Uterine haemodynamics in young and aged pregnant mares measured using Doppler ultrasonography

Abstract

SummaryReason for performing study: Aged mares with endometrosis suffer higher rates of pregnancy loss than young mares, due to poor placental development. Reduced uterine blood supply may be one contributory factor. Objectives: To measure uterine artery (UA) blood flow and other Doppler indices throughout pregnancy and compare placental and foal development in young mares and aged mares. Methods: Thoroughbred mares were grouped according to age and endometrial biopsy score: 1) 6 young mares (mean age 7.3 years, Category I); 2) 6 aged mares (mean age 18.3 years, Category II). Vascular pathology was nil or mild except in one aged mare with moderate perivasculitis. Both UA were scanned fortnightly throughout pregnancy. Total blood flow volume (BFV, ml/min/kg bwt), peak systolic velocity (PSV, cm/s) and resistance index (RI) were determined by pulsed wave, Doppler ultrasound and UA diameter using B-mode. Mixed-effects regression analyses were used to relate vascular parameters with different predictive variables, whilst accounting for the multiple repeated measurements taken from individual horses through the duration of their pregnancies. Results: PSV, RI and total BFV were best predicted by stage of pregnancy (P<0.001; r 2 >78%). The UA diameter was also associated with stage of pregnancy (P<0.001; r 2 = 87%) and was significantly greater in the gravid horn (P<0.001). There was a tendency for lower total BFV in older mares (P<0.05) and they delivered lighter foals than young mares (P<0.05). Gross placental morphometry was similar, but microscopic surface density of the microvilli was lower (P<0.02), in aged than young mares. Conclusions and potential relevance: Increased uterine blood flow and decreased vascular resistance reflect fetal growth and development of the placental microcirculation. Older mares have poorer placental microvillus development and lighter foals with reduced UA blood flow. Poor uterine blood flow may be an important contributory factor for pregnancy loss in aged mares.

Doppler Ultrasonographic Estimation of Renal Resistive Index in Horse: Comparison Between Left and Right Kidneys

“…Doppler ultrasonography in the equine medicine has been widely applied in echocardiography [28][29][30] and to assess blood flow in digital, uterine, and renal arteries [3][4][5]7,8,31]. Resistive index is an indicator of vascular resistance.…”

“…Cipone et al [6] showed the features of the equine common carotid artery obtained with the pulsed-wave Doppler. Few studies reported the use of Doppler ultrasonography to evaluate the equine reproductive apparatus [7,8].…”

Principais Aplicações Da Ultrassonografia Modo Doppler Na Reprodução Em Éguas

“…Esta modalidade pode ser utilizada para avaliar a hemodinâmica diretamente do tecido alvo, como endométrio, parede folicular e corpo lúteo (CL) (OUSEY et al, 2012;LEMES et al, 2015;ABDELNABY et al, 2016). O modo color Doppler é subdividido em dois modos distintos: Color-flow e Power-flow.…”

“…A pobre vascularização do sistema reprodutivo tem sido associada à subfertilidade ou infertilidade em éguas, podendo causar deficiências em sinalização hormonal, contratilidade uterina, placentação e interação materno-fetal (LEBLANC, 2010;OUSEY et al, 2012). Em mulheres, demonstrou-se que o baixo fluxo de sangue nas artérias uterina e ovariana no período luteal está associado à infertilidade (RAZIK et al, 2015).…”

“…Entretanto, a capacidade como ferramenta diagnóstica da Ultrassonografia modo color Doppler ainda não está completamente elucidada, o que requer estudos detalhados para que possa ser considerada como tal. Dessa forma, estudos envolvendo sua aplicação estão sendo realizados visando ampliar o conhecimento fisiológico e em enfermidades do sistema reprodutor equino (SILVA et al, 2005;OUSEY et al, 2012;ALONSO et al, 2014).…”