Biomedical subjects

Ramón C Hermida

Publications and source records attributed to Ramón C Hermida.

At least 37 records · Page 2Linked to original sources

PubMed2004

Circadian time-qualified tolerance intervals for ambulatory blood pressure monitoring in the diagnosis of hypertension.

The large-amplitude circadian pattern in blood pressure of healthy subjects of both genders suggests that the constant threshold currently used to diagnose hypertension should be replaced by a time-specified reference limit reflecting the mostly predictable blood pressure variability during the 24 h. Accordingly, we derived circadian time-specified reference standards for blood pressure as a function of gender. We studied 743 normotensive Caucasian volunteers (400 men and 343 women), 45.7 +/- 16.5 (mean +/- SD) years of age. Blood pressure was measured by ambulatory monitoring at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours. Data from each blood pressure series were synchronized according to the rest-activity cycle of each individual in order to avoid differences among subjects in actual times of daily activity. Data were then used to compute 90% circadian tolerance intervals for each gender separately. 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 reflect expected changes in the tolerance limits as a function of gender and circadian sampling time, as well as upper blood pressure limits below the thresholds currently used for diagnosing hypertension, especially for women. The use of these time-dependent tolerance limits for the computation of a hyperbaric index as a measure of blood pressure excess has already been shown to provide a reproducible and high-sensitivity test for the diagnosis of hypertension, which can also be used to evaluate treatment efficacy.

Adult↗

PubMed2004

Administration-time-dependent effects of doxazosin GITS on ambulatory blood pressure of hypertensive subjects.

Previous studies have shown that a single nighttime dose of standard doxazosin, an alpha-adrenergic antagonist, reduces blood pressure (BP) throughout the 24 h. We investigated the administration-time-dependent effects of the new doxazosin gastrointestinal therapeutic system (GITS) formulation. We studied 91 subjects (49 men and 42 women), 56.7+/-11.2 (mean+/-SD) yrs of age with grade 1-2 essential hypertension; 39 patients had been previously untreated, and the remaining 52 had been treated with two antihypertensive medications with inadequate control of their hypertension. The subjects of the two groups, the monotherapy and polytherapy groups, respectively, were randomly assigned to receive the single daily dose of doxazosin GITS (4 mg/day) either upon awakening or at bedtime. BP was measured by ambulatory monitoring every 20 min during the day and every 30 min at night for 48 consecutive hours just before and after 3 months of treatment. After 3 months of doxazosin GITS therapy upon awakening, there was a small and nonstatistically significant reduction in BP (1.8 and 3.2mm Hg in the 24 h mean of systolic and diastolic BP in monotherapy; 2.2 and 1.9mm Hg in polytherapy), mainly because of absence of any effect on nocturnal BP. The 24 h mean BP reduction was larger and statistically significant (6.9 and 5.9 mm for systolic and diastolic BP, respectively, in monotherapy; 5.3 and 4.5 mm Hg in polytherapy) when doxazosin GITS was scheduled at bedtime. This BP-lowering effect was similar during both the day and nighttime hours. Doxazosin GITS ingested daily on awakening failed to provide full 24h therapeutic coverage. Bedtime dosing with doxazosin GITS, however, significantly reduced BP throughout the 24h both when used as a monotherapy and when used in combination with other antihypertensive pharmacotherapy. Knowledge of the chronopharmacology of doxazosin GITS is key to optimizing the efficiency of its BP-lowering effect, and this must be taken into consideration when prescribing this medication to patients.

Adrenergic alpha-Antagonists↗

PubMed2004

Comparison of parameters from rhythmometric models with multiple components on hybrid data.

Population multiple components is a statistical tool useful for the analysis of time-dependent hybrid data. With a small number of parameters, it is possible to model and to predict the periodic behavior of a population. In this article, we propose two methods to compare among populations rhythmometric parameters obtained by multiple component analysis. The first is a parametric method based in the usual statistical techniques for comparison of mean vectors in multivariate normal populations. The method, through MANOVA analysis, allows comparison of the MESOR and amplitude-acrophase pair of each component among two or more populations. The second is a nonparametric method, based in bootstrap techniques, to compare parameters from two populations. This test allows one to compare the MESOR, the amplitude, and the acrophase of each fitted component, as well as the global amplitude, orthophase, and bathyphase estimated when all fitted components are harmonics of a fundamental period. The idea is to calculate a confidence interval for the difference of the parameters of interest. If this interval does not contain zero, it can be concluded that the parameters from the two models are different with high probability. An estimation of p-value for the corresponding test can also be calculated. Both methods are illustrated with an example, based on clinical data. The nonparametric test can also be applied to paired data, a special situation of great interest in practice. By the use of similar bootstrap techniques, we illustrate how to construct confidence intervals for any rhythmometric parameter estimated from population multiple components models, including the orthophase, bathyphase, and global amplitude. These tests for comparison of parameters among populations are a needed tool when modeling the nonsinusoidal rhythmic behavior of hybrid data by population multiple component analysis.

Chronobiology Phenomena↗

PubMed2004

Reproducibility of the tolerance-hyperbaric test for diagnosing hypertension in pregnancy.

BACKGROUND: The tolerance-hyperbaric test has been shown to provide a valuable approach for the prediction of the outcome of pregnancy. In this test, diagnosis of hypertension is based on the hyperbaric index (area of blood pressure excess above the upper limit of a reference threshold) calculated by comparison with a time-specified tolerance interval for the circadian variability of blood pressure. OBJECTIVE: To evaluate prospectively the stability and reproducibility of the tolerance-hyperbaric test. METHODS: We studied 403 women who provided 2430 blood pressure series sampled for 48 consecutive hours once every 4 weeks from the first obstetric visit (mostly within the first trimester of gestation) until delivery. Circadian 90% tolerance limits for blood pressure were established as a function of trimester of gestation from 497 series previously sampled from an independent reference group of 189 normotensive pregnant women. Diagnosis of hypertension was established in this trial for each woman in the validation sample on the highly restricted basis of presenting at least one blood pressure profile with a hyperbaric index above the threshold for diagnosis after 20 weeks of gestation. RESULTS: Sensitivity of the tolerance-hyperbaric test was 93% for women sampled during the first trimester of gestation, and increased to 99% by the third trimester. Specificity was more than 99% in all trimesters. The positive and negative predictive values were greater than 96% in all trimesters. CONCLUSIONS: The tolerance-hyperbaric test represents a reproducible, stable, non-invasive and high-sensitivity test for the very early identification of subsequent hypertension in pregnancy.

Adult↗

PubMed2004

Effects of telmisartan 80 mg and valsartan 160 mg on ambulatory blood pressure in patients with essential hypertension.

OBJECTIVES: This trial investigated and compared the antihypertensive efficacy of telmisartan and valsartan, two angiotensin II receptor blockers, used in monotherapy at their maximum recommended dose in hypertensive patients. METHODS: We studied 70 subjects (32 men and 38 women) aged 47.6 +/- 12.2 (mean +/- SD) years, with mild to moderate essential hypertension; they were randomly assigned to receive monotherapy with either telmisartan (80 mg) or valsartan (160 mg), in the form of a single daily tablet upon awakening. Blood pressure was measured by ambulatory monitoring every 20 min during the day and every 30 min at night for 48 consecutive hours before and after 3 months of treatment. Physical activity was simultaneously monitored every minute by wrist actigraphy to calculate accurately the diurnal and nocturnal means of blood pressure on a per subject basis. RESULTS: There was a highly significant blood pressure reduction during the 24 h with both drugs. The blood pressure reduction in the 24-h mean was significantly larger for valsartan 160 mg (18.6 and 12.1 mmHg for systolic and diastolic blood pressure, respectively) than for telmisartan 80 mg (10.8 and 8.4 mmHg; P < 0.001 between treatment-groups). There was also a highly significant reduction (P < 0.001) of 6.5 mmHg in the 24-h mean of pulse pressure after valsartan administration only. The trough : peak ratio and the smoothness index were slightly higher in systolic, but similar in diastolic blood pressure, for telmisartan as compared to valsartan. CONCLUSIONS: Despite a shorter half-life, 160 mg/day valsartan was more effective in lowering blood pressure over 24 h than 80 mg/day telmisartan. Furthermore, valsartan was also more effective in lowering arterial pulse pressure, an observation that may have important therapeutic implications, given the mounting evidence that pulse pressure may be a risk factor for future cardiovascular events.

Administration, Oral↗

PubMed2004

Chronotherapy of hypertension.

PURPOSE OF REVIEW: Blood pressure displays appreciable predictable-in-time circadian variation. The chronotherapy of hypertension takes into account the clinically relevant features of the 24-h pattern of blood pressure, e.g. the accelerated morning rise and nighttime decline during sleep, plus potential administration circadian time determinants of the pharmacokinetics and dynamics of antihypertensive medications. RECENT FINDINGS: Significant administration-time differences in the kinetics (i.e. chronokinetics) plus the beneficial and adverse effects (termed chronodynamics) of antihypertensive drugs are well known. Thus, bedtime, but not morning, dosing with cilnidipine significantly reduces nocturnal blood pressure. In addition, the dose-response curve, therapeutic coverage, and efficacy of the doxazosin gastrointestinal therapeutic system are all markedly dependent on the circadian time of drug administration. Moreover, valsartan administration at bedtime as opposed to upon awakening results in improved diurnal/nocturnal blood pressure ratio, such that the dosing time of valsartan can be chosen in relation to the dipper status of any given patient to improve therapeutic benefit and reduce cardiovascular risk. SUMMARY: Nocturnal hypertension, which is characterized by the loss or even reversal of the expected 10-20% sleep-time blood-pressure decline, increases the risk of cardiac and cerebrovascular events. Chronotherapy provides a means of individualizing treatment of hypertension according to the circadian profile of blood pressure of each patient. The chronotherapeutic strategy constitutes a new option to optimize blood-pressure control and to reduce risk.

Antihypertensive Agents↗

PubMed2004

Effect of continuous positive airway pressure on ambulatory blood pressure in patients with obstructive sleep apnoea.

OBJECTIVES: Previous reports on the effects of continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea (OSA) on blood pressure has shown contradictory results. Accordingly, we have investigated the effects of CPAP on blood pressure and on the potential reversal of the diagnosis of hypertension in patients with OSA evaluated repeatedly by ambulatory blood pressure monitoring. METHODS: We studied 122 patients (104 men and 18 women), 55.1+/-10.5 years of age, with diagnosis of OSA corroborated by overnight polysomnography at the clinic. Among those patients, 83 were treated with CPAP after their first evaluation, while 39 remained without CPAP for the duration of the trial. Blood pressure was measured by ambulatory monitoring at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours, at baseline and after 2 and 4 months of intervention. RESULTS: There was a small, but not statistically significant, reduction in ambulatory blood pressure in patients treated with CPAP (0.7 and 1.5 mmHg in 24-h mean of systolic and diastolic blood pressure after 2 months of therapy; 2.0 and 2.3 mmHg after 4 months; P>0.239). The blood pressure reduction was very similar in patients with OSA followed for 4 months without CPAP (1.9 and 2.2 mmHg in 24-h mean of systolic and diastolic blood pressure, respectively; P=0.543). We found a high (77%) prevalence of hypertension among the patients participating in this study, although only 37% were receiving antihypertensive medication at the time of recruitment. The prevalence of hypertension was slightly but not significantly reduced to just 74% after 4 months of treatment with CPAP. CONCLUSIONS: The small reduction in blood pressure for consecutive profiles of ambulatory monitoring can probably be explained by the documented 'ABPM pressor effect' on patients using the ambulatory device for the first time. The high prevalence of hypertension among patients with OSA is not significantly reduced by treatment with CPAP. These results suggest that patients with OSA should always be properly evaluated for diagnosis of hypertension, and provided, if needed, with antihypertensive treatment apart from the recommended CPAP.

Blood Pressure↗

PubMed2004

Prognostic value of ambulatory blood pressure measurements for the diagnosis of hypertension in pregnancy.

Several studies have indicated that the use of the 24 h mean blood pressure, mainly using reference thresholds derived from general nonpregnancy practice, does not provide an effective test for an individualized early diagnosis of hypertension in pregnancy, thus concluding that ambulatory blood pressure monitoring is not a valid approach in pregnancy. With the use of ambulatory blood pressure monitoring, epidemiologic studies have reported gender differences in the circadian variability of blood pressure and heart rate. Typically, men exhibit a lower heart rate and higher blood pressure than women, the differences being larger for systolic than for diastolic blood pressure. Moreover, normotensive and hypertensive pregnant women are characterized by differing but predictable patterns of blood pressure variability throughout gestation. However, the diminished blood pressure in nongravid women as compared with men, the added decrease in blood pressure during the second trimester of gestation in normotensive but not in hypertensive pregnant women and the large amplitude of the circadian pattern that characterizes the blood pressure of healthy pregnant women at all gestational ages, have not been taken into account when establishing reference thresholds for the diagnosis of hypertension in pregnancy. This review will describe these issues, summarize previous results from independent groups on the prognostic value of ambulatory blood pressure monitoring in pregnancy, propose answers as to an accurate reference threshold for blood pressure at different stages of gestation and suggest how this information should be used in order to identify those women at a higher risk of hypertension, who will also be more suitable for prophylactic and/or therapeutic intervention in the early stages of pregnancy.

Blood Pressure↗

PubMed2003

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

Previous studies on ambulatory blood pressure monitoring as a potential screening test for hypertension in pregnancy have not carefully considered sampling requirements. We have examined the impact of duration and frequency of blood pressure sampling in the reproducibility of mean values in pregnancy. We analyzed 2430 blood pressure series sampled every 20 minutes during the day and every 30 minutes at night for 48 hours every 4 weeks from the first obstetric visit until delivery in 235 normotensive and 168 hypertensive pregnant women. Blood pressure series were decimated to generate shorter series with data sampled every 1, 2, 3, or 4 hours for 48 hours, as well as at the original rate for the first day. Reproducibility of mean blood pressure as well as sensitivity and specificity in the diagnosis of hypertension were compared between the original and the decimated series. Sensitivity and specificity of the 24-hour blood pressure mean are similar for the values calculated from the original series and for those obtained from shorter profiles up to data sampled every 3 hours but reduced by 5% to 12% when diagnosis is based on data sampled at 20- to 30-minute intervals for the first 24 hours. Results also indicate that the 24-hour blood pressure mean is better reproduced with data sampled at 3-hour intervals for 48 hours than by data sampled at 20- to 30-minute intervals for 1 day only. This study demonstrates that reproducibility of mean blood pressure values is more dependent on duration of sampling than on sampling rate.

Adolescent↗

PubMed2003

Administration time-dependent effects of valsartan on ambulatory blood pressure in hypertensive subjects.

This study investigated the administration time-dependent antihypertensive efficacy of valsartan, an angiotensin II receptor blocker. We studied 90 subjects (30 men and 60 women), 49.0+/-14.3 (mean+/-SD) years of age with stage 1 to 2 essential hypertension; they were randomly assigned to receive valsartan (160 mg/d) as a monotherapy either on awakening or at bedtime. Blood pressure was measured by ambulatory monitoring every 20 minutes during the day and every 30 minutes at night for 48 consecutive hours before and after 3 months of treatment. Physical activity was simultaneously monitored every minute by wrist actigraphy to accurately calculate the diurnal and nocturnal means of blood pressure on a per-subject basis. The highly significant blood pressure reduction after 3 months of treatment with valsartan (P<0.001) was similar for both treatment times (17.0 and 11.3 mm Hg reduction in the 24-hour mean of systolic and diastolic blood pressure with morning administration and 14.6 and 11.4 mm Hg reduction with bedtime administration; P>0.174 for treatment time effect). Valsartan administration at bedtime as opposed to on wakening resulted in a highly significant average increase by 6% (P<0.001) in the diurnal-nocturnal ratio of blood pressure; this corresponded to a 73% relative reduction in the number of nondipper patients. The findings confirm that valsartan efficiently reduces blood pressure throughout the entire 24 hours, independent of treatment time. They also suggest that time of treatment can be chosen according to the dipper status of a patient to optimize the effect of antihypertensive therapy, an issue that deserves further investigation.

Adult↗

PubMed2003

[Seasonal variation in plasma fibrinogen in dipper and non-dipper patients with mild-moderate essential hypertension].

BACKGROUND AND OBJECTIVE: Increased plasma fibrinogen is recognized as a significant parameter for assessing the potential risk of myocardial infarction and stroke. A seasonal variation has been reported for plasma fibrinogen, with highest values occurring in the coldest months of the year. On the other hand, the lack of nocturnal decline in blood pressure has been associated with an increase in cardiovascular events. Accordingly, we have quantified the yearly variation in plasma fibrinogen in hypertensive patients classified according to their nocturnal decline in blood pressure. PATIENTS AND METHOD: We studied 577 mild-to-moderate hypertensive patients (254 men), 53.8 13.8 years of age. Blood pressure was measured every 20 min during the day and every 30 min at night for 48 consecutive hours. Physical activity was simultaneously evaluated at 1-min intervals with a wrist actigraph. A complete blood test was performed on the same day before starting blood pressure monitoring. The circannual variation of plasma fibrinogen was established for all patients as well as for subgroups of dippers (n = 287) and non-dippers (n = 290; patients with a nocturnal blood pressure decline < 10% of the diurnal mean) by multiple-component analysis. RESULTS: For the whole group of hypertensive patients, plasma fibrinogen was characterized by a highly significant seasonal variation (p < 0.001), with a mean value of 324 mg/dl, double circannual amplitude (i.e, extent of predictable change along the year) of 75 mg/dl, and time of peak value on the first week of March. This circannual variation can be best represented by a model that includes components with periods of 12 and 6 months. The same model also characterized dippers as well as non-dippers, analyzed separately. Non-dippers showed higher plasma fibrinogen throughout the whole year as compared to dippers (p = 0.002). CONCLUSIONS: The elevation of plasma fibrinogen in non-dipper patients as compared to dippers could support the association between the lack of nocturnal decline in blood pressure with an increase in cardiovascular events, since the circannual variation in fibrinogen is timely correlated with the reported yearly variation in coronary events.

Adult↗

PubMed2003

[Administration-time dependent effects of acetyl-salicylic acid on blood pressure in patients with mild essential hypertension].

BACKGROUND AND OBJECTIVES: Previous studies on the potential influence of aspirin (AAS) on blood pressure have not taken in consideration the chronopharmacologic effects of non-steroidal antiinflammatory drugs. This pilot study investigated the effects of AAS on blood pressure in hypertensive patients under no antihypertensive treatment who received AAS at different day times according to their rest-activity cycle. PATIENTS AND METHOD: We studied 64 untreated patients with mild hypertension (24 men), 43.5 (12.0) (mean [SD]) years of age, randomly divided in 3 groups: group 1, non-pharmacological hygienic-dietetic recommendations; group 2, the same recommendations plus AAS (100 mg/day) on awakening, and group 3, the same recommendations plus AAS (100 mg/day) before bedtime. Blood pressure was measured every 20 min during the day and every 30 min at night for 48 consecutive hours before and after 3 months of intervention. The circadian pattern of blood pressure in each group was established by population multiple-component analysis. Circadian parameters obtained for each group of patients before and after the intervention were compared with a nonparametric paired test. RESULTS: After 3 months of non-pharmacological intervention, there was a small and non-significant reduction of blood pressure (< 1.5 mmHg; p = 0.28). There was no change in blood pressure when AAS was given on awakening (p = 0.21). A highly significant blood pressure reduction was, however, observed in patients who received AAS before bedtime (decrease of 7 and 5 mmHg in systolic and diastolic blood pressure, respectively; p = 0.006). CONCLUSIONS: Our results indicate a statistically significant time-dependent administration effect of low-dose AAS on blood pressure in untreated patients with mild hypertension. This effect reinforces the need to quantify and control AAS effects in patients using this agent in combination with antihypertensive agents.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2003

Administration time-dependent effects of aspirin on blood pressure in untreated hypertensive patients.

Previous studies on the potential influence of aspirin on blood pressure have not taken into consideration the chronopharmacological effects of nonsteroidal anti-inflammatory drugs. This pilot study investigates the effects of aspirin on blood pressure in untreated hypertensive patients who received aspirin at different times of the day according to their rest-activity cycle. We studied 100 untreated patients with mild hypertension (34 men and 66 women), 42.5+/-11.6 (mean+/-SD) years of age, randomly divided into 3 groups: nonpharmacological hygienic-dietary recommendations; the same recommendations and aspirin (100 mg/d) on awakening; or the same recommendations and aspirin before bedtime. Blood pressure was measured every 20 minutes during the day and every 30 minutes at night for 48 consecutive hours before and after 3 months of intervention. The circadian pattern of blood pressure in each group was established by population multiple-component analysis. After 3 months of nonpharmacological intervention, there was a small, nonsignificant reduction of blood pressure (<1.1 mm Hg; P>0.341). There was no change in blood pressure when aspirin was given on awakening (P=0.229). A highly significant blood pressure reduction was, however, observed in the patients who received aspirin before bedtime (decrease of 6 and 4 mm Hg in systolic and diastolic blood pressure, respectively; P<0.001). Results indicate a statistically significant administration time-dependent effect of low-dose aspirin on blood pressure in untreated patients with mild hypertension. The influence of aspirin on blood pressure demonstrated in this study indicates the need to quantify and control for aspirin effects in patients using this drug in combination with antihypertensive medication.

Adult↗

PubMed2003

[Circadian blood pressure variation in normal pregnancy, gestational hypertension, and preeclampsia].

BACKGROUND AND OBJECTIVE: Changes in circadian variation of blood pressure could be used either to predict preeclampsia or to assess its severity. With the objective of identifying potential differences in blood pressure at the early stages of pregnancy, we examined and compared the characteristics of circadian variability in blood pressure in healthy and complicated pregnant women who were systematically monitored throughout gestation. SUBJECTS AND METHOD: We analyzed 2,014 blood pressure series sampled through ambulatory monitoring for 48 hours once every 4 weeks from the first obstetric visit until delivery. The study included 205 women with uncomplicated pregnancy, 92 with gestational hypertension and 31 with preeclampsia. The circadian pattern of blood pressure variation for each group and trimester of gestation was established by means of a population multiple-components analysis. RESULTS: Differences in the 24-hour mean between healthy and complicated pregnancies were highly significant in all trimesters (p < 0.001), with values of 15.1 and 9.1 mmHg for systolic and diastolic blood presure, respectively, in the third trimester of pregnancy. The 24-hour mean of systolic/diastolic blood pressure for complicated pregnancies was always below 120/72 mmHg. Results further indicated similar circadian characteristics between gestational hypertension and preeclampsia in the first trimester of pregnancy. The difference between these two groups in the 24-hour mean was significant in the second trimester for systolic (3 mmHg; p = 0.002) but not diastolic blood pressure (0.9 mmHg; p = 0.230). In the third trimester, the difference between gestational hypertension and preeclampsia was significant for both variables (5.4 and 3.7 mmHg for systolic and diastolic blood pressure, respectively; p < 0.001). CONCLUSIONS: The differences in blood pressure between healthy and complicated pregnancies, which are observed as early as the first trimester of pregnancy, are detected when both systolic and diastolic blood pressure measurements in women with a late diagnosis of gestational hypertension or preeclampsia fall within accepted ranges of normotension. These differences offer new end points that may lead to an early identification of hypertensive complications in pregnancy as well as to the establishment of prophylactic interventions.

Adult↗

PubMed2003

Differences in circadian blood pressure variability during gestation between healthy and complicated pregnancies.

BACKGROUND: Changes in circadian variation of blood pressure (BP) could be used either to predict preeclampsia or to assess its severity. We examined and compared characteristics of circadian variability in BP in women with both healthy and complicated pregnancies who were systematically monitored throughout gestation. METHODS: We analyzed 2430 BP series sampled by ambulatory monitoring for 48 h once every 4 weeks from the first obstetric visit until delivery in 235 women with uncomplicated pregnancies, 128 with gestational hypertension, and 40 with preeclampsia. The circadian pattern of BP variation for each group and trimester of gestation was established by population multiple-components analysis. RESULTS: The differences in 24-h mean and amplitude between healthy and complicated pregnancies were highly significant in all trimesters (P < 0.001). Results further indicated similar circadian characteristics between gestational hypertension and preeclampsia in the first trimester of pregnancy. The difference between these two groups in 24-h mean was statistically significant for systolic (P =.002) and diastolic BP (P =.038) in the second trimester and, to a larger extent, in the third trimester (P < 0.001). CONCLUSIONS: The differences in BP between healthy and complicated pregnancies that can be observed as early as in the first trimester of pregnancy are found when both systolic and diastolic BP for women with a later diagnosis of gestational hypertension or preeclampsia are well within the accepted range of normotension. These differences offer new end points that may lead to an early identification of hypertensive complications in pregnancy as well as to the establishment of prophylactic intervention.

Adult↗

PubMed2003

Circadian rhythm of blood pressure challenges office values as the "gold standard" in the diagnosis of gestational hypertension.

Despite poor sensitivity and specificity, office blood pressure (BP) determinations are still the "gold standard" for diagnosing gestational hypertension. This prospective blind study evaluates the prognostic value of office values as compared with ambulatory monitoring in pregnancy. We analyzed 2175 BP series systematically sampled from 355 non-preeclamptic pregnant women for 48 h every 4 wks from the first hospital visit until delivery. Women were divided for comparative purposes into three groups: "detected" gestational hypertension, defined on the basis of casual clinical BP> 140/90 mmHg after 20 wks of gestation and hyperbaric index (area of BP excess above the upper limit of a time-specified tolerance interval adjusted for the circadian pattern of the reference population) consistently above the threshold for diagnosing hypertension in pregnancy; "undetected" gestational hypertension, women with office BP < 140/90 mmHg but hyperbaric index consistently above the threshold for diagnosis; and normotension, women with both office values and hyperbaric index below the respective thresholds for diagnosis. Small and insignificant differences in the 24h mean BP between "detected" and "undetected" gestational hypertension is observed in all trimesters, in contrast with highly significant differences between these two groups and normotensive pregnancies. Normotensive women are characterized by highly significant lesser incidence by 60% in preterm delivery, 70% in intrauterine growth retardation, and 50% in delivery by cesarean section (p < 0.001) compared with women with "detected" and "undetected" gestational hypertension (p > 0.715). In pregnancy, the hyperbaric index is markedly superior to office BP measurements for diagnosis of what should be truly considered gestational hypertension, and for prediction of the outcome of pregnancy.

Adult↗

PubMed2003

Methods for comparison of parameters from longitudinal rhythmometric models with multiple components.

Multiple components linear least-squares methods have been proposed for the detection of periodic components in nonsinusoidal longitudinal time series. However, a proper test for comparison of parameters obtained from this method for two or more time series is not yet available. Accordingly, we propose two methods, one parametric and one nonparametric, to compare parameters from rhythmometric models with multiple components. The parametric method is based on techniques commonly and generally employed in linear regression analysis. The comparison of parameters among two or more time series is accomplished by the use of so-called dummy variables. The nonparametric method is based on bootstrap techniques. This approach basically tests if the difference in any given parameter obtained by fitting a model with the same periods to two different longitudinal time series differs from zero. This method calculates a confidence interval for the difference in the tested parameter. If this interval does not contain zero, it can be concluded that the parameters obtained from the two time series are different with high probability. An estimation of the p-value for the corresponding test can also be calculated. By the use of similar bootstrap techniques, confidence intervals can also be obtained for any parameter derived from the multiple component fit of several periods to nonsinusoidal longitudinal time series, including the orthophase (peak time), bathyphase (trough time), and global amplitude (difference between the maximum and the minimum) of the fitted model waveform. These methods represent a valuable tool for the comparison of rhythm parameters obtained by multiple component analysis, and they render this approach as a generally applicable one for waveform representation and detection of periodicities in nonsinusoidal, sparse, and noisy longitudinal time series sampled with either equidistant or unequidistant observations.

Blood Pressure↗

PubMed2003

The 'ABPM effect' gradually decreases but does not disappear in successive sessions of ambulatory monitoring.

OBJECTIVES: Previous results have indicated that ambulatory monitoring provides a pressor effect on patients using the device for the first time, but not on successive sessions of monitoring. Our objective was to validate and quantify the extent and duration of this pressor effect in hypertensive patients repeatedly evaluated every few months. METHODS: We studied 823 mild-to-moderate hypertensive subjects (347 men), 53.4 +/- 14.1 years of age. Blood pressure was measured at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours, and physical activity was simultaneously evaluated every minute with a wrist actigraph. Forty per cent of the patients were evaluated twice or more. RESULTS: In patients evaluated for the first time, results indicated a highly statistically significant (P < 0.001) reduction during the second day of monitoring as compared to the first in the diurnal mean of systolic and diastolic blood pressure, but not in heart rate or physical activity. This pressor effect remained statistically significant for the first 10 h of monitoring, independent of gender, day of the week of monitoring, or number of antihypertensive drugs used by the patients. The nocturnal mean of blood pressure was, however, similar between both days of sampling. This 'ambulatory monitoring effect' was diminished, although not eliminated, in extent and duration for successive sessions of ambulatory monitoring. CONCLUSIONS: Ambulatory monitoring for 48 h revealed a statistically significant pressor response that could mostly reflect a novelty effect in the use of the monitoring device. This effect has marked implications in both research and clinical daily practice for a proper diagnosis of hypertension and evaluation of treatment efficacy by the use of ambulatory monitoring.

Adolescent↗