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Differences in wrist activity between dominant and non-dominant arms in subjects under ambulatory blood pressure monitoring
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AJH–April 2002–VOL. 15, NO. 4, PART 2
POSTERS: Blood Pressure Measurement/Monitoring
ters. The positive and negative predictive values were above 96% in all trimesters. The test provided, on the average, an early identification of gestational hypertension and preeclampsia 22.7 weeks prior to the clinical confirmation of the disease. Results fully corroborate previous studies on the diagnostic value of the THT [Hermida et al. Hypertension. 1998;31:83-89]. This approach, validated prospectively in one of the most extensive and systematic studies of ABPM in pregnancy, represents a reproducible, noninvasive, and high sensitivity test for the very early identification of subsequent gestational hypertension and preeclampsia.
P-130 SAMPLING REQUIREMENTS FOR AMBULATORY BLOOD PRESSURE MONITORING IN THE DIAGNOSIS OF HYPERTENSION IN PREGNANCY
SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, Tolerance-Hyperbaric Test, Preeclampsia
P-129 DIURNAL, NOCTURNAL OR 24-HOUR MEAN BLOOD PRESSURE VALUES FOR THE DIAGNOSIS OF GESTATIONAL HYPERTENSION. WHICH SHOULD BE USED? Diana E. Ayala, Ramon C. Hermida, Jose R. Fernandez, Artemio Mojon, Ignacio Alonso, Maria F. Aguilar, Rafael Ucieda, Manuel Iglesias. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain; Obstetrics & Gynecology Dept., Hospital Clinico Universitario, Santiago, Spain. Conventional office blood pressure (BP) measurements perform poorly, even in the third trimester of pregnancy, in selection of a population for potential detection of preeclampsia. The use of ambulatory BP monitoring (ABPM) has provided a method of BP assessment in pregnancy that compensates for some of the limitations of casual measurements. The most common approach is still to rely for diagnosis on the average of all values determined by ABPM. Here we aimed to examine and compare prospectively the effectiveness of the nocturnal, diurnal, and 24-hour means of BP as potential screening tests for the diagnosis of gestational hypertension and preeclampsia. We analyzed 2430 BP series obtained from 235 women with uncomplicated pregnancies and 168 who developed gestational hypertension or preeclampsia. BP was measured at 20-minute intervals during the day (07:00 to 23:00 hours) and at 30minute intervals at night for 48 consecutive hours once every 4 weeks from the first obstetric visit (mostly before 14 weeks of gestation) until delivery. Sensitivity and specificity are based on comparison of distributions of BP parameters with reference thresholds previously established from an independent population of 113 pregnant women [Hermida & Ayala. Hypertension. 1997;30:1531-1537]. Sensitivity of the 24-hour mean, always above 70%, was much higher than that obtained from casual BP measurements on the same women, always below 14%. The poorer results were consistently obtained for the nocturnal BP mean, with an average loss of 25% in sensitivity as compared to the daily or to the 24-hour BP mean. Sensitivity was similar for the daily and diurnal means, with values ranging from 71% for diastolic BP in the second trimester of pregnancy to 91% for systolic BP in the third. For the reference values of 111/110/114 mm Hg for the 24-hour mean of systolic BP in each of the three trimesters, the positive predictive value was always above 88%. Nocturnal BP values do not add valuable information for the diagnosis of hypertension in pregnancy. High sensitivity and positive predictive values for the diurnal BP mean suggest the potential cost-effectiveness of self-measurement for screening in pregnancy, an issue that deserves further investigation. SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, Gestational Hypertension, Preeclampsia
Ramon C. Hermida, Diana E. Ayala. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain. Several studies have investigated the potential use of mean blood pressure (BP) values derived from ambulatory BP monitoring (ABPM) as a screening test for hypertension in pregnancy. Most studies have been based on data sampled at 15 to 30-minute intervals for 24 hours. Sampling requirements for BP, however, have not yet been carefully taken into consideration. We have examined the impact of duration and frequency of BP sampling in the reproducibility of mean BP values. We analyzed 2430 BP series obtained from 235 women with uncomplicated pregnancies and 168 who developed gestational hypertension or preeclampsia. BP was measured at 20-minute intervals during the day (07:00 to 23:00 hours) and at 30-minute intervals at night for 48 consecutive hours once every 4 weeks from the first obstetric visit (mostly before 14 weeks of gestation) until delivery. BP series were decimated to generate shorter series with data sampled at 1, 2, 3, or 4-hour intervals for 48 hours, as well as at the original rate for just the first 24 hours. Reproducibility of mean BP as well as sensitivity and specificity in the diagnosis of hypertension in pregnancy were compared between the original and the decimated BP series. Sensitivity and specificity of the 24-hour, diurnal and nocturnal means of systolic and diastolic BP are similar for the values calculated from the original series and those obtained from shorter series up to data obtained at 3-hour intervals. For all the parameters, sensitivity and specificity are reduced by 5-15% when diagnosis was based on data sampled at 20-30 minute intervals for the first 24 hours. Bland-Altman plots indicate that the BP mean from the original series are better reproduced with data sampled at 3-hour intervals for 48 hours than by data sampled at 20-30 minute intervals for just one day. This study on women systematically studied by ABPM throughout gestation corroborates that reproducibility of mean BP values is more dependent on duration of sampling than on sampling rate. Thus, sampling requirements can be greatly reduced by expanding the monitoring span to at least 2 consecutive days. Results further indicate that ABPM for 24 hours may be insufficient for a proper diagnosis of hypertension in pregnancy. SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Sampling Requirements, Gestational Hypertension, Ambulatory Blood Pressure Monitoring
P-131 DIFFERENCES IN WRIST ACTIVITY BETWEEN DOMINANT AND NON-DOMINANT ARMS IN SUBJECTS UNDER AMBULATORY BLOOD PRESSURE MONITORING Ramon C. Hermida, Jose R. Fernandez, Artemio Mojon, Ignacio Alonso, Diana E. Ayala. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain. Wrist activity has been frequently used for automatic sleep/wake identification, providing results highly correlated with those from polysomnography [Cole et al. Sleep. 1992;15:461-469]. While studies on the differences in activity between dominant and non-dominant arms show contradictory results, there is no information available on the potential effects of simultaneous ambulatory blood pressure (BP) monitoring (ABPM) on wrist activity. Thus, there is not yet agreement on where to record motor activity on patients who are evaluated by ABPM. The purpose of this study was to evaluate the differences in activity between dominant and non-dominant arms in subjects wearing an ABPM device. We studied 51 clinically healthy normotensive volunteers (24 men) and 23 patients (10 men) with mild untreated hypertension, 23.7⫾6.3
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AJH–April 2002–VOL. 15, NO. 4, PART 2
(mean⫾SD) years of age. BP was measured at the non-dominant arm every 20 minutes during the day and every 30 minutes at night for 48 consecutive hours, and physical activity was simultaneously recorded at 1-minute intervals with a wrist actigraph at each arm. In keeping with previous studies on this area, we used for analysis the mean activity for the 5 minutes prior to each BP reading. The circadian variability in activity at each arm as well as in the difference in activity between arms was established by population-multiple component analysis [Fernandez & Hermida. Chronobiol Int. 1998;15:191-204]. For both normotensive as well as mild hypertensive subjects, the difference in activity between the dominant and non-dominant arms shows a highly significant circadian variation (P⬍0.001), with a crest time at 7 hours after awakening from nocturnal sleep and a double circadian amplitude (extent of predictable change along the 24 hours) of 24 counts/minute (18% of the daily mean activity). As a consequence, there is a significant difference in amplitude, but not in 24-hour mean (P⫽0.178), between activity measured at the dominant and non-dominant arms. Results indicate that the non-dominant arm shows a lower activity during the day, possible because patients are instructed to keep the arm still during BP measurement. During nocturnal resting hours, the non-dominant arm shows higher activity that the dominant arm, possible due to the discomfort and moderate sleep disturbances of ABPM. Accordingly, the dominant arm should be preferred to register wrist activity in patients wearing an ABPM device at the nondominant arm.
or successive times 3 months apart. ABPM for 48 consecutive hours in normotensive subjects reveals a statistically significant pressor response that could reflect a novelty effect in the use of the monitoring device for the first time, and that cannot be due just to regression to the mean. This “ABPM effect”, much higher in hypertensive patients [Hermida et al. Am J Hypertens. 2001;14:34], should be taken into consideration for a proper diagnosis of hypertension and evaluation of treatment efficacy by the use of ABPM.
SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, Wrist Activity, Mild Hypertension
P-132 PRESSOR RESPONSE TO AMBULATORY BLOOD PRESSURE MONITORING IN NORMOTENSIVE SUBJECTS Ramon C. Hermida, Diana E. Ayala, Jose R. Fernandez, Artemio Mojon, Ignacio Alonso, Carlos Calvo. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain; Hypertension and Vascular Risk Unit, Hospital Clinico Universitario, Santiago, Spain. The use of ambulatory blood pressure (BP) monitoring (ABPM) has provided a method of BP assessment that compensates for some of the limitations of conventional office values. Elimination of the “white-coat” effect is among the described advantages of ABPM. However, differences between consecutive days of monitoring in patients wearing the device for the first but not for the second and successive times [Hermida et al. Am J Hypertens. 2001;14:34], suggest a pressor response to ABPM. We have evaluated the extent and duration of this “ABPM effect” in normotensive subjects. We studied 170 volunteers (117 men), 23.2⫾3.7 (mean⫾SD) years of age, without medical history of hypertension and diurnal BP mean from ABPM consistently below 135/85 for systolic/ diastolic BP. Subjects underwent ABPM at 30-minute intervals for 48 consecutive hours in up to six different occasions within 2 years, yielding 515 BP profiles. Circadian parameters established by population multiple-component analysis [Fernandez & Hermida. Chronobiol Int. 1998; 15:191-204] were compared among consecutive days of monitoring by nonparametric testing. In normotensive volunteers evaluated for the first time, results indicate a highly significant (P⬍0.001) reduction during the second day of monitoring as compared to the first in the diurnal, but not in the nocturnal mean, of systolic and diastolic BP. This pressor effect increases BP on the average by a significant 4 and 3 mm Hg for systolic and diastolic BP for the first 4 hours of measurement. This effect can be documented as statistically significant independently of gender or day of the week of monitoring. The pressor effect was almost double in subjects who started ABPM in the evening (after 13:00 hours) as compared to subjects who started monitoring in the morning. This “ABPM effect” cannot be observed when the same subjects were evaluated for the second
SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, ABPM Effect, Normotension
P-133 DIFFERENCES IN THE CIRCADIAN VARIATION OF BLOOD PRESSURE BETWEEN NORMOTENSIVE AND WHITE COAT HYPERTENSIVE SUBJECTS Ramon C. Hermida, Carlos Calvo, Diana E. Ayala, Manuel Covelo, Maria J. Dominguez, Carmen Martinez, Jose E. Lopez. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain; Hypertension and Vascular Risk Unit, Hospital Clinico Universitario, Santiago, Spain. The prevalence and clinical significance of white coat hypertension (WCH) is still controversial. Although recent longitudinal studies have provided preliminary prognostic data on subjects with WCH as compared to patients with sustained hypertension, the possible relation between WCH and vascular risk is still under debate. Accordingly, we compared the circadian pattern of blood pressure (BP) variability between normotensive subjects and patients with WCH. We studied 186 subjects (85 mean), 49.5⫾14.7 (mean⫾SD) years of age, with diurnal BP mean below 135/85 for systolic/diastolic BP, and hyperbaric index (area of BP excess above a time-specified tolerance interval) below the previously established threshold for diagnosis of hypertension from data obtained by ambulatory BP monitoring [Hermida et al. Hypertension. 2000;35:118125]. Among those subjects, 94 (47 men) had WCH (mean from 6 office BP measurements above 140 or 90 mm Hg for systolic or diastolic BP). BP was measured at 20-minute intervals during the day (07:00 to 23:00 hours) and at 30-minute intervals at night for 48 consecutive hours. Circadian parameters established by population multiple-component analysis [Fernandez & Hermida. Chronobiol Int. 1998;15:191-204] were compared between normotensive and WCH subjects by nonparametric testing. Patients with WCH are characterize by a significant increase in systolic (3.1 mm Hg; P⬍0.001) but not in diastolic BP (P⫽0.452 for comparison of 24-hour mean) as compared to normotensive subjects. The differences in systolic BP between normotension and WCH are much more pronounced during the first 6 hours after awakening, and they are almost irrelevant during nocturnal resting hours. The largest and highly significant difference between groups was found around the clock in pulse pressure (about 4 mm Hg in 24-hour mean, P⬍0.001). In patients studied by 48-hour ambulatory monitoring, WCH is characterized by a significant elevation in systolic BP and, especially, in pulse pressure as compared to truly normotensive subjects. If indeed pulse pressure is an independent predictor of risk and cardiovascular events, WCH could then be associated to a long-term worst prognosis in comparison to true normotension, an issue that deserves further investigation. SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Pulse Pressure, Ambulatory Blood Pressure Monitoring, White Coat Hypertension
AJH–April 2002–VOL. 15, NO. 4, PART 2
POSTERS: Blood Pressure Measurement/Monitoring
ters. The positive and negative predictive values were above 96% in all trimesters. The test provided, on the average, an early identification of gestational hypertension and preeclampsia 22.7 weeks prior to the clinical confirmation of the disease. Results fully corroborate previous studies on the diagnostic value of the THT [Hermida et al. Hypertension. 1998;31:83-89]. This approach, validated prospectively in one of the most extensive and systematic studies of ABPM in pregnancy, represents a reproducible, noninvasive, and high sensitivity test for the very early identification of subsequent gestational hypertension and preeclampsia.
P-130 SAMPLING REQUIREMENTS FOR AMBULATORY BLOOD PRESSURE MONITORING IN THE DIAGNOSIS OF HYPERTENSION IN PREGNANCY
SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, Tolerance-Hyperbaric Test, Preeclampsia
P-129 DIURNAL, NOCTURNAL OR 24-HOUR MEAN BLOOD PRESSURE VALUES FOR THE DIAGNOSIS OF GESTATIONAL HYPERTENSION. WHICH SHOULD BE USED? Diana E. Ayala, Ramon C. Hermida, Jose R. Fernandez, Artemio Mojon, Ignacio Alonso, Maria F. Aguilar, Rafael Ucieda, Manuel Iglesias. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain; Obstetrics & Gynecology Dept., Hospital Clinico Universitario, Santiago, Spain. Conventional office blood pressure (BP) measurements perform poorly, even in the third trimester of pregnancy, in selection of a population for potential detection of preeclampsia. The use of ambulatory BP monitoring (ABPM) has provided a method of BP assessment in pregnancy that compensates for some of the limitations of casual measurements. The most common approach is still to rely for diagnosis on the average of all values determined by ABPM. Here we aimed to examine and compare prospectively the effectiveness of the nocturnal, diurnal, and 24-hour means of BP as potential screening tests for the diagnosis of gestational hypertension and preeclampsia. We analyzed 2430 BP series obtained from 235 women with uncomplicated pregnancies and 168 who developed gestational hypertension or preeclampsia. BP was measured at 20-minute intervals during the day (07:00 to 23:00 hours) and at 30minute intervals at night for 48 consecutive hours once every 4 weeks from the first obstetric visit (mostly before 14 weeks of gestation) until delivery. Sensitivity and specificity are based on comparison of distributions of BP parameters with reference thresholds previously established from an independent population of 113 pregnant women [Hermida & Ayala. Hypertension. 1997;30:1531-1537]. Sensitivity of the 24-hour mean, always above 70%, was much higher than that obtained from casual BP measurements on the same women, always below 14%. The poorer results were consistently obtained for the nocturnal BP mean, with an average loss of 25% in sensitivity as compared to the daily or to the 24-hour BP mean. Sensitivity was similar for the daily and diurnal means, with values ranging from 71% for diastolic BP in the second trimester of pregnancy to 91% for systolic BP in the third. For the reference values of 111/110/114 mm Hg for the 24-hour mean of systolic BP in each of the three trimesters, the positive predictive value was always above 88%. Nocturnal BP values do not add valuable information for the diagnosis of hypertension in pregnancy. High sensitivity and positive predictive values for the diurnal BP mean suggest the potential cost-effectiveness of self-measurement for screening in pregnancy, an issue that deserves further investigation. SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, Gestational Hypertension, Preeclampsia
Ramon C. Hermida, Diana E. Ayala. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain. Several studies have investigated the potential use of mean blood pressure (BP) values derived from ambulatory BP monitoring (ABPM) as a screening test for hypertension in pregnancy. Most studies have been based on data sampled at 15 to 30-minute intervals for 24 hours. Sampling requirements for BP, however, have not yet been carefully taken into consideration. We have examined the impact of duration and frequency of BP sampling in the reproducibility of mean BP values. We analyzed 2430 BP series obtained from 235 women with uncomplicated pregnancies and 168 who developed gestational hypertension or preeclampsia. BP was measured at 20-minute intervals during the day (07:00 to 23:00 hours) and at 30-minute intervals at night for 48 consecutive hours once every 4 weeks from the first obstetric visit (mostly before 14 weeks of gestation) until delivery. BP series were decimated to generate shorter series with data sampled at 1, 2, 3, or 4-hour intervals for 48 hours, as well as at the original rate for just the first 24 hours. Reproducibility of mean BP as well as sensitivity and specificity in the diagnosis of hypertension in pregnancy were compared between the original and the decimated BP series. Sensitivity and specificity of the 24-hour, diurnal and nocturnal means of systolic and diastolic BP are similar for the values calculated from the original series and those obtained from shorter series up to data obtained at 3-hour intervals. For all the parameters, sensitivity and specificity are reduced by 5-15% when diagnosis was based on data sampled at 20-30 minute intervals for the first 24 hours. Bland-Altman plots indicate that the BP mean from the original series are better reproduced with data sampled at 3-hour intervals for 48 hours than by data sampled at 20-30 minute intervals for just one day. This study on women systematically studied by ABPM throughout gestation corroborates that reproducibility of mean BP values is more dependent on duration of sampling than on sampling rate. Thus, sampling requirements can be greatly reduced by expanding the monitoring span to at least 2 consecutive days. Results further indicate that ABPM for 24 hours may be insufficient for a proper diagnosis of hypertension in pregnancy. SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Sampling Requirements, Gestational Hypertension, Ambulatory Blood Pressure Monitoring
P-131 DIFFERENCES IN WRIST ACTIVITY BETWEEN DOMINANT AND NON-DOMINANT ARMS IN SUBJECTS UNDER AMBULATORY BLOOD PRESSURE MONITORING Ramon C. Hermida, Jose R. Fernandez, Artemio Mojon, Ignacio Alonso, Diana E. Ayala. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain. Wrist activity has been frequently used for automatic sleep/wake identification, providing results highly correlated with those from polysomnography [Cole et al. Sleep. 1992;15:461-469]. While studies on the differences in activity between dominant and non-dominant arms show contradictory results, there is no information available on the potential effects of simultaneous ambulatory blood pressure (BP) monitoring (ABPM) on wrist activity. Thus, there is not yet agreement on where to record motor activity on patients who are evaluated by ABPM. The purpose of this study was to evaluate the differences in activity between dominant and non-dominant arms in subjects wearing an ABPM device. We studied 51 clinically healthy normotensive volunteers (24 men) and 23 patients (10 men) with mild untreated hypertension, 23.7⫾6.3
78A
POSTERS: Blood Pressure Measurement/Monitoring
AJH–April 2002–VOL. 15, NO. 4, PART 2
(mean⫾SD) years of age. BP was measured at the non-dominant arm every 20 minutes during the day and every 30 minutes at night for 48 consecutive hours, and physical activity was simultaneously recorded at 1-minute intervals with a wrist actigraph at each arm. In keeping with previous studies on this area, we used for analysis the mean activity for the 5 minutes prior to each BP reading. The circadian variability in activity at each arm as well as in the difference in activity between arms was established by population-multiple component analysis [Fernandez & Hermida. Chronobiol Int. 1998;15:191-204]. For both normotensive as well as mild hypertensive subjects, the difference in activity between the dominant and non-dominant arms shows a highly significant circadian variation (P⬍0.001), with a crest time at 7 hours after awakening from nocturnal sleep and a double circadian amplitude (extent of predictable change along the 24 hours) of 24 counts/minute (18% of the daily mean activity). As a consequence, there is a significant difference in amplitude, but not in 24-hour mean (P⫽0.178), between activity measured at the dominant and non-dominant arms. Results indicate that the non-dominant arm shows a lower activity during the day, possible because patients are instructed to keep the arm still during BP measurement. During nocturnal resting hours, the non-dominant arm shows higher activity that the dominant arm, possible due to the discomfort and moderate sleep disturbances of ABPM. Accordingly, the dominant arm should be preferred to register wrist activity in patients wearing an ABPM device at the nondominant arm.
or successive times 3 months apart. ABPM for 48 consecutive hours in normotensive subjects reveals a statistically significant pressor response that could reflect a novelty effect in the use of the monitoring device for the first time, and that cannot be due just to regression to the mean. This “ABPM effect”, much higher in hypertensive patients [Hermida et al. Am J Hypertens. 2001;14:34], should be taken into consideration for a proper diagnosis of hypertension and evaluation of treatment efficacy by the use of ABPM.
SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, Wrist Activity, Mild Hypertension
P-132 PRESSOR RESPONSE TO AMBULATORY BLOOD PRESSURE MONITORING IN NORMOTENSIVE SUBJECTS Ramon C. Hermida, Diana E. Ayala, Jose R. Fernandez, Artemio Mojon, Ignacio Alonso, Carlos Calvo. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain; Hypertension and Vascular Risk Unit, Hospital Clinico Universitario, Santiago, Spain. The use of ambulatory blood pressure (BP) monitoring (ABPM) has provided a method of BP assessment that compensates for some of the limitations of conventional office values. Elimination of the “white-coat” effect is among the described advantages of ABPM. However, differences between consecutive days of monitoring in patients wearing the device for the first but not for the second and successive times [Hermida et al. Am J Hypertens. 2001;14:34], suggest a pressor response to ABPM. We have evaluated the extent and duration of this “ABPM effect” in normotensive subjects. We studied 170 volunteers (117 men), 23.2⫾3.7 (mean⫾SD) years of age, without medical history of hypertension and diurnal BP mean from ABPM consistently below 135/85 for systolic/ diastolic BP. Subjects underwent ABPM at 30-minute intervals for 48 consecutive hours in up to six different occasions within 2 years, yielding 515 BP profiles. Circadian parameters established by population multiple-component analysis [Fernandez & Hermida. Chronobiol Int. 1998; 15:191-204] were compared among consecutive days of monitoring by nonparametric testing. In normotensive volunteers evaluated for the first time, results indicate a highly significant (P⬍0.001) reduction during the second day of monitoring as compared to the first in the diurnal, but not in the nocturnal mean, of systolic and diastolic BP. This pressor effect increases BP on the average by a significant 4 and 3 mm Hg for systolic and diastolic BP for the first 4 hours of measurement. This effect can be documented as statistically significant independently of gender or day of the week of monitoring. The pressor effect was almost double in subjects who started ABPM in the evening (after 13:00 hours) as compared to subjects who started monitoring in the morning. This “ABPM effect” cannot be observed when the same subjects were evaluated for the second
SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Ambulatory Blood Pressure Monitoring, ABPM Effect, Normotension
P-133 DIFFERENCES IN THE CIRCADIAN VARIATION OF BLOOD PRESSURE BETWEEN NORMOTENSIVE AND WHITE COAT HYPERTENSIVE SUBJECTS Ramon C. Hermida, Carlos Calvo, Diana E. Ayala, Manuel Covelo, Maria J. Dominguez, Carmen Martinez, Jose E. Lopez. Bioengineering & Chronobiology Labs., University of Vigo, Vigo, Spain; Hypertension and Vascular Risk Unit, Hospital Clinico Universitario, Santiago, Spain. The prevalence and clinical significance of white coat hypertension (WCH) is still controversial. Although recent longitudinal studies have provided preliminary prognostic data on subjects with WCH as compared to patients with sustained hypertension, the possible relation between WCH and vascular risk is still under debate. Accordingly, we compared the circadian pattern of blood pressure (BP) variability between normotensive subjects and patients with WCH. We studied 186 subjects (85 mean), 49.5⫾14.7 (mean⫾SD) years of age, with diurnal BP mean below 135/85 for systolic/diastolic BP, and hyperbaric index (area of BP excess above a time-specified tolerance interval) below the previously established threshold for diagnosis of hypertension from data obtained by ambulatory BP monitoring [Hermida et al. Hypertension. 2000;35:118125]. Among those subjects, 94 (47 men) had WCH (mean from 6 office BP measurements above 140 or 90 mm Hg for systolic or diastolic BP). BP was measured at 20-minute intervals during the day (07:00 to 23:00 hours) and at 30-minute intervals at night for 48 consecutive hours. Circadian parameters established by population multiple-component analysis [Fernandez & Hermida. Chronobiol Int. 1998;15:191-204] were compared between normotensive and WCH subjects by nonparametric testing. Patients with WCH are characterize by a significant increase in systolic (3.1 mm Hg; P⬍0.001) but not in diastolic BP (P⫽0.452 for comparison of 24-hour mean) as compared to normotensive subjects. The differences in systolic BP between normotension and WCH are much more pronounced during the first 6 hours after awakening, and they are almost irrelevant during nocturnal resting hours. The largest and highly significant difference between groups was found around the clock in pulse pressure (about 4 mm Hg in 24-hour mean, P⬍0.001). In patients studied by 48-hour ambulatory monitoring, WCH is characterized by a significant elevation in systolic BP and, especially, in pulse pressure as compared to truly normotensive subjects. If indeed pulse pressure is an independent predictor of risk and cardiovascular events, WCH could then be associated to a long-term worst prognosis in comparison to true normotension, an issue that deserves further investigation. SUPPORT: DGES, PM98-0106; PGICT00-PXI-32205PN; University of Vigo. Key Words: Pulse Pressure, Ambulatory Blood Pressure Monitoring, White Coat Hypertension