Correlation of peripheral blood pressure with central blood pressure and estimation of central blood pressure thresholds for diagnosis of hypertension during pregnancy

Abstract

Objective: The main objective of the study was to evaluate the correlation and comparative use of peripheral blood pressure and central blood pressure (CBP) in identifying hypertension among pregnant women. Methods: A cross-sectional study was conducted at Nelson Mandela Academic Hospital from December 2022 to April 2024, involving 270 inpatients diagnosed with hypertensive disorders of pregnancy (HDP) and 270 normotensive controls in their second and third trimesters. Blood pressure measurements were obtained using the Microlife WatchBP Office Central, both at enrolment and within 7 days postpartum. A linear regression equation and a receiver operating characteristic curve (ROC) analysis were used to determine the thresholds for normal, mild, and severe CBP. Results: The ROC revealed that a central systolic blood pressure (cSBP) of 116 mm Hg or higher has a sensitivity of 78.5% and a specificity of 50.3% for diagnosing hypertension during pregnancy. Considering a normal peripheral diastolic pressure of less than 90 mm Hg, the upper limit of central diastolic blood pressure (cDBP) in normotensive controls was calculated to be 78 mm Hg. A significant positive correlation was found between peripheral systolic blood pressure (pSBP) and cSBP among normotensive and hypertensive women (p < 0.05). The median pSBP among patients with eclampsia with mild peripheral hypertension was 138.0 mmHg (IQR: 133.0-148.0) while the cSBP level in the same group was 145.0 mmHg (IQR: 140.0-150.0) mmHg. The overall median cSBP among women with eclampsia (n = 102) was 133.0 mmHg (IQR 120.0-143.0), and the median cDBP was 73.0 mmHg (IQR: 60.0-83.0), and these were significantly higher (p < 0.0001) than the median cSBP of 128.0 mmHg (IQR: 114.0-139) and cDBP of 71.0 mmHg (IQR: 61.0-81.0) among preeclamptic women. Conclusion: This study established the threshold values for central hypertension as 116/78 mmHg, with severe central hypertension defined as 148/95 mmHg or more. It reinforces the positive correlation between peripheral and CBP in both normotensive and hypertensive populations. CBP may serve as a better parameter for evaluating hypertension, especially in eclampsia. Further research is warranted to confirm these findings and to explore their clinical implications.