The effect of pregnancy on echocardiographic variables in healthy bitches

Little is known of the effect of pregnancy on canine cardiovascular function. This study was undertaken to evaluate the effect of pregnancy on canine echocardiographic variables. Serial echocardiographic examinations of 7 healthy, sexually intact female canine mongrels dogs that weighed between 9.7 and 13.4 kg were performed. The subjects were examined prior to ovulation, during early pregnancy, during late pregnancy within 6 days of parturition and again, after puppies were weaned. Repeated measures ANOVA disclosed a statistically significant effect of time on end-systolic left ventricular dimension (LVIDs, p = 0.005), left ventricular fractional shortening (%FS, p = 0.001), Doppler-derived inflow and ejection velocities (all p < 0.05), as well as on heart rate (HR, p = 0.03). %FS, HR, aortic ejection velocity, pulmonic ejection velocity and early diastolic mitral inflow velocity were maximal during late pregnancy. The increase in %FS resulted from a decrease in LVIDs. For Doppler-derived flow velocities, the range of differences of least square means (m/s) between early and late pregnancy was 0.21–0.32. While the magnitude of effect generally was small, this study provides evidence that pregnancy in healthy bitches is associated with changes in echocardiographic variables.