Heart Rate Variability and Cold Pressor Test before Onset of Pre-eclampsia in Pregnant Women-A Longitudinal Study

Introduction: A major obstetric complication, that leads to severe maternal and foetal morbidity is Pre-eclampsia (PE). Studies evaluating the autonomic nervous activity in pregnant women with PE shows conflicting results. Previous studies are inadequate for the identification of the most useful tools to detect and monitor autonomic dysfunction prior to PE. The cold pressor test is a simple and validated test, in which the afferent sensory pathways are stimulated by the cold stimulus, resulting in an increase in Blood Pressure (BP).

Aim: To evaluate the response to cold pressor test and Heart Rate Variability (HRV) to detect increased vascular reactivity and sympathetic activity prior to the clinical manifestation of PE in pregnant women.

Materials and Methods: A longitudinal study was conducted in in the Department of Physiology at Hamdard Institute of Medical Sciences, HAHC Hospital, Jamia Hamdard, New Delhi, India. The duration of the study was 11 months, from December 2018 to November 2019. Subjects were 50 pregnant women, between age 18-40 years and of 12-14 weeks of gestation. Cold pressor test and HRV were parameters measured for the assessment of the autonomic functions during 12 and 21 weeks of gestational period. The Statistical Package for Social Sciences (SPSS) version 26.0 was used for analysis of the quantitative data. Paired t-test was done for comparison of all values.

Results: The mean age of the study participants was 29±2.7 years. There was no hyper-reaction to cold pressor test at 12 weeks of gestation, nor the subjects showed any signs of PE. At 14 weeks of gestation, 2 (4%) showed hyper-reaction to cold pressor test. At 21 weeks of gestation, 3 (6%) subjects showed hyper-reactions to cold pressor test and out of them, 2 developed PE. Root Mean Square Standard Deviation (RMSSD) and difference between adjacent Standard Deviation of N-N intervals (SDNN) of HRV analysis were significantly higher in the first trimester as compared to 21 weeks of pregnancy.

Conclusion: Response to cold pressor test showed increased vascular reactivity, as a sign before the development of PE. HRV analysis could not detect any significant features of increased sympathetic activity prior to the clinical manifestation of PE in pregnant women.