Physical Activity and Diabetes Laboratory, Faculty of Kinesiology, Sport and Recreation, Women and Children's Health Research Institute, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.
Departments of Medicine and Obstetrics and Gynecology, Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.
J Appl Physiol (1985). 2021 Apr 1;130(4):923-932. doi: 10.1152/japplphysiol.00707.2020. Epub 2020 Dec 24.
In conjunction with significant cardiovascular adaptation, changes in cardioautonomic balance, specifically greater sympathetic activation and vagal withdrawal, are considered normal adaptations to healthy singleton pregnancy. Cardiovascular adaptation to twin pregnancy is more profound than that of singleton pregnancies; however, the changes in cardioautonomic control during multifetal gestation are unknown. To address this gap, beat-by-beat blood pressure (photoplethysmography) and heart rate (lead II electrocardiogram) were measured continuously in 25 twin pregnancies and 25 singleton pregnancies (matched for age, prepregnancy body mass index, and gestational age) during 10 min of rest. Data extracted from a 3- to 5-min period were used to analyze heart rate variability (HRV), blood pressure variability (BPV), cardiovagal baroreflex gain, and cardiac intervals as indicators of cardioautonomic control. Independent tests were used to determine statistical differences between groups (α = 0.05), and the false rate discovery was determined to adjust for multiple comparisons. Resting heart rate was greater in twin compared with singleton pregnancies (91 ± 10 vs. 81 ± 10 beats/min; = 0.001), but blood pressure was not different. Individuals with twin pregnancies had lower HRV, evidenced by lower standard deviation of R-R intervals (32 ± 11 vs. 47 ± 18 ms; = 0.001), total power (1,035 ± 810 vs. 1,945 ± 1,570 ms; = 0.004), and high frequency power (224 ± 262 vs. 810 ± 806 ms; < 0.001) compared with singleton pregnancies. There were no differences in cardiac intervals, BPV, and cardiovagal baroreflex gain between groups. Our findings suggest that individuals with twin pregnancies have greater sympathetic and lower parasympathetic contributions to heart rate and that cardiac, but not vascular, autonomic control is impacted during twin compared with singleton pregnancy. Individuals with healthy twin pregnancies had lower overall heart rate variability compared with those with singleton pregnancies at similar gestational ages. These results suggest a greater sympathetic and reduced parasympathetic contribution to cardiac control in twin pregnancies. Baseline heart rate was elevated, while arterial pressure and spontaneous cardiovagal baroreflex gain were not different between groups. This was result of the upward resetting of the cardiovagal baroreflex during healthy twin pregnancy, thus maintaining arterial pressure.
在伴随显著心血管适应的同时，心脏自主平衡的改变，特别是交感神经激活和迷走神经抑制的增加，被认为是健康单胎妊娠的正常适应。与单胎妊娠相比，双胎妊娠的心血管适应更为显著；然而，多胎妊娠期间心脏自主控制的变化尚不清楚。为了解决这一差距，我们连续测量了 25 例双胎妊娠和 25 例单胎妊娠（年龄、孕前体重指数和孕龄匹配）在 10 分钟休息期间的每搏血压（光体积描记法）和心率（导联 II 心电图）。从 3-5 分钟的时间段中提取的数据用于分析心率变异性（HRV）、血压变异性（BPV）、心脏迷走反射增益和心脏间期，作为心脏自主控制的指标。独立检验用于确定组间的统计学差异（α=0.05），并确定虚假发现率以调整多重比较。与单胎妊娠相比，双胎妊娠的静息心率更高（91±10 次/分 vs. 81±10 次/分； = 0.001），但血压无差异。双胎妊娠个体的 HRV 较低，表现为 R-R 间期标准差较低（32±11 毫秒 vs. 47±18 毫秒； = 0.001），总功率较低（1035±810 毫秒 vs. 1945±1570 毫秒； = 0.004），高频功率较低（224±262 毫秒 vs. 810±806 毫秒； < 0.001）。与单胎妊娠相比，两组之间的心脏间期、BPV 和心脏迷走反射增益无差异。我们的研究结果表明，双胎妊娠个体的心率受到更大的交感神经和较低的副交感神经贡献，而心脏自主神经控制而不是血管自主神经控制在双胎妊娠中受到影响。与单胎妊娠相比，具有健康双胎妊娠的个体在相似的孕龄时，整体心率变异性较低。这些结果表明，双胎妊娠中存在更大的交感神经和减少的副交感神经对心脏控制的贡献。基础心率升高，而两组之间的动脉压和自发心脏迷走神经压力反射增益没有差异。这是由于健康双胎妊娠期间心脏迷走神经压力反射的向上重置，从而维持了动脉压。
