Ultrasonographic assessment of maternal cardiac function and peripheral circulation during normal gestation in dogs

The aim of this study was to describe changes in cardiac morphology, systolic function and some peripheral hemodynamic parameters during normal pregnancy in dogs. Twenty healthy bitches, 10 pregnant (PG) and 10 non-pregnant controls (CG), were evaluated every 10 days using echocardiography from day 0 of the estrus cycle to parturition or to day 65 for the PG and CG groups, respectively. Systolic blood pressure (SBP) and uterine artery resistance index (RI) were also assessed. Throughout the study, the shortening fraction and cardiac output increased up to 30% vs. 5% (P<0.01) and 45% vs. 2% (P<0.01) in the PG and CG groups, respectively. In contrast, SBP and RI diminished up to 20% vs. 1% (P<0.01) and 29% vs. 0% (P<0.01) in the PG and CG groups, respectively. In conclusion, a decrease in afterload, an increase in cardiac output and cardiac hypertrophy appear to be the result of the hemodynamic modifications occurring during pregnancy in dogs.