Abstract

Gestational hypertension (GH) is one of the pathologies leading to maternal-fetal morbidity and mortality worldwide. It is defined as an increase in blood pressure figures over 140/90 mmHg from the 20th week of gestation and can progress to more serious conditions such as preeclampsia and eclampsia. Although there is a well-defined treatment to control this pathology, the mechanisms underlying this disease are not very clear. The study of autonomic nervous activity has gained relevance in that the sympathetic system is attributed a predominant role in the pathophysiology of the phenomenon. Previous studies have shown a state of sympathoexcitation during normal pregnancy, which does not translate into an increase in blood pressure, while GH does show an increase in blood pressure values. The study of GH has been focused on the analysis of amplitudes and frequencies. This information allows us to characterize the behavior of the acquired signals but not to know the dynamics of the interaction between the different systems. The study of cardiovascular, nervous, and respiratory fluctuations provides valuable information about the control mechanisms that govern the systems, and one way to evaluate it is through synchronization analysis using a phase synchronization approach. Through this method, it is possible to evaluate not only the correlation but also to establish interrelationships between the systems under study to determine whether or not they are coupled, that is, the activity of one affects the other. This study was conducted in collaboration with the University of Alberta, Canada. Continuous blood pressure (BP), electrocardiogram (ECG), muscle sympathetic nerve activity (MSNA), and ECG-derived respiratory waveform signals from a group of 10 normotensive pregnant women, 10 hypertensive pregnant women, and 10 normotensive nonpregnant women on their third trimester. The recordings were made during 3 minutes of rest and 3 minutes of the cold pressor test. For the extraction of the phases and considering the non-linear nature of the signals, a continuous wavelet transform was used. Wavelet phase coherence was used to calculate the phase synchronization through the correlation of these at each frequency. Matlab was used for program and calculations. The results showed an increased parasympathetic modulation in the group of normotensive pregnant women compared to the hypertensive ones between the variables MSNA-BP, MSNA-RR, and MSNA-RESP, which would explain the effective control of blood pressure when faced with a stimulus such as CPT. An increase in respiration-driven vagal modulation could indicate functional changes at the central level between the ventral respiratory group and the rostral ventrolateral medulla. More research is needed to evaluate central nervous changes during pregnancy.