Time-Qualified Reference Values for Ambulatory Blood Pressure Monitoring in Pregnancy

Abstract

Abstract-To recognize the highly statistically significant circadian variability of blood pressure in pregnancy is to admit that the diagnosis of gestational hypertension or preeclampsia should be based not just on whether a casual blood pressure value is too high or too low, but rather on more pertinent questions: How long is blood pressure elevated above a given time-varying threshold? What is the excess blood pressure? When does most of the excess occur? Answers to these questions may be obtained by establishing (1) an adequate reference threshold for blood pressure and (2) a proper measurement of blood pressure elevation. Accordingly, we derived time-specified reference standards for blood pressure as a function of gestational age. We analyzed 1408 blood pressure series systematically sampled by ambulatory monitoring for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 235 women with uncomplicated pregnancies. Data from each blood pressure series were synchronized according to the rest-activity cycle of each individual to avoid differences among women in actual times of daily activity. Data were then used to compute 90% circadian tolerance intervals for each trimester of pregnancy, in keeping with the trends in blood pressure along gestation previously documented. The method, derived on the basis of bootstrap techniques, does not need to assume normality or symmetry in the data, and therefore, it is highly appropriate to describe the circadian pattern of blood pressure variability. Results not only reflect expected changes in the tolerance limits as a function of gestational age, but also upper limits markedly below the thresholds currently used for diagnosing hypertension in pregnancy. The use of these time-qualified tolerance limits for the computation of a hyperbaric index as a measure of BP excess has already been show to provide high sensitivity and specificity in the early identification of gestational hypertension and preeclampsia. Key Words: blood pressure Ⅲ heart rate Ⅲ pregnancy Ⅲ circadian Ⅲ blood pressure monitoring, ambulatory T he construction of time-specified reference limits requires systematic sampling in clinical health, in particular for those variables that are characterized by circadian rhythms of large amplitude, as is the case for blood pressure (BP). To date, BP determined casually in the examiner's office has been commonly used to diagnose hypertension and evaluate treatment efficacy. 1 These conventional timeunspecified single measurements may be misleading because BP and heart rate (HR) vary according to a spectrum of rhythms with several frequencies (the circadian in particular) and because measurements may be influenced by a host of internal factors, such as autonomic nervous system tone, vasoactive hormones, and hematologic and renal variables, plus a variety of external factors, including ambient temperature/humidity, physical activity, emotional state, alcohol/ caffeine consumption, meal comp...

Sampling requirements for ambulatory blood pressure monitoring in the diagnosis of hypertension in pregnancy

“…While all these studies are based on ABPM done for 24 hours only, the most extended conclusion so far is that due to poor results in the diagnostic test based on the BP mean, ABPM does not provide a proper approach for the early identification of preeclampsia, and it should not be used in pregnancy. 11 Against the common approach of relying on the 24-hour mean of ABPM, the combined approach of establishing tolerance intervals for the circadian variability of BP as a function of gestational age 25 and then computing the hyperbaric index (area of BP excess above the upper limit of the tolerance interval) by comparison of any patient's BP profile with those intervals, has been shown to provide high sensitivity and specificity for the early detection of pregnant women who will have subsequent development of gestational hypertension or preeclampsia 12 as well as a proper approach for the prediction of the outcome of pregnancy. 26 Results from this trial on the impact of the duration and frequency of BP sampling on the reproducibility of mean values indicate that parameters calculated from the ABPM profile are much more dependent on duration of sampling than on sampling rate.…”

“…23 Although most studies assessing the circadian BP profile have used 24-hour ABPM, as a compromise with practicality, monitoring over at least 48 hours has been shown to present advantages in the analysis of BP variability, 23,39 diagnosis of disease, 12,40 and evaluation of a patient's response to treatment. 39,40 The individualized estimation of rhythm characteristics become more reliable; new end points are obtained, such as the circadian period, which cannot usually be estimated from 24-hour records. 41 Previous findings suggested that ABPM done only for 24 hours may be too short to characterize accurately the features of the day-night variation in BP, including the precise period of that variation.…”

“…Gestational hypertension was defined as conventional BP values Ͼ140 or 90 mm Hg for systolic (SBP) or diastolic BP (DBP), respectively, after the 20th week of gestation, and/or a hyperbaric index (area of BP excess above the upper limit of a time-varying tolerance interval 25,26 ) consistently above the threshold for diagnosis of hypertension in pregnancy 12 after the 20th week of gestation for further corroboration. Preeclampsia was defined as gestational hypertension and proteinuria Ͼ300 mg in 24 hours of urine collection.…”

Seasonal Variation of Fibrinogen in Dipper and Nondipper Hypertensive Patients

“…As a compromise with practicability, monitoring over at least 48 hour has been shown to present advantages in the analysis of BP variability, 30 diagnosis of disease, 31 and evaluation of a patient's response to treatment. 30,31 Previous findings suggested that ABPM done only for 24 hour may be too short to characterize accurately the features of the day/night variation in BP, including the precise period of that variation. Along these lines, it has been recently demonstrated that, in patients evaluated by ABPM for the first time, there is a highly significant reduction during the second day of monitoring as compared with the first in the diurnal mean of BP.…”

Seguimiento farmacoterapéutico en farmacia comunitaria mediante monitorización ambulatoria de la presión arterial

“…Los individuos con patrón non dipper presentan un perfil de RCV y de lesiones en órganos diana más desfavorable que aquellos que presentan un perfil dipper. El patrón extreme-dipper, favorece la posibilidad que ocurra un ictus hemorrágico [3].…”