Foram utilizados 25 coelhos da raça Nova Zelândia, alocados em dois grupos (controle e tratados com doxorrubicina). O fármaco foi administrado por seis semanas e a ecodopplercardiografia foi realizada no momento zero e após a última administração da doxorrubicina. A imunodetecção dos miofibroblastos foi realizada por imuno-histoquímica. Houve redução significativa na função sistólica, observada na ecodopplercardiografia e aumento na imundetecção dos miofibroblastos nos animais tratados, na mesma intensidade no ventrículo esquerdo, septo interventricular e ventrículo direito. Houve correlação negativa significativa entre o número de miofibroblastos no septo interventricular e no ventrículo esquerdo com os índices de função sistólica, revelando que quanto mais miofibroblastos presentes, pior é a função sistólica de coelhos tratados com doxorrubicina. O aumento do número de miofibroblastos não foi suficiente para manutenção da função sistólica.

High-resolution electrocardiography in the diagnosis of arrhythmogenic right ventricular cardiomyopathy in Boxer dogs / Eletrocardiografia de alta resolução no diagnóstico da cardiomiopatia arritmogênica do ventrículo direito em cães da raça Boxer

To evaluate the reliability of high-resolution electrocardiography in the diagnosis of arrhythmogenic right ventricular cardiomyopathy in Boxers, 20 dogs with no structural cardiac alterations at echocardiographic examination were grouped on the basis of frequency of ventricular arrhythmias, evaluated by 24-hour ambulatory ECG, and undergoing a high-resolution electrocardiography. High frequency QRS duration, duration of terminal QRS complex less than 40µV (LAS40) and root mean square voltage of the terminal 40 milliseconds of the QRS complex (RMS40) were measured. Differences in high-resolution ECG variables were not observed between groups. Therefore, the results of this investigation suggest that high-resolution electrocardiography is not a useful method for the diagnosis of arrhythmogenic right ventricular cardiomyopathy in Boxers without detectable myocardial alterations or systolic dysfunction.

Com o objetivo de avaliar a importância da eletrocardiografia de alta resolução no diagnóstico da cardiomiopatia arritmogênica do ventrículo direito do Boxer, 20 cães sem evidências de doença cardíaca estrutural à avaliação ecodopplercardiográfica foram agrupados de acordo com a frequência de arritmias ventriculares, avaliadas pela eletrocardiografia ambulatorial de 24 horas, e submetidos ao exame eletrocardiográfico de alta resolução. Duração do complexo QRS filtrado, duração dos sinais de baixa amplitude (menor que 40µV) dos últimos 40 milissegundos do complexo QRS e raiz quadrada média da voltagem ao quadrado dos últimos 40 milissegundos do complexo QRS (RMS40) foram as variáveis avaliadas. Não foram observadas diferenças significativas entre os grupos em relação às variáveis estudadas. Sendo assim, os resultados do presente estudo sugerem que a eletrocardiografia de alta resolução não é uma ferramenta útil no auxílio diagnóstico da cardiomiopatia arritmogênica do ventrículo direito dos cães da raça Boxer que não apresentam alterações miocárdicas evidentes ou disfunção sistólica.

Diferentes frações inspiradas de oxigênio em coelhos hipovolêmicos anestesiados com propofol e submetidos à ventilação mecânica / Different fractions of inspired oxygen in hypovolemic rabbits anesthetized with propofol and maintained in mechanic ventilation

Avaliaram-se os efeitos do fornecimento de diferentes frações inspiradas de oxigênio (FiO²) em coelhos hipovolêmicos, anestesiados com infusão contínua de propofol e mantidos em ventilação controlada sobre os parâmetros respiratórios, hemogasométricos e hemodinâmicos. Foram utilizados 50 coelhos (Nova Zelândia), pesando 3,5±0,3kg, distribuídos em 5 grupos: G100 (FiO²=1), G80 (FiO²=0,8), G60 (FiO²=0,6), G40 (FiO²=0,4) e G21 (FiO²=0,21), os quais receberam xilazina (1mg kg-1) e cetamina (15mg kg-1) pela via intramuscular. Transcorridos 20 minutos, foi administrado propofol (8mg kg-1 bolus e 0,5mg kg-1 min-1) e rocurônio (0,6mg kg-1 bolus e 0,6mg kg-1 h-1). Iniciou-se então, a ventilação mecânica no modo pressão controlada. Após 30 minutos, os animais foram submetidos à hipovolemia aguda, retirando-se sangue arterial (12mL kg-1). Os parâmetros foram mensurados 30 minutos após a indução anestésica (M0) e a cada dez minutos depois da exsanguinação (M1- M7). As variáveis foram submetidas à análise de variância seguida pelo teste de Tukey (P<0,05). Os valores de PaO², SaO², P A O², AaDO² diminuíram quanto mais baixas foram as FiO². Após a indução da hipovolemia, as variáveis DC, PAM, PaO², SaO², Vt, AaDO² diminuíram significativamente. Nenhuma alteração foi notada nos parâmetros FC e PaCO². As FiO² de 0,8 e 1,0 mostraram-se as mais indicadas por manter melhor estabilidade ventilatória e adequada troca gasosa.

The effects of several inspired oxygen fractions (FiO²) on the blood gases, respiratory and hemodynamic parameters in mechanical ventilation hypovolemic rabbits anesthetized with continuous infusion of propofol were evaluated. A total of 50 rabbits (New Zealand), weighing 3.5±0.3kg, were divided into five groups: G100 (FiO²=1), G80 (FiO²=0.8), G60 (FiO²=0.6), G40 (FiO²=0.4) and G21 (FiO²=0.21), which received xylazine (1mg kg-1) and ketamine (15mg kg-1) intramuscularly. Exactly after 20 minutes, it was administered propofol (8mg kg-1 bolus and 0.5mg kg-1 min-1) and rocuronium (0.6mg kg-1 bolus and 0.6mg kg-1 h-1. Then, the mechanical ventilation by controlled pressure mode began. After 30 minutes, the animals underwent acute hypovolemia, withdrawing arterial blood (12mL kg-1). The parameters were measured 30 minutes after anesthetic induction (M0) and every ten minutes after exsanguination (M1-M7). The variables were subjected to analysis of variance followed by Tukey test (P<0.05). The values of PaO², SaO², PAO², AaDO² decreased as lower were the FiO². After the induction of hypovolemia, the variables CO, MAP, PaO², SaO², Vt, AaDO² decreased significantly. No change was noted in the parameters HR and PaCO². The FiO² of 0.8 and 1.0 proved to be the most suitable for maintaining stability, better ventilation and adequate gas exchange.