Cardiac parameters during the estrous cycle of canine bitches

Abstract

The cardiovascular parameters of canine bitches were assessed during the estrous cycle. A total of eleven mongrel female dogs were enrolled in a longitudinal prospective investigation. Six animals were bred during the study and were assigned into group I, in which evaluations were performed during proestrus, estrus, gestational diestrus and anestrus. The five remaining bitches were not bred and underwent evaluations during proestrus, estrus, nongestational diestrus and anestrus. The holter data showed a gradual increase in the minimum and mean heart rate along pregnancy, as well as a reduction during anestrus, which differed significantly among the distinct periods. The values for maximal heart rate documented during pregnancy were significantly lower than those recorded during anestrus, and a variation in the heart rate circadian rhythm was also found, as demonstrated by decreases at night and rises during the day. Cardiac rhythm had a similar performance in both pregnancy and anestrus. Likewise, the blood pressure, electrocardiography, and echocardiography data did not vary during the estrous cycle. The results support the role played by the autonomic nervous system during these two distinct periods in order to attain a heart rate that provides the blood needed by the female’s body during the various stages of the reproductive cycle. Further studies are needed to better clarify the cardiovascular compensatory neuroendocrine events that accompany gestation in this species.

Influence of estrous cycle and gestation on cardiovascular system of bitches

“…These changes probably occurred due to a more effective systolic performance and to an increase in ventricular compliance. These results are consistent with findings in previous studies (Abbott, 2010;Blanco et al, 2011;Blanco et al, 2012;Souza et al, 2017).…”

“…This response occurs so the heart rate does not increase to harmful rates during gestation and cause damage to the cardiovascular system. Variables relating to the thickness and diameter of the cardiac chambers were not different when compared among the reproductive stages evaluated in the present study, these findings are consistent with the results of Souza et al (2017). In contrast in women was reported an physiological hypertrophy of the eccentric type as consequence of hemodynamic overload, when the myocardium adapts by Frank-Starling mechanism (Eghbali et al, 2005;Fok et al, 2006;Patey et al, 2017).…”

“…Heart Rate did not vary and these findings are consistent with those of Souza et al (2017), where vagal tone was found to downregulate the heart rate in response to an increase in the hemodynamic demand. This response occurs so the heart rate does not increase to harmful rates during gestation and cause damage to the cardiovascular system.…”

“…Characterization of the cardiovascular system adaptations in pregnant bitches has been an object of studies in veterinary medicine, revealing the importance of these variables to myocardial contractility (systolic function) and cardiac output (Blanco et al, 2012;Souza et al, 2017). The paucity of information in this species provides opportunities for more detailed evaluation of the echocardiographic variables such as relaxation capacity and compliance of this organ (diastolic function) during the gestation of healthy bitches.…”

Effects of the estrous cycle and pregnancy status on cardiovascular variables in healthy bitches

“…Previous investigations have variably documented increases in LV size and wall thickness [17,18], LV systolic function [17,19,20], transvalvular blood flow velocities [19], and echocardiographic estimates of SV and CO [17,18] during late pregnancy in healthy bitches, but this suite of findings is not reproduced in all studies [21]. These studies have also variably reported decreases in LA size [19], systolic myocardial wall stress [17], and systolic BP [17,22] during the course of pregnancy.…”