Electrocardiographic Changes in Normal and Abnormal Canine Pregnancy

Abstract

The aim of this study was to describe the canine electrocardiographic changes in the course of normal and abnormal pregnancy. Twenty-three Brucellosis-negative pregnant bitches were retrospectively classified as normal (n = 12) or abnormal (n = 11). A control group of non-pregnant dioestrous bitches (n = 10) was also included. Normal pregnant females delivered healthy puppies at term while abnormal animals interrupted their pregnancy between days 52-60 (from estimated luteinizing hormone peak) or presented perinatal litter death higher than 60%. All the bitches were electrocardiographically evaluated every 10 days from day 0 to day 65 of the oestrous cycle, to parturition or abortion. Percentage heart rate change increased 31.3% from day 40 to 60 in normal gestation while it decreased -1.8% in dioestrous bitches, although it did not change in the abnormal group (p < 0.01). In the abnormal pregnant group but not in the others, percentage QRSa change fell to -34% on day 60 (p < 0.01). At the same time point, percentage QRSd change was 6.2% vs -4.9% in normal gestations and dioestrous animals, respectively (p < 0.05). Corrected QT interval augmented from day 40 onwards up to 9.9% and 4.3% in the normal pregnant and dioestrous groups, respectively, while it remained unchanged in abnormal gestations (p < 0.05). It is concluded that during normal canine pregnancy, some electrocardiographic parameters begin changing from day 40 onwards, and that pathological gestations differ from normality from day 30. The use of electrocardiography in canine obstetrics might contribute to identify abnormal outcomes before they become clinically evident.

Effect of pregnancy and correlation of weight and heart rate with electrocardiographic parameters in the American Miniature Horse

“…With increased blood volume, the atrium is also dilated in a compensatory manner, thereby elevating the amplitude of the P wave. These anatomical and functional adaptations also affect the cardiac conduction system, resulting, in some cases, in an increase in the QT interval during pregnancy (Blanco et al, 2012). However, this effect was not observed in the horse breed examined in this study.…”

“…These changes include an increase in total blood volume and cardiac output associated with myocardial hypertrophy. Furthermore, during pregnancy, peripheral vascular resistance decreases, and uterine blood flow increases, which also affect the cardiac conduction system (Lamb et al, 2010;Blanco et al, 2012). These changes are observable by ECG, and some published studies have described the effects of reproductive status on ECG parameters in several breeds of horses, including Thoroughbred (Fernandes et al, 2004), Mangalarga (Vicenzi et al, 2000) and ponies (Rezakhani et al, 2010).…”

Hormonal, Electrolytic, and Electrocardiographic Evaluations in Bitches With Eutocia and Dystocia

“…6,7 In the fetus, thyroid hormones are important for development of the neural and skeletal systems. 8,9 Cardiac arrhythmia is the main cardiovascular change observed during the last 40 days of gestation and in normal parturition, which shows the importance of understanding physiological events in bitches to identify cardiac abnormalities, 10 especially during dystocia, which requires anesthesia and surgery.…”

Cardiovascular Evaluation in Bitches in Oestrus, Pregnancy and Puerperium

“…In the present study, the absence of electrocardiographic changes may be justified by the stability of mean serum potassium concentrations. The literature suggests that the electrocardiographic changes found during gestation in bitches may be associated with electrolyte abnormalities, especially serum K [4,9].…”

“…Most reports of cardiac abnormalities are on women and rats and are considered to be physiological mechanisms for adaptation of the cardiovascular system to volume overload caused by pregnancy. In bitches, few studies have been conducted investigating the changes suffered by the system and the clinical implications for pregnant animals and foetuses due to poor cardiac adaptation during pregnancy [4,5]. Therefore, the aim of this study was to investigate cardiovascular and electrolyte changes in bitches during oestrus and pregnancy stages, and the early postpartum period.…”