Concordance Between the Systolic Foot-to-Apex Interval and the Auscultatory Method for Measuring Brachial Systolic Pressure in Pregnant Women With or Without Blood Pressure Disorders and Search for Markers of Arterial Stiffness in Pre-eclampsia.

During pregnancy, high blood pressure remains the leading cause of maternal and foetal morbidity and mortality due to its complications and affects 5 to 10% of pregnancies. Hypertension in pregnancy is based on measurements taken in a medical setting and is defined by a systolic blood pressure ≥ 140 mmHg and/or a diastolic ≥ 90 mmHg. Regular monitoring of blood pressure is therefore recommended during pregnancy.

However, the main difficulty lies in the unreliability of many measuring devices. One of the hypotheses that may explain this unreliability is that they are based on the analysis of the oscillometric curve. The latter is influenced by the behaviour of the arterial wall and its biomechanical properties. However, during normal pregnancy, arterial compliance is altered, particularly as a result of hypervolaemia. With hypertension and pre-eclampsia, these changes are even more pronounced.

The gold standard for measuring blood pressure remains the auscultatory method based on the detection of Korotkoff's sounds. Now, this method is being used less and less in favour of the oscillometric method and increasing use of automated devices.However, these automatons use algorithms that are neither revealed nor interchangeable and, despite them being CE marked, the majority of the devices on the market have not been validated by clinical trials in accordance with the recommendations. Validating them in pregnant women is even more problematic and it is generally accepted that most voltage measurement systems can be faulty. To improve the accuracy and reproducibility of the oscillometric method, we have developed a new algorithm for determining systolic blood pressure based on the oscillometric curve, involving a temporal analysis of the oscillometric curve, not its envelope. This original approach has made it possible to highlight an increase in the delay between the foot and the peak of the systolic peak of the oscillogram (SFATI - Systolic Foot-to-Apex Time Interval), the maximum value of which coincides with the first Korotkoff sound, thus allowing real measurement of systolic blood pressure for the first time, not just a calculation.

In addition, this parameter presents a second elevation, observed in the region of mean blood pressure in patients with cardiovascular risk factors and therefore at a risk of increased arterial stiffness. This parameter should make it possible to easily identify subjects with an arterial compliance disorder via a simple standard blood pressure measurement. This opens up many possibilities in terms of screening including on a large scale and repeated basis.

Thus, with a simple blood pressure measurement, the SFATI algorithm should make it possible to correct the inconsistencies observed with the conventional oscillometric method during pregnancy, with two advantages :

• precise, reliable blood pressure measurement ensuring not only the diagnosis of pre-eclampsia but also the quality of monitoring, which is a prerequisite for appropriate therapeutic management;
• evaluation of the vessel walls, by detecting possible stiffness, indicating arterial damage. The aim here is to characterise the curve profile obtained in women with pre-eclampsia, at various levels of severity and also to evaluate this profile in women with a history of pre-eclampsia or at risk of pre-eclampsia. The possible specificities would then make it possible to integrate this approach into the current screening strategy in order to evaluate its interest on a larger scale.

We therefore make the following assumptions :

• the SFATI method is more reliable than the standard auscultatory method for accurately measuring brachial systolic blood pressure in pregnant women, whatever their blood pressure status;
• in women with blood pressure disorders, the oscillometric curve is modified with the presence of arterial stiffness markers, making it possible to characterise a particular oscillometric profile.
• this particular profile appears at an early stage and should make it possible to identify women at higher risk of developing pre-eclampsia.

Inclusion criteria

• Patient monitored for a single pregnancy in consultation or hospitalized in the department of Gynecology-Obstetrics at Nîmes University Hospital.
• Patient has given written informed consent.
• Patient has signed the consent form.
• Patient is covered by a health insurance scheme.
• Patient is aged over 18.

Exclusion criteria

• Multiple pregnancy.
• Patient is taking part in a category 1 research study.
• Patient is in a period of exclusion determined by another study.
• Patient is under legal protection or curatorship.
• Patient is in no condition to express her consent.
• Patient for whom it is impossible to give clear information.