Research articleEchocardiographic and Doppler assessment of maternal cardiovascular function in normal and abnormal canine pregnancies
Introduction
Maternal cardiac adaptation during gestation plays a major role in uterine perfusion to support fetal development [1], [2], [3]. A diminution in afterload, an increment in systolic function and cardiac hypertrophy appeared to result from hemodynamic modifications occurring during normal canine pregnancy [4], [5]. In this species, cardiac morphology was characterized by an increment in left ventricular end diastolic diameter (LVDd), left ventricular wall thickening and a diminution in left ventricular end systolic diameter (LVDs) during the second half of gestation [4], [5]. Furthermore, the shortening fraction (SF) and velocity of circumferential fiber shortening (Vcf) increased from Day 30 of gestation onwards, whereas end systolic stress (ESS) diminished during the same period [4]. These functional changes could be related to the improvement in systolic function, an increase in blood volume, and a decrease in systemic blood pressure that occur during pregnancy.
The reduction in uterine artery resistance index (RI) that occurs during gestation represents a contribution of 20 to 26% to the diminution of total vascular resistance [2], [5]. In addition, diminution of the peripheral resistance is a major determinant of the augmentation of stroke volume (SV) and cardiac output (CO) that characterize pregnancy [4], [6].
In women, maternal cardiovascular maladaptation is highly correlated with adverse pregnancy outcomes, including pre-eclampsia, intrauterine growth restriction, placental abruption, or stillbirth [7], [8], [9]. There is evidence that intrauterine growth restriction is associated with impaired expansion of the maternal intravascular space and a lack of CO increase [10]. In addition, poor uterine perfusion is associated with gestational hypertension [11].
In dogs, peripheral circulation has been described through uterine blood flow in an experimental model of abnormal gestation [12] and also in spontaneous cases [13]. However, there are apparently no reports regarding cardiac structure and function during spontaneous abnormal pregnancy. Cardiac function and morphology of pregnant bitches destined to have complications may differ from those with a normal outcome. Thus, assessment of maternal left ventricular structure with the evidence of an altered geometry may provide important prognostic information. Therefore, the aim of this study was to describe changes in cardiac morphology, systolic and diastolic function, and systolic blood pressure, during late abnormal pregnancy in dogs.
Section snippets
Animals and follow up
Thirty-one purebred (various breeds) pregnant bitches, 1 to 8 yrs (3.4 ± 1.9), weighing 3 to 50 kg (20.3 ± 16.7) were recruited into this study. At the beginning of the study, all bitches were clinically healthy and cardiac examinations did not reveal any abnormality. All bitches were Brucellosis-negative and retrospectively classified as normal and abnormal pregnancy. The abnormal group (n = 14) included those in which pregnancy spontaneous interruption occurred between Days 52 and 60 (Day 0 was
Results
Both groups of patients were similar, on the basis of BW, age, litter size, and parity. At the beginning of the study, cardiovascular parameters did not differ between groups and all dogs had values within the normal range for their BW [20], [30], [31]; Table 1]. There were interactions between time and group for percentage LVDs (P < 0.05), LVFWs (P < 0.01), ESS (P < 0.01) and SBP (P < 0.01) changes throughout the study (Table 2). Percentage LVDs change decreased in the normal group, but not in
Discussion
In this study, normal pregnant bitches were characterized by cardiac hypertrophy and increasing inotropy. These findings were consistent with previous reports during physiological canine gestation where left ventricular wall thickness augmented, whereas LVDd increased and LVDs decreased [4], [5]. The present normal animals developed increasing LVFWs, whereas this parameter remained constant in pathologic cases. These results were also consistent with those of Novelli, et al. (2003) [9], who
Acknowledgments
This study was partially funded by the University Incentive Program of Teaching and Research 11/V164. PGB and CG are Research Fellow and Career Scientist, respectively of the National Research Council (CONICET) of Argentina.
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2018, Research in Veterinary ScienceCitation Excerpt :The same pattern has been observed in guinea pigs (Hart et al., 1985). On the other hand, studies carried out on dogs (Abbott, 2010; Blanco et al., 2012; Blanco et al., 2011; Williams et al., 2007) have shown significant increase of CO only in the second half of pregnancy. Our results may show species-specific characteristics since in rats in which also both SV and HR increase contributes to CO rise, the pattern opposite to ours has been observed – sole SV increase in the first half of pregnancy and concomitant increase of SV and HR in the second one (Slangen et al., 1996).
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2018, Animal Reproduction ScienceCitation Excerpt :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). Same results were related in previous studies in bitches (Abbott, 2010; Blanco et al., 2012) but without an significant increase in the thickness of the myocardial wall or karyometry analysis which allows them to reach this conclusion (Liberatori Filho et al., 1998). It is therefore inferred that, the absence of myocardial remodeling evidence in bitches is probably due to the shorter gestation length, in which structural changes of the myocardium do not reach the magnitude of those for humans.