Cumulative sums in quantifying circadian blood pressure patterns

Clinical information from repeated blood pressure measurements in the management of heart failure with preserved ejection fraction

It remains unclear whether cumulative blood pressure (BP) exposure is associated with adverse outcomes in heart failure with preserved ejection fraction (HFpEF). The aim was to investigate the associations of adverse health outcomes with cumulative BP exposure as captured by weighted BP, cumulative BP and trends in BP over a 1-year timespan from baseline to a 12-month visit among 1303 patients with HFpEF (49.5% women; mean age, 71.5 years) enrolled in the TOPCAT (Treatment of Preserved Cardiac Function Heart Failure with an Aldosterone Antagonist) trial. The primary endpoints consisted of death from cardiovascular causes, aborted cardiac arrest, or hospitalization for the management of heart failure.We computed hazard ratios with a 1-SD increase in weighted BP and cumulative BP. In the spironolactone group, compared with patients with a downward trend in BP, those with an upward trend had higher event rates. However, there were no differences in event rates between those with upward and downward trends in BP in the placebo group. In multivariable-adjusted analyses that additionally accounted for baseline BP, weighted systolic BP and cumulative systolic BP predicted (P ≤ 0.037) the primary composite endpoint (hazard ratio [HR], 1.21; 95% CI, 1.05-1.39/1.15; 1.01-1.31) and hospitalization for HF (1.29; 1.09-1.52/1.18; 1.02-1.37), respectively. Among patients aged ≤72 years, cumulative systolic BP increased (P ≤ 0.016) the risk of the primary endpoint and hospitalization for HF. Higher cumulative systolic BP exposure conferred a higher risk of the primary endpoint and hospitalization for HF, independent of baseline BP. Our findings underscore that longitudinal BP measurements may refine risk stratification for patients with HFpEF.

Biphasic changes in spontaneous cardiovagal baroreflex sensitivity during passive hyperthermia

Successful adaptation to passive hyperthermia requires continual adjustment of circulation, which is mediated mainly by the autonomic nervous system. The goal of this study was to explore the alterations in spontaneous cardiovagal baroreflex sensitivity (BRS) during exposure to a hot environment. To continuously follow changes in core body temperature (Tc), haemodynamics, and BRS, male Wistar-Kyoto rats were implanted with telemetric transmitters. BRS at an ambient temperature of 23 °C was not steady but oscillated with a maximum power in the range of 0.02–0.2 Hz. Exposure to hot air immediately shifted the distribution of BRS to higher values, although Tc remained unchanged (37.2 (0.3) °C), and the average BRS changed from 1.3 (0.3) to 3 (1.4) ms.mmHg⁻¹, p < 0.0001. The degree of initial cardiovagal baroreflex sensitization explained 57% of the variability in the time to the onset of arterial pressure decline (p = 0.0114). With an increasing Tc (>38.8 (0.6) °C), BRS non-linearly declined, but haemodynamic parameters remained stable even above a Tc of 42 °C when the cardiovagal baroreflex was virtually non-operative. Abrupt full desensitization of the cardiovagal baroreflex with a muscarinic blocker did not induce arterial pressure decline. Our data indicate that a progressive decrease in BRS during passive hyperthermia does not induce haemodynamic instability. The positive association between initial cardiovagal baroreflex sensitization and the time to the onset of arterial pressure decline may reflect the potential protective role of parasympathetic activation during exposure to a hot environment.

Lactobacillus rhamnosus GG conditioned media modulates acute reactive oxygen species and nitric oxide in J774 murine macrophages

Phagocytes such as macrophages are capable of detecting and killing pathogenic bacteria by producing reactive oxygen and nitrogen species. Formation of free radicals in macrophages may be regulated by probiotics or by factors released by probiotics but yet to be identified. Thus, studies were carried out to determine whether cell-free conditioned medium obtained from cultures of Lactobacillus rhamnosus GG (LGG-CM) regulate production of reactive oxygen species (ROS) and/or nitric oxide (NO) in macrophages. J774 macrophages in culture were loaded with either H₂DCFDA for monitoring ROS or with DAFFM-DA for NO detection. Free radical production was measured on a fluorescence microplate reader and changes were analysed by Cumulative sum (CuSum) calculations. Low concentration of LGG-CM (10% LGG-CM) or LPS did not cause any significant change in basal levels of ROS or NO production. In contrast, high concentration of LGG-CM (75% and 100%) significantly enhanced ROS generation but also significantly reduced NO level. These findings are novel and suggest for the first time that probiotics may release factors in culture which enhance ROS production and may additionally reduce deleterious effects associated with excessive nitrogen species by suppressing NO level. These events may account, in part, for the beneficial bactericidal and anti-inflammatory actions ascribed to probiotics and may be of clinical relevance.

Disruption of Transitional Stages in 24-h Blood Pressure Recording in Renal Transplant Recipients

Patients with kidney replacement exhibit disrupted circadian rhythms. Most studies measuring blood pressure use the dipper/non-dipper classification, which does not consider analysis of transitional stages between low and high blood pressure, confidence intervals nor shifts in the time of peak, while assuming subjective onsets of night and day phases. In order to better understand the nature of daily variation of blood pressure in these patients, we analyzed 24 h recordings from 41 renal transplant recipients using the non-symmetrical double-logistic fitting assessment which does not assume abruptness nor symmetry in ascending and descending stages of the blood pressure profile, and a cosine best-fitting regression method (Cosinor). Compared with matched controls, double-logistic fitting showed that the times for most transitional stages (ascending systolic and descending systolic, diastolic, and mean arterial pressure) had a wider distribution along the 24-h. The proportion of individuals without daily blood pressure rhythm in the transplanted group was larger only for systolic arterial pressure, and the amplitude showed no significant difference. Furthermore, the transplant recipient group had a less pronounced slope in descending systolic and ascending mean blood pressure. Cosinor analysis confirmed this phase-related changes, showing a wider distribution of times of peak (acrophases). We conclude that daily disruptions in renal transplant recipients can be explained not necessarily by an absence in diurnal variation, but also by changes in waveform-related parameters of the rhythm, and that alterations in the phase of the rhythm are the most consistent finding in these patients.

Different classifications of nocturnal blood pressure dipping affect the prevalence of dippers and nondippers and the relation with target-organ damage

OBJECTIVE

We assessed how different definitions of the awake and asleep periods and use of various blood pressure (BP) indices affect the extent of the nocturnal BP dip, the prevalence of dippers and nondippers, their respective reproducibilities and the relation of nondipping with target-organ damage.

METHODS

We performed 24-h ambulatory BP monitoring twice and determined the left ventricular mass index and urinary albumin excretion as indices of target-organ damage in 150 hypertensive patients (off-medication). Awake and asleep periods were assessed using fixed and diary time methods, covering all readings available (wide) or excluding morning and evening transition hours (narrow). Nondipping (BP dip < 10%) was established for systolic BP and diastolic BP, their combinations (and/or), and mean arterial pressure.

RESULTS

The different awake-asleep definitions caused significant variation in both the extent of the BP dip and the number of dippers and nondippers in comparison with the wide diary definition (i.e. use of actual awake and sleep periods). The prevalences of dippers and nondippers also varied significantly with the BP index. Reproducibility analyses of the BP dip and the dipping status yielded repeatability coefficients (expressed as percentages of nearly maximal variation) between 42.39 and 48.71%, and kappa values between 0.323 and 0.459, respectively. Some classifications, but not all, discriminated significantly between consistent dippers and nondippers in terms of left ventricular mass index or urinary albumin excretion.

CONCLUSIONS

Use of different definitions of awake-asleep and BP indices affects significantly the classification of nocturnal BP dipping and its relation with hypertensive target-organ damage.

Is parent-child interaction therapy effective in reducing stuttering?

PURPOSE

To investigate the efficacy of parent-child interaction therapy (PCIT) with young children who stutter.

METHOD

This is a longitudinal, multiple single-subject study. The participants were 6 children aged 3;3-4;10 [years;months] who had been stuttering for longer than 12 months. Therapy consisted of 6 sessions of clinic-based therapy and 6 weeks of home consolidation. Speech samples were videorecorded during free play with parents at home and analyzed to obtain stuttering data for each child before therapy, during therapy, and up to 12 months posttherapy.

RESULTS

Stuttering frequency data obtained during therapy and posttherapy were compared with the frequency and variability of stuttering in the baseline phase. Four of the 6 children significantly reduced stuttering with both parents by the end of the therapy phase.

CONCLUSIONS

PCIT can reduce stuttering in preschool children with 6 sessions of clinic-based therapy and 6 weeks of parent-led, home-based therapy. The study highlights the individual response to therapy. Suggestions for future research directions are made.

The International Database of Ambulatory Blood Pressure in relation to Cardiovascular Outcome (IDACO): protocol and research perspectives

OBJECTIVES

The International Database on Ambulatory Blood Pressure Monitoring (1993-1994) lacked a prospective dimension. We are constructing a new resource of longitudinal population studies to investigate with great precision to what extent the ambulatory blood pressure improves risk stratification.

METHODS

The acronym IDACO refers to the new International Database of Ambulatory blood pressure in relation to Cardiovascular Outcome. Eligible studies are population based, have fatal as well as nonfatal outcomes available for analysis, comply with ethical standards, and have been previously published in peer-reviewed journals. In a meta-analysis based on individual patient data, composite and cause-specific cardiovascular events will be related to various indexes derived by ambulatory blood pressure monitoring. The analyses will be stratified by cohort and adjusted for the conventional blood pressure and other cardiovascular risk factors.

RESULTS

To date, the international database includes 7609 patients from four cohorts recruited in Copenhagen, Denmark (n=2311), Noorderkempen, Belgium (n=2542), Ohasama, Japan (n=1535), and Uppsala, Sweden (n=1221). In these four cohorts, during a total of 69,295 person-years of follow-up (median 9.3 years), 1026 patients died and 929 participants experienced a fatal or nonfatal cardiovascular event. Follow-up in five other eligible cohorts, involving a total of 4027 participants, is still in progress. We expect that this follow-up will be completed by the end of 2007.

CONCLUSION

The international database of ambulatory blood pressure in relation to cardiovascular outcome will provide a shared resource to investigate risk stratification by ambulatory blood pressure monitoring to an extent not possible in any earlier individual study.

Non-dipolar content of the T-wave as a measure of repolarization inhomogeneity in ST-elevation myocardial infarction

The non-dipolar content of the T-wave, i.e. the component of the signal, which cannot be explained by a dipolar model, has been suggested as a measure of the local repolarization inhomogeneity. Our purpose was to study the non-dipolar content of the T-wave during the initial course of ST-elevation myocardial infarction (STEMI), when local repolarization inhomogeneity presumably is markedly increased. Twelve-lead ECG was semicontinuously collected in 211 patients with STEMI, treated with a thrombolytic agent. The T-wave was processed by principal component analysis. The absolute and relative T-wave residues were used as measures of the non-dipolar content. The median values for each hour and for the entire monitoring time were computed. Changes in the parameters were closer studied in two windows, 0-10 respectively, 11-24 h after start of ECG-monitoring. The median of the absolute T-wave residue during the entire monitoring period was 25 000 units in the STEMI-group and 13 500 units in the comparison group. The median for hour 1 was 36 500 units and 28 800 units for hour 2. The decrease was greater in patients with >or=50% resolution of the ST-elevation at 60 min. The moment of change, identified by cumulative sum-method, showed no correlation to the time for 50% ST-resolution. We conclude, that patients with thrombolysed STEMI have an increased non-dipolar content of the T-wave. Resolution of the ST-elevation is associated with a decrease. The increased non-dipolar content reflects a property of the repolarization phase, which is related to but separated from the ST-elevation.

Factors affecting the use of cumulative sums in the analysis of circadian blood pressure

The assessment of circadian blood pressure change by ambulatory blood pressure monitoring has potential as a predictor for cardiovascular events, but its evaluation is problematic due to the difficulty in defining day and night periods for individual subjects. The cumulative sums (cusums) method has the advantage of simplicity over mathematical modelling techniques and is reported to give more reproducible results than methods that use time-dependent sleep and wake periods. However, cusum parameters (cusum-derived circadian alteration magnitude (CDCAM) and cusum plot height (CPH)) are affected by the implementation of the method and by the quality of ambulatory blood pressure recordings. This study quantifies the effects of using interval blood pressure values, changing the time used for calculating the cusum plot slope (CPS) and using incomplete data recordings. Significant effects are reported in all cases. Using interval rather than recorded blood pressures causes a mean reduction in CPH and CDCAM of approximately 6%. Altering the CPS time by 1 h (from 6 h) results in a mean change in CDCAM of approximately 7%. In recordings with hourly readings, the coefficient of variation in CPH and CDCAM ranges from 4% (one missing reading) to 13% (five missing readings).

Application of the CuSum Technique to Evaluate Changes in Recruitment Strategies

BACKGROUND

While lagging subject enrollment in longitudinal clinical trials is a complex problem, the best recruitment strategy has not been established. Cumulative summation (CuSum) is a statistical process control procedure often applied in quality improvement efforts to detect trend shifts in highly variable serial data.

OBJECTIVES

To describe changes in efforts to increase referrals and enrollment in a longitudinal quality-of-life breast cancer study, determine effects of changes in referral strategies on enrollment using a novel application of CuSum, and discuss implications of CuSum as a tool for prospectively managing the subject recruitment process.

METHOD

Ten referrals and eight enrollments per month for a total of 31 months were estimated to meet study subject accrual requirements in the clinical trial. The estimates were used as standards in performing CuSum calculations. CuSum was applied to monthly referral and enrollment data and trend graphs were generated. Alterations in recruitment tactics and strategies were evaluated as to whether changes in trend occasioned such alterations. Unplanned changes in trend were noted.

RESULTS

While monthly data were highly variable, an average of 8.42 referrals and 5.92 enrollments were realized during Months 1-12. Based on these figures, projected accrual for 31 months would have enrolled only 184 subjects, 66 subjects short of target. CuSum illustrated this trend. Subsequent shifts in enrollment trends were shown with improvements in referral.

DISCUSSION

Indications for use of CuSum include (a) earlier detection of enrollment trend shifts, and (b) earlier discrimination between effective and ineffective recruitment. Thus, CuSum has implications for both evaluating the effects of planned and unplanned process changes and for managing the recruitment process.

Accumulation of Physical Activity Reduces Blood Pressure in Pre- and Hypertension

PURPOSE

The effectiveness of lifestyle physical activity to reduce BP in prehypertension/hypertension is unclear. The purpose of this study was: 1) to investigate the magnitude and duration of ambulatory BP (AmBP) reduction after the accumulation of one day of lifestyle physical activity (PAaccum) in normotension, prehypertension, and hypertension; and 2) to determine the relationship between energy expenditure (EE) and BP reduction.

METHODS

Subjects were eight normotensive (112.3/73.1 +/- 1.6/1.9 mm Hg), 10 prehypertensive (124.3/79.3 +/- 1.2/1.6 mm Hg), and 10 hypertensive (139.7/83.3 +/- 3.7/3.7 mm Hg) adults. EE was analyzed during the PA and corresponding control (C) treatment; AmBP was analyzed for 12 h after the PAaccum and corresponding C. EE of the PA (EEPA) was calculated as the total EE for the duration of the PA. Steps to analyze and compare the BP reduction after PAaccum were: 1) determination of the duration of the BP reduction (95% CI), 2) determination of the magnitude of the BP reduction (paired t-tests of C vs PA), 3) determination of the area of the BP reduction, and 4) comparison of the areas (independent t-test) between prehypertension and hypertension. Correlation between EE(PA-C) and BP reduction was examined

RESULTS

No BP differences were found for normotension or for DBP in any group. Significant difference in SBP after the PAaccum were found for prehypertensives (magnitude; area = 6.6 +/- 2.3 mm Hg; 21.7 +/- 15.2 mm Hg x h(-1)) for 6 h and for hypertensives (12.9 +/- 4.3 mm Hg; 123.4 + 42.8 mm Hg x h(-1)) for 8 h; area was significantly different between groups. No correlation was found between EE(PA-C) and BP reduction.

CONCLUSION

The PAaccum reduces SBP in hypertension and prehypertension but does not appear to be related to the EE(PA-C). PAaccum can be utilized as an approach to treat prehypertension and hypertension.

Disruption of Ultradian and Circadian Rhythms of Blood Pressure in Nondipper Hypertensive Patients

Ultradian rhythms in blood pressure (BP) are known to exist, but their modification in hypertension is largely unknown. The present study was undertaken to assess the integrity of ultradian and 24-hour BP rhythms in dipper (n=100) and nondipper (n=20) hypertensive patients compared with 44 dipper normotensive individuals. Fourier analysis was used to fit ultradian (12, 8, and 6 hour) and 24-hour rhythms in BP and heart rate (HR). Mesor, amplitude, and acrophase were calculated for individual and overall rhythm curves. All subjects showed significant ultradian or 24-hour BP and HR rhythms. Systolic and diastolic BP mesor was higher in hypertensive patients compared with normotensive patients. The percentage of variability in ambulatory BP that could be explained by fitting ultradian and 24-hour rhythms was reduced in nondippers compared with normotensives or dippers. Amplitude of ultradian and 24-hour rhythms in BP increased in dippers and decreased in nondippers. Ultradian and 24-hour rhythms in HR did not differ among the 3 groups examined. Results indicate that in nondippers, blunted ultradian and 24-hour rhythm amplitude in BP was accompanied by a loss of rhythm integrity.

Normative values for circadian and ultradian cardiovascular rhythms in childhood

To assess the prevalence and characteristics of physiological circadian (24-hour) and ultradian (12-, 8-, and 6-hour) rhythms of mean arterial blood pressure (BP) and heart rate (HR), we analyzed 24-hour ambulatory BP profiles from 938 healthy school children aged 5 to 18 years. Cosine harmonics were fitted by Fourier analysis, and an amplitude and acrophase (time of peak) were calculated for each rhythm. Ninety percent of children displayed circadian rhythmicity of BP, independent of age, whereas circadian HR rhythmicity decreased with puberty from 96% to 87% (P<0.0001). Puberty had marked effects on the prevalence of ultradian rhythmicity: 12- and 6-hour rhythms increased for BP (27% to 47%, P<0.0001; 18% to 25%, P=0.01) and HR (36% to 47%, 17% to 31%, both P=0.001), whereas 8-hour BP rhythms decreased (34% to 23%, P=0.002). Median amplitudes were 10.1, 5.9, 5.6, and 5.2 mm Hg for the 24-, 12-, 8-, and 6-hour BP rhythms, respectively, and 13.4, 7.7, 6.8, and 6.4 bpm for HR. The acrophase occurred at approximately 14:00 hours, 8:00 hours, 5:30 hours, and 2:00 hours (military time) for the four BP rhythms, and at 13:30 hours, 08:30 hours, 01:50 hours, and 02:00 hours for HR. For the combined curve, the peak-trough difference was 25.9 mm Hg and 35 bpm for BP and HR, respectively, with the peaks occurring at 13:50 hours and 13:10 hours. There was marked association between BP and HR rhythms, both for prevalence (P<0.0001 for coupling of BP and HR rhythms of the same period length) and timing, with a median time lag of BP after HR acrophase of only 21, 16, 13, and 5 minutes for the four rhythms, respectively.

Blood pressure lowering in essential hypertension with an oral renin inhibitor, aliskiren

Inhibition of the first and rate-limiting step of the renin-angiotensin system has long been an elusive therapeutic goal. Aliskiren, the first known representative of a new class of completely nonpeptide, orally active, renin inhibitors, has been shown to inhibit the production of angiotensin I and II in healthy volunteers and to reduce blood pressure (BP) in sodium-depleted marmosets. The aim of this randomized, double-blind, active comparator trial study was to assess the BP-lowering efficacy and safety of aliskiren. Two hundred twenty-six patients, 21 to 70 years of age, with mild to moderate hypertension, were randomly assigned to receive 37.5 mg, 75 mg, 150 mg, or 300 mg aliskiren or 100 mg losartan daily for 4 weeks. Dose-dependent reductions in daytime ambulatory systolic pressure (mean change, mm Hg [SD of change]; -0.4 [11.7], -5.3 [11.3], -8.0 [11.0], and -11.0 [11.0], P=0.0002) and in plasma renin activity (median change % [interquartile range]; -55 [-64, -11], -60 [-82, -46], -77 [-86, -72], and -83 [-92, -71], P=0.0008) were observed with 37.5, 75, 150, and 300 mg aliskiren. The change in daytime systolic pressure with 100 mg losartan (-10.9 [13.8]) was not significantly different from the changes seen with 75, 150, and 300 mg aliskiren. Aliskiren was well tolerated at all doses studied. This study demonstrates that aliskiren, through inhibition of renin, is an effective and safe orally active BP-lowering agent. Whether renin inhibition results in protection from heart attack, stroke, and nephropathy, similar to angiotensin-converting enzyme inhibition and angiotensin receptor blockade, needs to be researched.

A signal transduction pharmacodynamic model of the kinetics of the parasympathomimetic activity of low-dose scopolamine and atropine in rats

We used a novel pharmacokinetic-pharmacodynamic (PK-PD) approach that had been applied for signal transduction kinetics to investigate the kinetics of the parasympathomimetic effect of scopolamine and atropine in rats. The parasympathetic tone was assessed by continuous measurement of the power of the high frequency band (HF) of electrocardiogram (ECG) R-R intervals obtained by power spectral analysis (PSA) of heart rate variability (HRV). To overcome the inherent noise of the HRV-HF data and to quantitatively identify temporal changes in the autonomic tone, a new approach of stepwise regression of the cumulative HF data was applied. The elevation of the parasympathetic tone occurred after a significant lag time (>70 min) following scopolamine administrations [0.25 and 0.5 mg/kg intravenous (iv) bolus or infusion over 100 min], followed by a gradual return to the baseline levels. A similar lag time in parasympathetic stimulation was observed following iv bolus administration of atropine (0.1 mg/kg). The plasma drug concentration versus time data were linked to the response versus time data using a signal transduction pharmacodynamic model that was fitted simultaneously to all four experimental data sets. This PK-PD model resolved the significant discrepancy between the concentration versus time and the response versus time patterns and successfully described the kinetics of the parasympathetic stimulation obtained for different drugs and different rates of administration. This work paves the way for further PK-PD preclinical investigations in this field.

Blood pressure, cardiac structure and severity of obstructive sleep apnea in a sleep clinic population

OBJECTIVES

We investigated whether the severity of obstructive sleep apnea (OSA) predicts blood pressure or cardiac left ventricular thickness in a clinical population of OSA patients, if adjustments are made for age, gender, use of antihypertensive agents, smoking, body mass index, history of coronary artery disease, hypercholesterolemia and circulating C-peptide concentrations.

DESIGN

Relationships in this cross-sectional study were investigated with correlation analysis and multiple regression procedures.

PATIENTS AND METHODS

Apnea-hypopnea index (AHI, polysomnography) and office systolic and diastolic blood pressures (SBP and DBP) were measured in 81 subjects referred to a university hospital sleep laboratory. Ambulatory blood pressures were recorded during one 24 h cycle. Left ventricular (LV) muscle size was quantified as two-dimensionally directed M-mode-derived end-diastolic thickness of interventricular septum and posterior chamber wall.

RESULTS

After adjustment for separate or the entire set of covariates, AHI predicted office SBP and DBP as well as daytime ambulatory DBP and night-time ambulatory SBP and DBP, but not daytime ambulatory SBP. In contrast, associations between AHI and LV muscle thickness reflected complex inter-relationships with confounding variables. Smoking and age suppressed, whereas body mass index (BMI) and hypertension inflated the relationship between OSA severity and LV muscle thickness in this study.

CONCLUSIONS

AHI is an independent predictor of several measures of blood pressure. OSA severity and LV muscle thickness appear to be primarily linked via increased blood pressure.

Cumulative plot of heart rate variability spectrum assesses kinetics of action of cholinergic drugs in rats

A new approach to assess autonomic nervous system (ANS) activity and its response to drug action is presented. Our approach is based on the use of a cumulative plot of data obtained by power spectral analysis of heart rate variability, in defined frequency bands, during short time epochs (e.g., 2 min in rats). The substantial temporal variability in power evolving from the constant balancing nature of the ANS activity is minimized by this approach and produces a measurable index of ANS activity vs. time. The cumulative plot emphasizes the temporal response pattern of different components of the ANS and thereby facilitates the investigation of the kinetics of action of drugs affecting the ANS. We used this method to measure the activity of cholinergic drugs in freely moving Sabra rats. Bolus atropine doses between 0.5 and 2 mg/kg produced a similar magnitude of effect, reduction of the ascending slope by 0. 003 power units/h, whereas the duration of this effect was dose dependent. A lower atropine dose (0.1 mg/kg) or 0.5 mg/kg scopolamine elevated the slope (0.074 and 0.054 power units/h for 206 and 216 min, respectively). The method was used similarly to assess the interaction between cholinergic drugs. Pretreatment with pyridostigmine produced temporal blockage of the anticholinergic activity of atropine.

Comparison of atenolol, amlodipine, enalapril, hydrochlorothiazide, and losartan for antihypertensive treatment in patients with obstructive sleep apnea

We compared the effects of atenolol (50 mg), amlodipine (5 mg), enalapril (20 mg), hydrochlorothiazide (25 mg), and losartan (50 mg) given in once-daily oral doses on office and ambulatory blood pressures (BPs) in patients with hypertension and obstructive sleep apnea (OSA). Each of 40 randomized patients was treated in sequence with two of the five agents (balanced incomplete block design). Treatment periods lasted 6 wk and were separated by a 3-wk washout period. Changes in BP from baseline with the study substances were compared through analysis of variance. Office diastolic BP, our primary outcome variable, was most effectively lowered by atenolol, with all four post hoc differences between atenolol and the remaining substances being statistically significant. Reductions in office systolic and daytime ambulatory BP were not significantly different among the five compounds. However, atenolol reduced mean nighttime ambulatory diastolic and systolic BP more effectively than did amlodipine, enalapril, or losartan (but not hydrochlorothiazide). Severity of sleep-disordered breathing and well-being during the day were not significantly influenced by any of the study compounds. Our findings are in accordance with the hypothesis that an overactivity of the sympathetic nervous system is an important mechanism behind the development or maintenance of hypertension in patients with OSA.

Innovative methods for monitoring perinatal health outcomes in cities and in smaller geographic areas

OBJECTIVES

Monitoring health in small localities such as cities or local communities is important, because rates of adverse outcomes often vary widely by geographic area. This article explores the utility of CUSUM (cumulative summation), a method developed and refined in industry, for monitoring health outcomes in cities and smaller geographic areas.

METHODS

CUSUM monitoring methods were applied to rates of late or no prenatal care initiation and very low birthweight for the city of Baltimore as a whole and for a cluster of high-risk areas within the city. The performance of supplementary runs criteria was also assessed. The ability of both methods to flag significant increases or decreases in prenatal care initiation and very low birthweight rates was assessed.

RESULTS

CUSUM and runs criteria detected most significant rate changes. The 2 methods performed better in regard to outcomes with higher prevalence and in larger geographic areas.

CONCLUSIONS

CUSUM methods are convenient and reliable for use in the monitoring of moderately low prevalence outcomes in small geographic areas. Future research should examine their applicability to other health outcomes and further refine these methods, especially for rarer outcomes.

Significance of sympathetic nervous system in sodium-induced nocturnal hypertension

OBJECTIVE

The purpose of this study was to investigate the effects of salt loading on circadian patterns of blood pressure (BP) and sympathetic nervous activity.

SUBJECTS AND METHODS

Seventy-six patients with essential hypertension were hospitalized and placed on a low-salt diet (2 g/day) for 7 days followed by a high-salt diet (20-23 g/day) for another 7 days. On the last day of each salt diet, 24 h ambulatory BP, plasma noradrenaline concentrations, urinary noradrenaline excretion, plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were measured. Patients whose average mean BP was increased by more than 10% by salt loading were assigned to the salt-sensitive (SS) group (n = 44); the remaining patients, whose mean BP was increased by less than 10%, were assigned to the non-salt-sensitive (NSS) group (n = 32).

RESULTS

Salt loading converted the circadian pattern of BP from dippers, whose mean BP during the night-time was decreased by more than 10% from the daytime BP, to non-dippers in the SS group but not in the NSS group. A nocturnal decrease in plasma noradrenaline concentration was unaffected after salt loading in the NSS group but dampened in the SS group. The night-time/daytime ratio of urinary noradrenaline excretion, which was increased after salt loading in the SS group only, was greater in the SS group than in the NSS group under the high-salt diet. The salt-induced suppression rate of PRA and PAC was similar between the SS and NSS groups.

CONCLUSION

BP fails to fall during the night under the high-salt diet in patients with the SS type of essential hypertension. This may be related to the lack of nocturnal decrease in sympathetic nervous activity.

Diurnal blood pressure change varies with stroke subtype in the acute phase

BACKGROUND AND PURPOSE

It is unclear whether acute stroke is associated with a loss of the normal diurnal blood pressure (BP) change and whether stroke type influences this. Some of this confusion results from the use of fixed time definitions of day and night, which can be overcome by the use of cumulative sums analysis (cusums).

METHODS

Ninety-eight stroke patients had 24-hour BP monitoring (Spacelabs 90207) performed within 48 hours of ictus. Three subgroups were identified: cortical infarct, n=50; subcortical infarct, n=29; and primary intracerebral hemorrhage [PICH], n= 19. An age-matched control group of 74 subjects was also studied. Diurnal change was assessed by both day-night differences (absolute and percentage) and cusums (cusums plot height [CPH] and circadian alteration magnitude [CDCAM]); ANCOVA was used to compare groups.

RESULTS

Compared with control subjects, cortical infarct and PICH subgroups had significantly reduced mean diurnal systolic changes using day-night differences (absolute, -12 and -17 mm Hg; percentage, -10 and -12, respectively; P < 0.0001) and cusums (CDCAM, -6.96 and -8.6 mm Hg; CPH, -32.05 and -46.04 mm Hg, respectively; P < 0.005), only the subcortical infarct subgroup demonstrated reduced percentage differences (-4.4%, P < 0.02). Mean diastolic differences were significantly reduced in all stroke subgroups(CPH, -24.84, -17.31, and -36.92 mm Hg; absolute, -8.26, -4.04, and -11.44 mm Hg; percentage, -10.65, -5.81, and -15.23%, for cortical infarct, subcortical infarct, and PICH subgroups, respectively; P < 0.05), except for CDCAM, which was not reduced in subcortical infarcts (-4.78 and -7.70 mm Hg for cortical infarct and PICH subgroups, respectively; P < 0.001).

CONCLUSIONS

Diurnal BP change was reduced in the 3 stroke subgroups studied, especially in patients with cortical infarcts and PICH. This may reflect damage to the central modulation of autonomic BP control. The implications in terms of prognosis and therapy in the acute period require further study.

Relationships between changes in left ventricular mass and in clinic and ambulatory blood pressure in response to antihypertensive therapy

OBJECTIVE

To analyse the relationships between changes in left ventricular mass in response to 6-month antihypertensive therapy and changes in conventional and automated measurements of clinic blood pressure, average 24 h ambulatory blood pressure and daytime and night-time blood pressures.

DESIGN

After a placebo run-in period, patients with essential hypertension (World Health Organization stages I-II) were treated for 6 months with one or a combination of two first-line antihypertensive drugs.

METHODS

Investigations included echocardiography, conventional and automated clinic blood pressure measurements and ambulatory blood pressure monitoring. Daytime and night-time blood pressures were assessed according to two clock-time-dependent and two clock-time-independent methods, with a wide and a narrow approach for each technique.

RESULTS

Fifty-four patients completed the 6-month treatment period. Left ventricular mass, adjusted for sex and body size, was correlated significantly to systolic and diastolic clinic blood pressures, both before (r = 0.57 and r = 0.48, P < 0.001) and during antihypertensive therapy (r = 0.43, P < 0.001 and r = 0.27, P < 0.05). Changes in left ventricular mass were significantly related to changes in blood pressure. The correlation coefficients amounted to 0.39 (P < 0.01) and 0.40 (P < 0.01) for the conventional and automated measurements of clinic systolic blood pressures, respectively, and to 0.45 (P < 0.001) for the average 24 h systolic blood pressure; these r values were 0.27 (NS), 0.20 (NS) and 0.43 (P < 0.01), respectively, for the diastolic blood pressure. The average 24 h blood pressure added 7.4% (P < 0.05) and 6.2% (P = 0.06) to the variance of the changes in mass explained in terms of the conventional and the automated measurements of clinic systolic blood pressures, respectively, and 11.2% (P < 0.05) and 14.5% (P < 0.01) for the diastolic blood pressures. The changes in daytime and night-time blood pressures predicted the changes in left ventricular mass significantly (P < 0.01) and to a similar extent, irrespective of the analytical method.

CONCLUSIONS

The treatment-induced changes in left ventricular mass were significantly related to the changes in clinic, 24 h, daytime and night-time blood pressures; the changes in 24 h ambulatory blood pressure add to the variance of the changes in left ventricular mass explained in terms of clinic blood pressure data.

Nocturnal fall in blood pressure in the elderly is related to presence of hypertension and not age

AIMS

To determine whether the reduced nocturnal fall in blood pressure (BP) reported in elderly hypertensives is due to ageing or to the presence of hypertension.

METHODS

Twenty-four hour ambulatory BP recordings of 68 normotensive elderly were compared with those of 55 elderly treated hypertensives, aged 63-88 years. Mean night-time BPs were calculated from the average of readings during sleep and mean daytime BPs from the remaining recordings. The maximum day-night BP differences were calculated. Plasma renin, aldosterone and noradrenaline were measured.

RESULTS

Normotensive subjects were aged 72.0 +/- 4.7 years and treated hypertensives 73.7 +/- 4.9 years (p = 0.049). Normotensives had lower systolic BP (SBP) than hypertensives (125 +/- 12 mmHg versus 135 +/- 14 mmHg, p < 0.01). The fall in SPB at night was greater in normotensives than in hypertensives (18 +/- 9 versus 14 +/- 9 mmHg, p < 0.02). Non-dipping occurred in 24% of all subjects, with 59% of these being hypertensives. The nocturnal fall in SBP was not related to age (beta = -0.04, p < 0.62) but was inversely related to a history of hypertension (chi (2) = 5.82, p = 0.02). Serum noradrenaline was significantly related to nocturnal SBP fall (beta = 0.28, p = 0.01).

CONCLUSIONS

Elderly normotensives have a greater decline in nocturnal SBP than treated elderly hypertensives. The failure of SBP to fall at night appears to be more a feature of hypertension than of ageing. Early morning noradrenaline estimations are higher in patients with a greater nocturnal blood pressure fall.

Individual assessment of antihypertensive response by self-starting cumulative sums

A self-interpreted control chart, on an individualized basis, assesses the effect of a switch from beta-blockers to an angiotensin-converting enzyme (ACE)-inhibitor in a patient with occasional blood pressure (BP) excess. In dense and long data series, the BP and heart rate (HR) of this patient respond to the change in treatment by the test criterion of a self-starting Cumulative Sum (cusum), which reaches values outside a decision interval with a lowering of BP and an increase in HR and vice versa, at least for BP, after treatment cessation. Thereafter, minimal sampling requirements are sought in the same data by applying the same control chart approach to decimated data. Skeleton sampling schemes in a system of chronobiologic self-analysis and interpretation of manually recorded data obtained at strategically placed times (established on the basis of data decimations) could complement control charts that are used on a home computer or preferably would be built into the output of ambulatory monitors used at the outset as a minimum and routinely as an optimum.

Prediction of cardiac structure and function by repeated clinic and ambulatory blood pressure

We performed imaging echocardiography, Doppler velocimetry, and repeated clinic and ambulatory blood pressure measurements in 74 hypertensive individuals to clarify why reports differ on the strength of the relationships of left ventricular characteristics with clinic blood pressure, on the superiority of ambulatory over clinic pressure, and on the importance of day-time and nighttime pressures. Clinic pressure was measured five times with an automated device and five times with the conventional technique on 2 different days. The partial correlation coefficients of left ventricular mass and wall thickness with the first automated systolic and diastolic clinic pressures amounted to .38 to .45 (P < .001), improved with increasing numbers of measurements, and reached .56 to .58 for the average of 10 automated pressure determinations. Similar trends were observed for conventional clinic pressures. Average 24-hour pressures were significantly related to mass and wall thickness (partial r = .50 to .61, P < .001) and explained 3% to 6% (systolic) and 5% to 12% (diastolic) of the variance of cardiac structure in addition to the first automated or conventional clinic pressure (P < .05). However, when 10 clinic measurements were averaged, only diastolic 24-hour pressure added information over and above clinic pressure (P < .05); the additional explained variance was larger with regard to the conventional (+4% for mass and +7% for wall thickness) rather than the automated (+3% for wall thickness only) pressures. Mass and wall thickness were more closely related to day-time than nighttime pressures and were not independently related to day-night differences in pressure, except when men and women were considered separately; the results were similar when four different definitions of day and night were applied. Finally, the weak association of left ventricular diastolic function with blood pressure did not improve on repeated clinic or ambulatory blood pressure measurements. In conclusion, increasing numbers of measurements strengthen the relationships of clinic pressure with left ventricular mass and wall thickness and, conversely, diminish the additional predictive power of 24-hour blood pressure. The importance of nighttime pressure and of the nighttime pressure fall does not seem to depend on the definition of day and night but differs in men and women.

Predictive value of ambulatory blood pressure shortly after withdrawal of antihypertensive drugs in primary care patients

OBJECTIVE

To determine whether ambulatory blood pressure eight weeks after withdrawal of antihypertensive medication is a more sensitive measure than seated blood pressure to predict blood pressure in the long term.

DESIGN

Patients with previously untreated diastolic hypertension were treated with antihypertensive drugs for one year; these were withdrawn in patients with well controlled blood pressure, who were then followed for one year.

SETTING

Primary care.

SUBJECTS

29 patients fulfilling the criteria for withdrawal of antihypertensive drugs.

MAIN OUTCOME MEASURES

Sensitivity, specificity, and positive and negative predictive value of seated and ambulatory blood pressure eight weeks after withdrawal of antihypertensive drugs.

RESULTS

Eight weeks after withdrawal of medication, mean diastolic blood pressure returned to the pretreatment level on ambulatory measurements but not on seated measurements. One year after withdrawal of medication, mean diastolic blood pressure had returned to the pretreatment level both for seated and ambulatory blood pressure. For ambulatory blood pressure, the sensitivity and the positive predictive value eight weeks after withdrawal of medication were superior to those for seated blood pressure; specificity and negative predictive value were comparable for both types of measurement. Receiver operating characteristic curves showed that the results were not dependent on the cut off values that were used.

CONCLUSION

Ambulatory blood pressure eight weeks after withdrawal of antihypertensive drugs predicts long term blood pressure better than measurements made when the patient is seated.

Ambulatory blood pressure monitoring. Application to clinical medicine and antihypertension medication trials

The wide use of ABPM has resulted in greater appreciation of the circadian time structure of BP variability and its clinical relevance. It is now recognized that the day-night change in BP results from an interplay of circadian rhythms in neurohumoral mechanisms coupled with temporal patterns in physical activity and mental load. The composite effect and balance of these endogenous and exogenous cyclic phenomena give rise to elevated BP during diurnal activity and reduced BP during nighttime repose in both normotension and uncomplicated essential hypertension. The balance is frequently disturbed in complicated and secondary forms of hypertension causing gross alteration of the 24-hour BP profile. ABPM also reveals the efficiency of antihypertensive treatment throughout the 24 hours and as a function of drug administration time. The pharmacokinetics and/or pharmacodynamics of antihypertensive medications have been demonstrated to vary with ingestion time. Such time-dependencies arise from circadian rhythms in BP and underlying mechanisms. The effect of antihypertensive medications is not simply superimposed upon endogenous bioperiodicities. Rhythms in neurohumoral mechanisms of BP control may modulate treatment effect. Certain aspects of the shape of the 24-hour BP profile, such as the magnitude of the morning surge and nocturnal decrease, have been implicated as determinants of morbid and mortal cardiovascular events. One large clinical multicenter investigation, known as the CONVINCE (Controlled Onset Verapamil Investigation of Clinical Endpoints) trial, is aimed at assessing the impact (cardiovascular morbidity and mortality) of verapamil chronotherapy over standard diuretic or beta anatagonist treatment in hypertensive patients with at least one risk factor of coronary heart disease. ABPM will help ascertain to what extent depression of the morning surge in BP relates to reduction in cardiac morbidity and mortality in this as well as other such trials. In any event, the importance of ABPM and the indices derived from its application are just beginning to be appreciated and explored.

Relationships of cardiac function and structure to blood pressure rhythms

It is well known that hemodynamic load is one of the most important determinants of cardiac structure and function. Circadian variations in blood pressure (BP) values are usually accompanied by consensual changes in peripheral resistance and/or cardiac output. In recent years, in hypertensive patients with left ventricular hypertrophy (LVH), a reduction in the circadian variations of BP and, in particular, a lack of nocturnal decline were observed; patients with only a small reduction in BP or none at all during the night were considered "non-dippers." In patients in whom a regression of LVH was obtained after prolonged antihypertensive therapy, restoration of the circadian rhythm of BP was also observed. However, the division of patients into "dippers" and "non-dippers" is arbitrary and poorly standardized and repeatable, and in the recent SAMPLE study, most hypertensive patients with LVH were dippers. Therefore, we should be particularly cautious about the conclusions drawn using this index. On the other hand, in patients with LVH, reduced activity of the low pressure cardiopulmonary baroreceptors and impaired day-to-night modulation of autonomic nervous system activity were observed. Therefore, cardiac structural alterations may possibly impair BP modulation; on the other hand, the opposite could also be true: a primarily altered BP modulation, through a persistently elevated afterload, could increase cardiac mass. Therefore, the interrelationships between cardiac structure and BP modulation are complex, and as a result, new and more specific methods of evaluation circadian changes in BP are needed to better clarify their reciprocal influences.

Polymorphism of angiotensin I converting enzyme gene in the older Chinese: linked to ambulatory blood pressure levels and circadian blood pressure rhythm

This study was undertaken to evaluate the association of polymorphism of angiotensin I converting enzyme (ACE) gene with causal and ambulatory blood pressure in the Chinese population. Genomic DNA was amplified by polymerase chain reaction (PCR) using primers flanking the polymorphic region in intron 16 of the ACE gene. Alleles were detected on agarose gels stained with ethidium bromide. Causal blood pressure was measured in the 133 normotensive and 122 essential hypertensive subjects; of the essential hypertensive subjects, 65 patients underwent non-invasive ambulatory blood pressure. There was no significant difference of ACE genotype and allele frequencies between the hypertensive and normotensive subjects. Non-significant differences were demonstrated in gender, age, causal blood pressure according to the ACE gene genotypes in the 65 patients who underwent non-invasive ambulatory blood pressure; however, effects of the ACE gene genotypes were observed on the derivatives of ambulatory blood pressure, including sleeping blood pressure levels and circadian blood pressure rhythm (p < 0.05). We suggest that insertion/deletion polymorphism of the ACE gene should be associated with blood pressure and ambulatory blood pressure might be superior to causal blood pressure at the molecular level.

Comparison of diurnal systolic blood pressure change as defined by wrist actigraphy, fixed time periods and cusum

AIMS

To assess whether differences exist in nocturnal blood pressure (BP) levels and the diurnal BP change when using fixed time and wrist actigraphy methods to define the night-time period.

METHODS

Untreated hypertensive (n = 48) and normotensive (n = 33) subjects (mean age 67 years: range 29-90) underwent simultaneous 24-h ambulatory BP monitoring and wrist actigraph monitoring. The diurnal BP change and nocturnal BP levels were assessed using two fixed night-time definitions-a reference period of 22.00-06.59 and also 00.00-05.59, as well as unedited and edited actigraph values and cumulative sums (cusums) analysis.

RESULTS

The reference definition of night-time 22.00-06.59 resulted in the highest values for night-time BP compared to other definitions (p < 0.05), although actigraph defined night-time BP values were not significantly different from the more restrictive definition of night-time (00.00-05.59). Restrictive night-time, edited and unedited actigraph and cusums values for the day-night difference were all significantly greater than the value calculated using the reference night-time period. Dipping status changed significantly depending on which definition of night-time was used.

CONCLUSIONS

Significant differences exist in nocturnal BP levels and circadian change between the various methods for defining night-time. The routine use of wrist actigraphy does not however appear to alter the value of night-time BP levels when compared to a more restrictive fixed-time definition of night-time.

Heritability of conventional and ambulatory blood pressures. A study in twins

Conventional and 24-hour ambulatory blood pressures were measured in 26 pairs of monozygotic twins and 27 pairs of dizygotic twins, all male, ages 18 to 38 years, to determine the heritability of blood pressure measured under various conditions. Conventional pressure was the average of three well-standardized measurements in the supine position, and ambulatory pressure was recorded during the subjects' normal activities by use of the SpaceLabs 90202 device. Heritability was assessed by classic methods and by model fitting and path analysis. In the latter approach, the percent genetic variance was 70% for mean 24-hour systolic pressure and 73% for diastolic pressure, which was similar to the results for the conventional pressures (64% and 73%, respectively). During the night, these estimates were 72% and 51% for systolic and diastolic pressures, respectively, and also the average pressures of the total awake daytime period were under partial genetic control (63% and 55%, respectively). The remaining variances could be attributed primarily to unique environmental influences. However, shared and nonshared environmental factors were predominant for the pressures during a fixed 6-hour afternoon period. We conclude that the heritability of blood pressure is relatively high in young adult healthy men, for standardized conventional pressure and the average 24-hour pressure. Genetic variance is somewhat higher for the asleep pressure than for the awake systolic pressure.

A consensus view on the technique of ambulatory blood pressure monitoring. The Fourth International Consensus Conference on 24-Hour Ambulatory Blood Pressure Monitoring

This review, based on the Fourth International Consensus Conference on Ambulatory Blood Pressure Monitoring (Leuven, Belgium, 1994), deals with the technical aspects of ambulatory blood pressure monitoring. Ambulatory blood pressure monitoring by noninvasive intermittent techniques is widely used despite artifacts due to cuff size, movement, body position, short-term blood pressure variability, and interference with sleep. The performance of the currently available monitors under truly ambulatory conditions and during exercise remains a matter of debate, as are the procedures required to validate portable monitors under these circumstances. There is general agreement that whenever a monitor is to be used in special populations, such as older subjects or pregnant women, or in special conditions, such as exercise, a specific demonstration of its accuracy in these defined subgroups or conditions is warranted. Whether the auscultatory or oscillometric method is preferred remains controversial because each technique has specific advantages and disadvantages and because both can provide accurate results. Most experts in the field strongly believe that manufacturers should disclose the algorithms of their devices and that they should specify all changes made to the hardware and software of a previously validated monitor. Finally, the development of the volume-clamp method, which makes continuous noninvasive registration of blood pressure at the finger possible in both stationary and ambulatory conditions, opens new perspectives in research, in particular in relation to short-term blood pressure variability.

Description of a new quotient that may differentiate blood pressure profiles in essential versus Cushing's syndrome-related hypertension

Since the presence or absence of a nocturnal decrease in blood pressure values (BP) may suggest an increased risk of visceral complications or the existence of secondary hypertension, several methods have been described for evaluating the BP profile. Nevertheless, a universally accepted system to evaluate this item has not yet been established. Our aim in this study was to test different dispersion quotients (DQ) which estimate the differences between the mean of each hour, and the mean of all the readings in the 24 h period. These quotients may be employed regarding systolic (SBP) or diastolic (DBP) blood pressure, and may be referred to the whole period of 24 h, or to the subperiods morning (m), afternoon (a) or night (n). We have studied two non selected groups of essential (n = 20) or secondary (Cushing's syndrome, n = 17) hypertensives. We observed a marked decrease in these quotients, particularly DQ-SBP and nDQ-SBP, in secondary hypertensives (respectively 10.2 +/- 2.9 vs 15.6 +/- 4.2 and 11.8 +/- 5.0 vs 20.5 +/- 6.3, p < 0.0001), thus indicating, a blunted nocturnal fall of BP in these patients. Also the DQ and particularly DQ-SBP, nDQ-SBP and nDQ-DBP, showed a high positive and negative predictive value, sensitivity and specificity for pertaining to the Cushing's syndrome group (respectively: 0.75, 0.88, 0.88, 0.75; 0.86, 0.82, 0.77 0.90; and 0.78, 0.84, 0.82, 0.80).

Effect of 24-h blood pressure levels and circadian blood pressure rhythm on left ventricular structure and function in isolated systolic hypertension

Forty-one participants (mean age 69 +/- 5.6 years) were examined by fully automatic blood pressure monitor and Doppler echocardiography to gain information on the ambulatory blood pressure and the left ventricular structure and function in isolated systolic hypertension. Cumulative sum (cusum)-derived statistics was used to quantify circadian blood pressure rhythm and 24-h blood pressure levels were defined as mean blood pressure values during 24 h, waking (06:00-22:00 h) and sleeping (22:00-06:00 h) periods, respectively. Most of the derivatives of ambulatory blood pressure, including cusum-derived statistics and 24-h blood pressure levels, were significantly related with the left ventricular structural (left ventricular posterior wall and interventricular septum thickness) and functional (acceleration time in the left ventricular outflow tract and early diastolic deceleration time) indexes. Among the left ventricular structural and functional indexes, interventricular septum thickness at end diastole had the strongest correlation with sleeping diastolic mean blood pressure (r = 0.41, P < 0.01), left ventricular posterior wall at end diastole, the best with 24-h systolic mean blood pressure (r = 0.41, P < 0.01), acceleration time the strongest with systolic cusum-derived circadian alteration magnitude (r = 0.49, P < 0.01) and early diastolic deceleration time the greatest with diastolic cusum-derived trough blood pressure (r = 0.45, P < 0.01). We conclude that left ventricular structural changes rely on 24-h systolic and diastolic blood pressure levels, whereas left ventricular functional variations may be more dependent upon circadian blood pressure rhythm in elderly patients with isolated systolic hypertension.

Antihypertensive therapy and circadian blood pressure profiles: a retrospective analysis utilising cumulative sums

The results of previous studies on the effects of antihypertensive agents on circadian blood pressure patterns are inconclusive, possibly due to the lack of a simple, objective, universally accepted method of quantifying circadian blood pressure profiles. In order to investigate for differences in the effects of antihypertensive drugs on circadian changes we utilised a recently described modified cumulative sums technique to quantify circadian alteration magnitude (CAM). CAM is simply calculated as the difference between crest and trough blood pressures, the mean blood pressures of the 6-h periods of highest and lowest sustained pressures respectively. The records from all 24-h ambulatory blood pressure monitoring performed over a 7 year period on subjects either on no medication (1208), or on treatment with a single first-line antihypertensive agent (578), were examined retrospectively. A sample (n = 40) stratified for trough diastolic blood pressure, age and sex was randomly selected from each of the following 5 groups: subjects on no medication, and subjects being treated with bendrofluazide, atenolol, class 2 calcium-channel blockers or captopril alone. Untreated subjects, those on bendrofluazide and those on a class 2 calcium channel blocker had similar circadian patterns. Subjects on atenolol therapy (25.9 +/- 1.7/18.3 +/- 1.3, systolic CAM +/- SE/diastolic CAM +/- SE) had attenuated circadian changes (p < 0.05) when compared to the untreated group (29.8 +/- 1.8/23.6 +/- 1.1), while those on captopril (34.9 +/- 2.4/25.7 +/- 1.8) exhibited markedly increased systolic and diastolic circadian blood pressure swings, which differed from those of the atenolol treated group (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)