Elsevier

Theriogenology

Volume 78, Issue 6, 1 October 2012, Pages 1235-1242
Theriogenology

Research article
Echocardiographic and Doppler assessment of maternal cardiovascular function in normal and abnormal canine pregnancies

https://doi.org/10.1016/j.theriogenology.2012.05.019Get rights and content

Abstract

The objective was to verify maternal hemodynamic differences between normal and abnormal pregnancies in dogs. Brucella-negative pregnant bitches (n = 31) were retrospectively classified into abnormal (which had either their pregnancy interrupted between Days 52 and 60 or perinatal death of more than 50% of the litter; n = 14) and normal (which had delivered healthy puppies at term; n = 17). These dogs were evaluated with echocardiography every 10 days from Days 0 to 60 of gestation (Day 0 = estimated day of LH peak). Systolic blood pressure was also assessed. At Day 50 of gestation, left ventricular free wall in systole increased in the normal but not in the abnormal group (P < 0.01). In contrast, end systolic stress (P < 0.01) and systolic blood pressure (P < 0.01) diminished only in normal animals. We concluded that signs of altered maternal cardiovascular adaptation to pregnancy may be predictors of obstetrical complications in dogs.

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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