Case report of an acceptable average but overswinging blood pressure in Circadian Hyper-Amplitude Tension, CHAT

Objectives. Blood pressure of pregnant women was measured around the clock at different gestational ages to obtain reference values and to examine whether women on the path to gestational hypertension and/or pre-eclampsia differed from uncomplicated pregnancies. Design. Observational study. Setting. A health maintenance organization in Minnesota. Results. Even when the 24-hour blood pressure average is within acceptable limits, an excessive circadian amplitude constitutes a harbinger of risk warranting attention and the institution of preventive measures. In one case reviewed herein, failure to do so led 8 weeks later to severe pre-eclampsia necessitating premature delivery and hospitalization of the infant for most of the first 26 months of life. Analyses of vital signs reported in the hospital chart reveal the expression of prominent about-weekly and about-monthly changes in early extrauterine life and the development of a circadian variation, already demonstrable at the time of birth, albeit with a small amplitude. On a group basis, MESOR differences of the order of 8 mm Hg are found between complicated and uncomplicated pregnancies well within the range of currently acceptable values. Conclusions. Time-specified reference limits, derived as 90% confidence limits from around-the-clock records of clinically healthy women in each trimester of pregnancy, are more sensitive than the currently used fixed thresholds to detect risk elevation. Such reference standards are also useful to detect abnormal blood pressure patterns. The danger associated with an excessive circadian blood pressure amplitude illustrated in a case report is fully supported by clinical outcome studies on 297 and 424 patients, respectively.