Background: Pregnancy may change maternal hemodynamic, which is considered a physiological mechanism for adaptation. Cardiac output tends to be influenced by reductions in vascular resistance and increases in uterine vasculature, as well as reduced autonomic tone combined with gestational physiological anaemia and increased blood volume due to increased plasma volume and hormonal mechanisms. In bitches, few studies have been conducted investigating the changes of the system and the clinical implications for the mother and foetuses due to poor cardiac adaptation during pregnancy.Materials, Methods & Results: Systolic blood pressure (SBP), electrocardiographic and Doppler echocardiographic measurements and serum sodium (Na), potassium (K), calcium (Ca) and phosphorus (P) levels were evaluated in six bitches of reproductive age. An evaluation was performed in oestrus (M0), followed by evaluations at 25 (M1), 45 (M2), and 60 days (M3) after the last natural or artificial insemination and 15 days after delivery (M4). For the statistical analysis, the means, medians and the standard deviation were calculated. The data were analysed using ANOVA and the Tukey test, with significance level of 5%. A descriptive analysis was performed for color Doppler in echocardiogram evaluation, cardiac axis and rhythm in electrocardiogram evaluation. In the electrolytic evaluation, significant differences were found only in the serum levels of Na, noticed as a reduction in M0-M1 and M3-M2 and an increase in M1-M2 and M3-M4. No significant differences were observed in the SBP, although there was a tendency to SBP reduction. ECG parameters were not significantly different, with no rhythm or conduction disturbances. There was not a significant difference in HR. Four animals (66.6%) had axis deviation to the right when comparing the oestrous phase with the final quarter of pregnancy. The echocardiographic parameters did not show significant changes.Discussion: The reduction observed in Na can occur by salt depletion, by dilutional or metabolic mechanisms. In contrast, the elevation in Na concentration could occur as a result of fluid and electrolyte retention by kidneys during gestation. The absence of electrocardiographic changes may be justified by the stability of mean serum potassium concentrations. An increase in HR five days before the expected calving time, demonstrating the maximum cardiac activity in this gestational phase, is related by other authors, therefore, in the present study, the absence of significant change in HR can be explained by the period in which the data collection was performed, 45 days of gestation, being therefore prior to the period of greatest HR. The cardiac axis deviation can be explained by the distension of the gravid uterus that cause compression of the adjacent organs, leading to diaphragmatic compression and consequent repositioning of the thoracic structures. A tendency to SBP reduction observed is directly influenced by peripheral vascular resistance and cardiac output that occur during pregnancy. Although the echocardiographic findings did not show changes, it is suggested that there are changes related to increased blood volume in pregnancy to provide an appropriate blood flow to the conceptus. It was concluded that pregnancy and the postpartum period in bitches did not cause changes in electrolytes levels, SBP values, echocardiographic and electrocardiographic parameters as compared to values obtained during oestrus.

RESUMO:A doença valvular crônica de mitral é a enfermidade cardíaca mais comumente relatada em cães de pequeno e médio porte, adultos ou idosos. A síncope cardíaca é uma manifestação comumente observada, causada por diversos mecanismos. Objetivou-se relatar um caso desta doença em uma cadela da raça Teckel, com 16 anos de idade, que apresentava episódios recorrentes de síncope. Os episódios estavam associados com bradicardia, palidez de mucosas e aumento da pressão intratorácica. Excluindo-se outras causas de síncope, foi realizado o diagnóstico presuntivo de síncope neurocardiogênica, sendo a primeira descrição na medicina veterinária. PALAVRAS-CHAVE: Cardiologia. Endocardiose. Reflexo de Bezold-Jarisch. Síncope vasovagal. NEUROCARDIOGENIC SYNCOPE IN A DOG WITH CHRONIC MITRAL VALVULAR DISEASE -CASE REPORTABSTRACT: Chronic mitral valvular disease is the most commonly acquired heart disease in middle-aged to elderly dogs in small to medium-size breeds. Cardiac syncope is a common manifestation observed in such disease, caused by several mechanisms. The purpose of this study is to report a case of several syncope episodes in a Teckel dog aged 16 years, presenting chronic mitral valvular disease. The episodes were associated with bradycardia, pale mucous membranes and increased intra-thoracic pressure. The presumptive diagnosis of neurocardiogenic syncope was reached by excluding other causes of syncope, which is the first description in veterinary medicine. KEYWORDS: Bezold-Jarisch reflex. Cardiology. Endocardiosis. Vasovagal syncope. SÍNCOPE NEUROCARDIOGÉNICO EN PERRO CON ENFERMEDAD VALVULAR MITRAL CRÓNICA -RELATO DE CASORESUMEN: La enfermedad valvular crónica de mitral es la enfermedad cardíaca más comúnmente reportada en perros de pequeño y mediano tamaño, adultos o ancianos. El síncope cardíaco es una manifestación comúnmente observada, causada por varios mecanismos. Esta investigación ha buscado relatar un caso de esta enfermedad en una perra de la raza Teckel, de 16 años de edad, que presentaba episodios recurrentes de síncope. Los episodios estaban asociados con bradicardia, palidez de mucosas y aumento de la presión intratorácica. Se ha excluido otras causas de síncope, se llevó a cabo el diagnóstico presuntivo de síncope neurocardiogénico, siendo la primera descripción en medicina veterinaria. PALABRAS CLAVE: Cardiología. Endocardiosis. Reflejo de Bezold-Jarisch. Síncope vasovagal. IntroduçãoA doença valvular crônica de mitral (DVCM) é a doença cardíaca adquirida mais comum em cães, que pode originar insuficiência cardíaca congestiva. É frequentemente reportada em cães adultos e idosos, de raças de pequeno e médio porte, sendo detectada em 30% dos cães com mais de 13 anos de idade (ABBOT, 2008). A síncope pode ser uma manifestação clínica de cães com esta doença. É definida como uma perda súbita e transitória da consciência, com iní-cio rápido e curta duração, ocorrendo recuperação espontâ-nea, rápida e completa (MOYA et al., 2009). Doenças cardíacas podem causar síncope por diminuição do débito cardíaco ...