Description
Women who have had preeclamptic pregnancies are at risk for life-long cardiovascular disease. However, the factors contributing to this risk have yet to be established. Sympathetic nervous system dysregulation has been proposed to contribute to cardiovascular dysfunction during preeclamptic pregnancies. Therefore, we examined muscle sympathetic nerve activity (MSNA) at baseline and during a chemoreflex stimulus in women 6-24 months postpartum following a preeclamptic pregnancy (PE; n=6, age 28±2 y, BMI 27±3 kg/m2, 17±4 months postpartum). We hypothesized that MSNA responses to apnea would be greater in PE relative to control subjects, that is, women 6-24 months following a healthy pregnancy and with no history of disordered pregnancies (HP; n=6, 31±6 y, BMI 29±5 kg/m2, 17±4 months postpartum). Integrated MSNA recordings were obtained at baseline and during a voluntary end-inspiratory apnea. Baseline mean arterial pressure (MAP; 87±10 vs 95±10 mmHg, P=0.2), total peripheral resistance (TPR; 13±3 vs 14±1 mmHg/L/min, P=0.4), and heart rate (HR; 74±5 vs 74±13, P=0.9) were similar in PE vs HP. Baseline MSNA was higher in PE compared to HP (26±9 vs 14±6 bursts/100heartbeats, P<0.01). The voluntary apnea was maintained for a similar duration in PE and HP (44±17 and 45±10 sec, P=0.9), without any difference in mean MAP (93±14 and 99±11, P=0.4), TPR (14±4 and 14±2, P=0.6), or HR (74±8 and 81±22, P=0.5) between groups. To discern between mild and moderate phases of chemoreflex stress, the apnea was divided into initial (i.e. first half) and latter (i.e. second half) phases for subsequent analyses. The initial phase of the apnea elicited a large increase in MSNA in the PE women which exceeded that observed in HP (37±13 vs 19±11, P=0.03, respectively). The peak sympathetic response observed in the latter half of the apnea was similar between PE and HP (56±21 vs 49±13 bursts/100hb, P=0.5). Thus, the sympathetic nervous system response to a mild chemoreflex stimulus is exaggerated in women who have had preeclampsia within the past 6-24 months relative to women without a history of preeclampsia. We have demonstrated that a recent history of preeclampsia is associated with chronic sympathetic activation as well as greater sympathetic reactivity. We propose these changes to the sympathetic nervous system contribute to the life-long risk for cardiovascular disease in formerly preeclamptic women. Funded by the Paul Titus Fellowship, Department of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Medicine
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Circulatory and Respiratory Physiology Commons, Reproductive and Urinary Physiology Commons
Sympathetic Nervous System Reactivity in Women Following Preeclamptic Pregnancies
Women who have had preeclamptic pregnancies are at risk for life-long cardiovascular disease. However, the factors contributing to this risk have yet to be established. Sympathetic nervous system dysregulation has been proposed to contribute to cardiovascular dysfunction during preeclamptic pregnancies. Therefore, we examined muscle sympathetic nerve activity (MSNA) at baseline and during a chemoreflex stimulus in women 6-24 months postpartum following a preeclamptic pregnancy (PE; n=6, age 28±2 y, BMI 27±3 kg/m2, 17±4 months postpartum). We hypothesized that MSNA responses to apnea would be greater in PE relative to control subjects, that is, women 6-24 months following a healthy pregnancy and with no history of disordered pregnancies (HP; n=6, 31±6 y, BMI 29±5 kg/m2, 17±4 months postpartum). Integrated MSNA recordings were obtained at baseline and during a voluntary end-inspiratory apnea. Baseline mean arterial pressure (MAP; 87±10 vs 95±10 mmHg, P=0.2), total peripheral resistance (TPR; 13±3 vs 14±1 mmHg/L/min, P=0.4), and heart rate (HR; 74±5 vs 74±13, P=0.9) were similar in PE vs HP. Baseline MSNA was higher in PE compared to HP (26±9 vs 14±6 bursts/100heartbeats, P<0.01). The voluntary apnea was maintained for a similar duration in PE and HP (44±17 and 45±10 sec, P=0.9), without any difference in mean MAP (93±14 and 99±11, P=0.4), TPR (14±4 and 14±2, P=0.6), or HR (74±8 and 81±22, P=0.5) between groups. To discern between mild and moderate phases of chemoreflex stress, the apnea was divided into initial (i.e. first half) and latter (i.e. second half) phases for subsequent analyses. The initial phase of the apnea elicited a large increase in MSNA in the PE women which exceeded that observed in HP (37±13 vs 19±11, P=0.03, respectively). The peak sympathetic response observed in the latter half of the apnea was similar between PE and HP (56±21 vs 49±13 bursts/100hb, P=0.5). Thus, the sympathetic nervous system response to a mild chemoreflex stimulus is exaggerated in women who have had preeclampsia within the past 6-24 months relative to women without a history of preeclampsia. We have demonstrated that a recent history of preeclampsia is associated with chronic sympathetic activation as well as greater sympathetic reactivity. We propose these changes to the sympathetic nervous system contribute to the life-long risk for cardiovascular disease in formerly preeclamptic women. Funded by the Paul Titus Fellowship, Department of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Medicine