Spectral analysis of 24 h blood pressure monitoring in the assessment of trough: peak ratio. A randomized, placebo-controlled, cross-over comparison of ramipril and enalapril

BACKGROUND: The ratio between the magnitude of blood pressure reduction during the steady-state dosage interval (trough) and the maximum blood pressure reduction (peak) is an integrated in-vivo index both of the pharmacokinetic properties and of pharmacodynamic activity of an antihypertensive drug. Angiotensin converting enzyme inhibitors are often characterized by a low (often lower than 50%) trough: peak ratio but no direct drug comparisons are available. OBJECTIVE: To compare the absolute blood pressure reduction and the trough: peak ratio of daily doses of two angiotensin converting enzyme inhibitors, 5 mg ramipril and 10 mg enalapril. METHOD: After a 1-month wash-out and a 2-week placebo run-in, 25 mild hypertensives aged 47 +/- 4 years (17 men and eight women) were randomly assigned to treatments separated by a 2-week interval. Ambulatory blood pressure monitoring was performed and trough: peak ratio was calculated by the fast Fourier transform analysis of placebo-effect-subtracted data. RESULTS: After 1 month of ramipril treatment, 24 h blood pressure decreased from 139 +/- 10 to 129 +/- 11 mmHg for systolic (P < 0.05) and from 89 +/- 8 to 81 +/- 5 mmHg for diastolic blood pressure (P < 0.01). Also enalapril treatment caused a significant 24 h reduction in blood pressure both for systolic (to 132 +/- 7 mmHg, P < 0.05) and for diastolic blood pressure (to 84 +/- 5 mmHg, P < 0.05). Placebo caused a 24 h reduction in blood pressure (to 136 +/- 8 mmHg for systolic and 87 +/- 5 mmHg for diastolic blood pressure, NS, versus wash-out period). The two drugs were equally effective in reducing ambulatory blood pressure, but ramipril produced a trough: peak ratio significantly higher than that with enalapril both for systolic (48 +/- 11%, range 34-74%, versus 38 +/- 11%, range 21-67%, P < 0.005)and for diastolic blood pressure (47 +/- 11%, range 30-79 %, versus 37 +/- 12%, range 21-68%, P < 0.05). CONCLUSION: The low trough : peak ratios could have been due to the daily pattern of blood pressure of mild hypertensives, many of whom are normotensives at night-time, so that the main antihypertensive effect is exerted during daytime rather than during the night or early morning.     

Impaired reduction of nocturnal systolic blood pressure and severity of diabetic retinopathy

The aim of the present study was to evaluate the influence of elevated levels of nocturnal blood pressure (BP) on diabetic retinopathy (DR). A total of 88 diabetic hypertensive patients were divided according to the stage of DR. They underwent 24 h ambulatory BP monitoring and ophthalmological evaluation, and their average level of fasting blood glucose as well as their glycemic control index (percentage of fasting blood glucose higher than 11.2 mmol/L over the previous four years) were calculated. When diabetic patients with retinopathy (n=29) (group 1) were compared with patients without retinopathy (n=59) (group 2), a significant difference was observed in diabetes duration (124 months [range six to 460 months] versus 43 months [range six to 365 months], respectively; P<0.05). In addition, group 1 showed higher levels of nocturnal systolic BP (NSBP) (141 +/- 22 mmHg versus 132+/-18 mmHg; P<0.05). However, no significant differences were found between the two groups (group 1 and group 2) when diurnal pressoric levels were compared (diurnal systolic BP, 153+/-19 mmHg versus 146+/-19 mmHg, P not significant; and diurnal diastolic BP, 91+/-9 mmHg versus 91+/-13 mmHg, P not significant). DR correlated with diabetes duration (r=0.26; P<0.05) and with glycemic control index (r=0.24; P<0.01). Multivariate regression analysis showed NSBP to be an independent predictor of DR (r(2)=0.12; P<0.01). Moreover, patients with severe stages of DR (preproliferative, proliferative or macular edema) showed a lower decrease of NSBP than the other patients (3.9+/-6.0 mmHg versus 9.2+/-6.0 mmHg; P<0.05). The present study suggests that the absence of 24 h normal pressoric rhythm can interfere with the prevalence and severity of DR.     

Sleep disturbance during ambulatory blood pressure monitoring of hypertensive patients

BACKGROUND: Hypertensive patients who fail to exhibit a normal fall in blood pressure at night may have a greater risk of target-organ damage. Sleep, with associated cessation of physical activity, is the principal determinant of nocturnal blood pressure 'dip'. OBJECTIVE: To ascertain whether hypertensive patients, who experience the discomfort of higher cuff-inflation pressures during ambulatory blood pressure monitoring, experience more interference with sleep, manifested by greater nocturnal physical activity. DESIGN: A retrospective case- control study. METHODS: Subjects were selected from a database of 475 patients who had undergone simultaneous 24 h ambulatory blood pressure monitoring and monitoring of physical activity with a wrist-mounted piezoelectric accelerometer. Sixty-one hypertensives (average daytime systolic blood pressure >/= 150 mmHg) were age matched to 61 subjects with average daytime systolic blood pressures 相似文献   

Variable day/night bias in 24-h non-invasive finger pressure against intrabrachial artery pressure is removed by waveform filtering and level correction

BACKGROUND Twenty-four-hour finger arterial pressure (FAP) recordings show a negative bias against intrabrachial artery pressure (BAP) and the bias is greater during the night, thereby overestimating the nocturnal blood pressure dip. We have available a methodology with which to reconstruct BAP from FAP by waveform filtering (transfer function) and generalized level (bias) correction that reduces the bias for short-term blood pressure records.OBJECTIVE To investigate if this methodology also decreases the extra bias during the night, thereby yielding a better estimate of the nocturnal dip.METHODS Twenty-four-hour FAP and BAP blood pressure recordings were simultaneously obtained in eight healthy normotensive volunteers and 14 patients with hypertension (ages 19-60 years), during standardized scheduled activities. The data were analysed off-line, applying the brachial reconstruction technique (reBAP) consisting of a waveform filter and level correction. Simultaneous beats yielded systolic, diastolic and mean pressures that were averaged per 30 min, per day, per night, per activity, over the 24-h period, and for volunteers and patients separately.RESULTS Over the full 24 h, FAP systolic, diastolic and mean values for the total group differed from BAP by +1 +/- 10, -8 +/- 7 and -10 +/- 8 mmHg (mean +/- SD), respectively. Similarly, reBAPs differed by +1 +/- 11, -2 +/- 7 and -2 +/- 7 mmHg. BAPs dipped by 20 +/- 8, 13 +/- 6 and 15 +/- 6 mmHg, respectively, during the night. These dips were overestimated by +8, +4 and +4 mmHg by FAP, but not by reBAP: -1, +1 and +1 mmHg. The volunteer and the patient groups showed slight differences in results, but these were not statistically significant.CONCLUSIONS The generalized reconstruction technique to obtain near-brachial pressure from non-invasive FAP almost completely removed bias over the full 24-h day-night period and improved tracking of diurnal changes for all three blood pressure values.     

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.     

Crossover study of amlodipine versus nifedipine CR with home blood pressure monitoring via cellular phone: internet-mediated open-label crossover trial of calcium channel blockers for hypertension (i-TECHO trial)

OBJECTIVE: We developed a new data collection system named i-converter that could transmit data to a website via cellular phone. Using the system, we compared the effects of two calcium channel blockers on the home blood pressure. METHODS: Amlodipine and nifedipine CR were administered to 41 patients with essential hypertension for more than 6 weeks each in a randomized open-label crossover study. The dose of each drug was increased until the home blood pressure reached the target level of under 135/85 mmHg. RESULTS: The morning home systolic and diastolic blood pressures were significantly lower during nifedipine CR treatment: 133 +/- 10/81 +/- 8 mmHg with amlodipine versus 131 +/- 8/80 +/- 8 mmHg with nifedipine CR, P < 0.05. The morning pulse rate was significantly higher during nifedipine CR treatment (69 +/- 9 beats/min with amlodipine versus 70 +/- 9 beats/min with nifedipine CR, P < 0.05). The evening home blood pressure and pulse rate, however, showed no significant differences between the two drugs (128 +/- 11/74 +/- 7 mmHg and 74 +/- 10 beats/min with amlodipine versus 128 +/- 10/75 +/- 7 mmHg and 74 +/- 9 beats/min with nifedipine CR, all not significant). CONCLUSIONS: Nifedipine CR had a stronger antihypertensive effect than amlodipine during the critical morning period, but the morning pulse rate was higher. Our new data transmission system was effective for collecting precise data on the blood pressure and pulse rate via the internet.     

Salt-loading elevates blood pressure and aggravates insulin resistance in Wistar fatty rats: a possible role for enhanced Na+ -H+ exchanger activity

OBJECTIVE : Increased Na+-H+ exchanger activity (NHE) has been reported as an intermediate phenotype in hypertensive subjects, particularly those with insulin resistance. To investigate whether NHE abnormality plays a role in hypertension, Wistar fatty rat (WFR) with overt obesity, hyperglycemia and marked hyperinsulinemia was examined. METHODS : WFR and Wistar lean rats (WLR) as a control (n = 12, each) were fed either with normal (0.38%) or high sodium (4% NaCl) diet for 12 weeks and then sacrificed to examine platelets NHE activity. RESULTS : Mean arterial pressure (MAP) was higher in WFR than in WLR (113 +/- 4 versus 96 +/- 7 mmHg, P < 0.05) under a normal chow. Vmax values of NHE activity were significantly higher in WFR than in WLR. WFR fed with a high sodium diet showed higher MAP than those with a normal chow (128 +/- 3 versus 113 +/- 4 mmHg, P < 0.05). Though Km values were not different between WFR and WLR under a normal chow, both maximal transport rate (Vmax) and half maximal transport (Km) values were significantly higher in WFR with a high salt diet than those with a control diet. Vmax showed significant correlation with MAP, whereas Km values correlated with immunoreactive insulin (IRI) levels. Significant interaction between dietary sodium intake and the strain differences was observed both on blood pressure and on IRI levels by two-way analysis of variance (ANOVA). CONCLUSION : WFR presented salt-sensitive blood pressure elevation. NHE activity was enhanced in WFR in correlation with the blood pressure. These results suggest that augmented NHE activity contributes to the development of salt-sensitive blood pressure elevation in WFR.     

Gender differences in the timing of arterial wave reflection beyond differences in body height.

OBJECTIVES: The timing of arterial wave reflection affects the shape of the arterial waveform and thus is a major determinant of pulse pressure. This study assessed differences in wave reflection between genders beyond the effect of body height. METHODS: From 1123 elderly (aged 71 +/- 5 years) currently untreated hypertensives, we selected 104 pairs of men and women with identical body height (average 164 +/- 4 cm). All subjects underwent echocardiography, including measurement of aortic arch expansion, automated blood pressure measurements, measurement of ascending aortic blood flow and simultaneous carotid artery tonometry. RESULTS: Women had higher pulse (80 +/- 17 versus 74 +/- 17 mmHg, P < 0.05) and lower diastolic pressure (79 +/- 11 versus 82 +/- 10 mmHg, P < 0.05). Whilst heart rate was similar, women had a longer time to the systolic peak (210 +/- 28 versus 199 +/- 34 ms, P < 0.01) and a longer ejection time (304 +/- 21 versus 299 +/- 25 ms, P < 0.001). Wave reflection occurred earlier in women (time between maxima 116 +/- 55 versus 132 +/- 47 ms, P < 0.05) and augmentation index was higher (36 +/- 11 versus 28 +/- 12%, P < 0.001). Aortic diameter was smaller in women and the aortic arch was stiffer (median Ep 386 versus 302 kN/m2, P < 0.05). Hence, systemic arterial compliance was less in women (0.8 +/- 0.2 versus 1.0 +/- 0.3 ml/mmHg). CONCLUSIONS: We conclude that elderly hypertensive men and women have a different timing of both left ventricular ejection and arterial wave reflection when both genders are matched for body height. Women have smaller and stiffer blood vessels resulting in an earlier return of the reflected wave, which is likely due to an increased pulse wave velocity in women.     

Diurnal blood pressure curve in children and adolescents

OBJECTIVE: To investigate the diurnal blood pressure curve in healthy normotensive children. Thirty-one children were re-examined after a median interval of 123 days in order to study the reproducibility of the diurnal profile. SUBJECTS: Twenty-four-hour ambulatory blood pressure monitoring and conventional blood pressure readings were obtained in 228 normotensive children, whose ages ranged from 6 to 16 years and of whom 116 were boys and 112 girls. RESULTS: The conventional blood pressure averaged 99+/-11/57+/-9 mmHg in boys and 98+/-12/56+/-9 mmHg in girls (means+/-SD); the corresponding 24 h pressures were 111+/-7/66+/-5 mmHg and 109+/-7/65+/-5 mmHg, respectively. Of the children, 83% had a significant diurnal blood pressure rhythm for systolic pressure and 89% for diastolic pressure. The nocturnal blood pressure fall was normally distributed, averaging 12.0+/-6.3 mmHg systolic and 14.2+/-5.9 mmHg diastolic. There was no evidence for a bimodal distribution. The amplitude of the diurnal blood pressure curve, determined by the Fourier approach, was positively skewed with a mean of 12.5+/-4.2 mmHg for systolic and 14.0+/-4.1 mmHg for diastolic blood pressure. The daily blood pressure maximum occurred at 1344+/-4 h 46 min for systolic and 1321+/-4 h 22 min for diastolic blood pressure. For systolic blood pressure the cumulative sum (cusum)-derived circadian alteration magnitude was 1.7+/-6.2 mmHg higher in boys than in girls, whereas the cusum plot height was also 7.3+/-27.0 mmHg x h higher in male subjects. The repeatability coefficient (2SD of the difference between paired recordings, expressed as a percentage of nearly maximal variation) was 80% for the conventional systolic pressure and 40% for the conventional diastolic blood pressure. The repeatability coefficients for the ambulatory blood pressure levels varied from 32 to 45% and for the parameters describing the diurnal blood pressure profile from 42 to 78%. CONCLUSION: A significant diurnal blood pressure rhythm is observed in most normotensive children and adolescents. There is no evidence for a bimodal distribution of the nocturnal blood pressure fall. The reproducibility of the parameters of the diurnal blood pressure curve tended to be less than that of the ambulatory blood pressure level. Thus, one 24 h recording is probably insufficient to characterize a child's diurnal blood pressure profile fully.     

A double-blind evaluation of captopril in elderly hypertensives

To establish the role of angiotensin converting enzyme inhibitors in the management of hypertension in the elderly, 16 patients were treated with captopril in a randomized double-blind placebo-controlled cross-over study. Clinic blood pressure, ambulatory blood pressure, renal function and mental performance, with emphasis on mood and psychological well-being, were assessed. Twelve patients, aged 73 (+/- 4.4) years, completed the study. The doses of captopril used were 50 mg (11 patients) and 25 mg (one patient) twice daily for 4 weeks. Mean (+/- s.e.m.) clinic sitting blood pressure during captopril therapy was significantly lower than during administration of placebo (172 +/- 4.5/83 +/- 25 versus 188 +/- 4.4/89 +/- 3.4 mmHg; P less than 0.001/P less than 0.05). Mean ambulatory blood pressure was also significantly lower on captopril treatment than during administration of placebo (166 +/- 5.3/87 +/- 1.6 versus 179 +/- 5.1/94 +/- 2.4 mmHg; P less than 0.02/P less than 0.02) and this effect was sustained over the dosing interval. Renal blood flow and mental performance were unaltered by treatment. Gastrointestinal discomfort occurred in two patients, one of whom was withdrawn and cough developed in one patient. We conclude that captopril is effective as monotherapy in lowering blood pressure in the elderly.     

Tolerability and antihypertensive efficacy of Fosinopril on 24-hr ambulatory blood pressure in hypertensive elderly subjects

The tolerability and antihypertensive efficacy of Fosinopril were assessed in 34 elderly patients with mild to moderate hypertension. Twenty-four-hour ambulatory blood pressure (BP) was measured before and after 5 months of therapy. The patients' mean age was 67 years. At the end of the treatment the mean 24-hour systolic BP (SBP) fell from 153.4 +/- 14 to 137.7 +/- 13 mmHg and the mean 24-hour diastolic BP from 91 +/- 11 to 84.2 +/- 9 mmHg (p < 0.01). The mean decrease in SBP was 15.9 mmHg during the day and 10.3 during the night, and in diastolic BP (DBP) 8.3 mmHg during the day and 10.3 mmHg during the night (p < 0.05 between day and night). There was no significant percentage difference between the SBP and DBP decreases. The mean morning maximum of SBP decreased from 171 +/- 18 to 158 +/- 19 mmHg and there was a reduction in pressure increase between the night and day. The number of SBP peaks over 180 mmHg and 160 mmHg numerically decreased to 20.1% and 37.6% versus baseline, those of DBP over 105 mmHg and 95 mmHg to 41.6% and 58.3% versus baseline, respectively. There were no variations in the blood chemistry parameters and the drug had no adverse side effects. The authors conclude that Fosinopril is useful and well tolerated in the treatment of moderate hypertension in the elderly.     

Twenty-four hour ambulatory blood pressure monitoring pattern of resistant hypertension

OBJECTIVE: Ambulatory blood pressure monitoring (ABPM) is a tool to diagnose resistant hypertension (RH). The objective of this study is to describe the pattern of 24-h ABPM in patients using at least three anti hypertensive drugs without blood pressure (BP) control, classifying them as true RH or white-coat RH. METHODS: A cross-sectional study involving resistant hypertensives that were submitted to clinical, laboratory and 2D-echocardiographic evaluation. Ambulatory blood pressure monitoring was used to diagnose true or white-coat RH. The chi-squared test was used for comparisons among categorical variables and Kruskall-Wallis test for continuous ones. RESULTS: Of the 286 patients, 161 (56.3%) were classified as true RH and 125 (43.7%) as white-coat RH. Sex, age, office BP and the cardiovascular risk factors for both groups were similar. True resistant hypertensives had more target organ damage then white-coat resistant hypertensives; nephropathy (40.1 versus 23.9%, P=0.007) and left ventricular hypertrophy (83.3 versus 76.3%, P=0.05). In ABPM, the true RH group had a smaller nocturnal systolic and diastolic BP reduction (6.4+/-8.8 versus 9.8+/-7.5 mmHg, P=0.0004; 10.4+/-9.6 versus 13.6+/-9.2 mmHg, P=0.001) and 68.7% of them were non-dippers versus 49.6% in the white-coat RH group (P=0.001). True RH also had a larger 24 h pulse pressure (65.8+/-13.7 versus 51.5+/-10.0 mmHg, P < 0.0001). CONCLUSIONS: Ambulatory blood pressure monitoring is a fundamental tool to diagnose RH, and to check treatment efficacy. The presence of a greater pulse pressure and a lower nocturnal blood pressure reduction in true RH patients may be responsible for this increased cardiovascular risk profile.     

Superiority of home blood pressure measurements over office measurements for testing antihypertensive drugs

OBJECTIVE: To compare the effects on office blood pressure and home blood pressure of placebo and active drug administration. DESIGN: After a 2-week wash-out period, patients with mild-to-moderate hypertension entered a 2-week single-blind placebo period and then a 4-week double-blind period. Patients were randomly assigned to be administered either 2 mg trandolapril once daily or its placebo in a 2:1 proportion. Office blood pressure was measured by a physician at the end of each period, using a mercury sphygmomanometer (mean of three consecutive measurements). Home blood pressure was measured during the last week of each period according to standard procedure carefully taught to each patient by the physician. Compliance was checked by using electronic pill boxes. RESULTS: Data for 34 of the 44 patients who entered the study were eligible for analysis. Baseline systolic blood pressure/diastolic blood pressure were significantly (P = 0.0001/P = 0.0001) higher for office blood pressure (161/101 mmHg) than they were for home blood pressure (145/93 mmHg). There was no statistically significant difference between the placebo and active-treatment groups at baseline. During the single-blind period, blood pressures measured at the office and at home did not change significantly. Office blood pressure decreased by 2.7 +/- 10 mmHg for systolic blood pressure and by 0.5 +/- 4 mmHg for diastolic blood pressure whereas home blood pressure increased by 0.8 +/- 6 mmHg for systolic blood pressure and by 0.7 +/- 4 mmHg for diastolic blood pressure. During the double-blind period, office blood pressure fell significantly with trandolapril treatment (systolic by 10.2 +/- 12 mmHg, diastolic by 8.3 +/- 6 mmHg; P = 0.0005/0.0001, versus single-blind placebo period) but this decrease was not significantly different (P = 0.45/0.92) from the fall in members of the placebo group (systolic by 6.9 +/- 9 mmHg, diastolic by 8.0 +/-6 mmHg; P = 0.04/0.002, versus single-blind placebo period). Thus, no antihypertensive effect of trandolapril was demonstrated. The fall lin home blood pressure with trandolapril treatment was significant (systolic by 10.7 +/- 8 mmHg, diastolic by 5.8 +/- 5 mmHg; both P = 0.0001, versus single-blind placebo period) and was significantly greater (P = 0.0004/0.004) than the minimal change observed with placebo (systolic fell by 0.2 +/- 5mmHg, diastolic fell by 0.6 +/- 4 mmHg; P = 0.90/0.62, respectively, versus single-blind placebo period). The evening decrease in home blood pressure was similar to the morning decrease in home blood pressure in members of the trandolapril-treated group. The resulting morning:evening decrease in blood pressure ratio was 0.83 for diastolic blood pressure and 0.95 for systolic blood pressure. For the subgroup of responders, mean of individual ratios was 0.77 +/- 0.43 for diastolic blood pressure and 0.70 +/- 0.39 for systolic blood pressure. CONCLUSION: The placebo effect observed with office blood pressure measurements does not occur with home blood pressure measurements. Expected treatment effect can alter a physician's blood pressure readings. The precision of measurements is greater with home blood pressure (there is a lower SD). Use of home blood pressure measurements increases the power of comparative trials, allowing one either to study fewer subjects or to detect a smaller difference in blood pressure.     

Systematic error in the determination of nocturnal blood pressure dipping status by ambulatory blood pressure monitoring

BACKGROUND: Vertical displacement of the arm relative to the heart causes inverse changes in blood pressure of approximately 0.8 mmHg for every centimetre change in arm position. Therefore a potential confounding issue in assessing diurnal variation in blood pressure during ambulatory blood pressure monitoring (ABPM) is arm position during sleep. An increase in the number of patients with 'excessive' nocturnal dipping (> 20% decrease in night/day blood pressure) was observed following the creation of an instructional videotape in which patients were advised to muffle the noise of the monitor with a pillow at night. This raised the possibility that patients were placing their arm on top of the pillow reducing nocturnal blood pressure readings. DESIGN: Ambulatory blood pressure monitoring data from 184 patients prior to and from 193 patients following specific instructions not to put their arm on top of the pillow was examined. RESULTS: Following the instructions, the percentage of patients with 'excessive' nocturnal dipping in blood pressure decreased (excessive systolic dipping 17.4 versus 8.8%, P = 0.014; excessive diastolic dipping 37 versus 24.4%, P = 0.01). Consistent with an increase in the ratio of nocturnal/day pressures, there was an increase in the percentage of patients with inadequate nocturnal dipping (< 10% decrease in night/day blood pressure; systolic dipping 33.7 versus 45.6%, P = 0.02; diastolic dipping 13.0 versus 31.6%, P < 0.001) CONCLUSION: Instructing patients to avoid resting their arm on a pillow at night has a substantial effect on the classification of nocturnal dipping status. Patients need clear instructions not to place their arm on a pillow at night during blood pressure monitoring.     

High sodium diet and circulating digitalis-like compound in the rat

The effects of a high salt diet (8% NaCl) on blood pressure and intra-erythrocytic Na+ content were studied in Wistar rats. The ability of the plasma to inhibit the renal Na+,K+-ATPase activity and to cross-react with digoxin antibodies was also investigated. After 1 week, neither systolic blood pressure nor intra-erythrocytic Na+ content were modified, but plasma extracts slightly inhibited renal Na+,K+-ATPase (70.9 +/- 1.7 versus 76.3 +/- 2.1 mumol Pi/mg per h, P = 0.05). After 2 weeks, the plasma inhibitory activity, systolic blood pressure and intra-erythrocytic Na+ content were higher than corresponding values in control animals (65.5 +/- 1.6 versus 79.1 +/- 2.8 mol Pi/mg per h, P less than 0.001; 132 +/- 2 versus 114 +/- 4 mmHg, P less than 0.001, and 4.95 +/- 0.32 versus 3.81 +/- 0.36 mmol/l cells, P less than 0.05, respectively). After 3 months, the plasma digoxin-like immunoreactivity and its ability to inhibit the Na+ pump were elevated (68.7 +/- 7.9 versus 48.2 +/- 5.4 pg/ml, P less than 0.02; 57.8 +/- 1.8 versus 72.9 +/- 1.8 mumol Pi/mg per h, P less than 0.001, respectively) whereas intra-erythrocytic Na+ content had returned to control levels. The results demonstrated that this high salt intake led to simultaneous increases in systolic blood pressure and in the activity of a digitalis-like compound present in plasma. The inhibition of Na+,K+-ATPase was correlated with systolic blood pressure and digoxin-like immunoreactivity (r = 0.569, n = 76, P less than 0.001 and r = 0.414, n = 34, P less than 0.02, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Similarity of spontaneous and induced heart rate and blood pressure turbulence

BACKGROUND: Heart rate turbulence (HRT) is a transient tachycardia-bradycardia that follows premature ventricular complexes (PVCs). The physiology of turbulence is studied in the electrophysiology lab using induced premature ventricular stimuli but the reliability of this model for HRT is unknown. OBJECTIVES: To compare heart rate and blood pressure signatures of induced and spontaneous HRT. METHODS: Each patient received 10 ventricular extrastimuli at 1-min intervals. Electrocardiogram and continuous blood pressure results were digitized for 34 electrophysiology patients. RESULTS: Fifteen patients yielded at least one induced and one spontaneous analyzable PVC. Per subject, 3.6+/-2.2 spontaneous and 6.1+/-3.3 induced HRT sequences were detected. Spontaneous and inducible HRT were indistinguishable according to turbulence onset (median -1.7% versus -2.3%, P=0.09), turbulence slope (median 7.1 ms/beat versus 10.0 ms/beat, P=0.73), turbulence tachycardia (median 29 ms versus 22 ms, P=0.97) and turbulence bradycardia (45 ms versus 72 ms, P=0.60). Accompanying blood pressure signatures were indistinguishable according to initial hypotension (-0.5+/-5.9 mmHg versus 12.1+/-5.5 mmHg, P=0.19), hypertension time (7.7+/-3.6 s versus 7.8+/-1.9 s, P=0.93) and turbulence hypertension (13.5+/-5.7 mmHg versus 16.1+/-9.2 mmHg, P=0.19). Baroreflex sensitivities estimated by the spontaneous sequence method were similar for spontaneous and induced turbulence (median 7.5 ms/mmHg versus 7.2 ms/mmHg, P=0.89) and correlated with each other (r2=0.81). Heart rate and blood pressure turbulence induced in the electrophysiology laboratory were similar to those following spontaneous PVCs and induced turbulence was a valid model for study under controlled conditions.     

Relationship of baroreflex sensitivity and blood pressure in an older population

OBJECTIVES: Ageing and hypertension are associated with reduced baroreflex sensitivity (BRS) in young and middle-aged populations. The effects of blood pressure level on BRS in the older population are unclear. We examined the association between blood pressure and BRS in older persons with blood pressure below 180 mmHg. METHODS: BRS, high (alphaHF 0.15-0.4 Hz) and low (alphaLF 0.04-0.15 Hz) frequency alpha-index, was determined in 75 normotensive subjects (aged 75 +/- 4 years, 41% female, 131 +/- 10/74 +/- 7 mmHg) and 64 untreated hypertensive subjects (aged 76 +/- 5 years, 48% female, 165 +/- 7/ 88 +/- 7 mmHg) by spectral analysis of 20 min continuous blood pressure and heart rate recordings using finger plethysmography. Subjects were recruited from 10 general practices and were taking no cardiovascular medications. RESULTS: High but not low frequency alpha-index was significantly blunted in hypertensive subjects (alphaHF 5.1 +/- 3.1 versus 8.4 +/- 7.4 ms/mmHg, P< 0.001 and alphaLF 4.7 +/- 3.0 versus 5.8 +/- 3.9 ms/mmHg, P= 0.07). Multivariate analysis of the relationship between age and blood pressure demonstrated systolic and to a lesser extent diastolic blood pressure were significant predictors of variance in BRS for alphaHF [systolic blood pressure (SBP) P< 0.0001, diastolic blood pressure (DBP) P< 0.05, r2 = 0.1] and alphaLF (SBP P=0.01, DBP P<0.05, r2 = 0.04). Age was not a significant predictor for either measure, in the 20 year range studied. CONCLUSIONS: In an older population blood pressure is associated with reduced BRS, particularly for the high frequency component. Such a change may place older subjects with hypertension at increased risk of orthostatic hypotension, vasovagal syncope and sudden cardiac death.     

Comparison of the effects of amlodipine and losartan on 24-hour ambulatory blood pressure in hypertensive patients

Effects of amlodipine (AML), a long-acting calcium antagonist, and losartan (LOS), an angiotensin II receptor antagonist, on 24-hr blood pressure profile were compared in 15 patients with essential hypertension. After 4 weeks of placebo period, the patients were treated with AML or LOS in a random crossover design for 12-16 weeks each. Either drug was given once daily at 0800 and the doses were titrated so that the office blood pressure was reduced lower than 140/90mmHg. At the end of each period, 24-hr blood pressure was monitored. Average office blood pressure was lowered from 158 +/- 2/ 98 +/- 2 mmHg to 134 +/- 1/87 +/- 1 mmHg by AML and 134 +/- 2/88 +/- 1 mmHg by LOS. Average 24-hr blood pressure was also reduced from 144 +/- 3/ 92 +/- 2 mmHg to 131 +/- 2/84 +/- 2 mmHg by AML and 135 +/- 3/85 +/- 2 mmHg by LOS. The averaged 24-hr systolic blood pressure was significantly lower in AML than in LOS (p < 0.05). Then, the 24-hr blood pressure was analyzed for four segments; morning (0530-0900 h), daytime (0930-1800 h), evening (1830-2300 h) and night (2330-0500 h). Although the daytime blood pressure was comparable between AML and LOS, systolic blood pressure in the evening and morning hours were lower in AML than in LOS (133 +/- 2 vs. 138 +/- 3mmHg,p<0.01; 129 +/- 3 vs. 134 +/- 4,p<0.05). Troughtopeakratio of antihypertensive effect on systolic blood pressure was significantly greater in AML than in LOS (62 +/- 5% vs. 55 +/- 4%, p < 0.05). Either drug did not cause reflective increase in pulse rate over 24 hours. These results suggest that both AML and LOS are equally effective in lowering daytime blood pressure without eliciting reflex tachycardia, however, the antihypertensive effect of AML lasts longer than that of LOS. Such information seems important to achieve 24-hr blood pressure control using these drugs.     

Does potassium supplementation lower blood pressure? A meta-analysis of published trials.

Both epidemiologic and clinical studies have suggested that an increase in potassium intake may lower blood pressure. However, the results of prospective clinical trials looking at the effect of oral potassium supplements on blood pressure have yielded conflicting results. For this reason, we reviewed 19 clinical trials examining the same end-point and involving a total of 586 participants (412 of whom had essential hypertension). Overall, the results of the trials indicate that oral potassium supplements significantly lower systolic blood pressure [-5.9 mmHg, -6.6 to -5.2 mmHg (mean, 95% confidence interval)] and diastolic blood pressure (-3.4 mmHg, -4.0 to 2.8 mmHg). The magnitude of the blood pressure lowering effect is greater in patients with high blood pressure (-8.2 mmHg, -9.1 to -7.3 mmHg for systolic and -4.5 mmHg, -5.2 to -3.8 mmHg for diastolic blood pressure) and appears to be more pronounced the longer the duration of the supplementation (P less than 0.05 and P less than 0.01 for systolic and diastolic, respectively). Based on this analysis, an increase in potassium intake should be included in the recommendations for a non-pharmacological approach to the control of blood pressure in uncomplicated essential hypertension.     

Predictive value of clinic blood pressure variability for pressure changes during placebo in elderly hypertensives

OBJECTIVES: Syst-China is the ongoing placebo-controlled double-blind outcome trial in older (aged 60 years or more) Chinese patients with isolated systolic hypertension (systolic blood pressure 160-219 mmHg and diastolic blood pressure < 95 mmHg). This article is based on the data accumulated until 31 August 1992. Its purpose is to investigate the extent to which the variability in the clinic blood pressure readings at baseline could predict the blood pressure changes observed in the placebo arm of the trial. METHODS: From 2379 patients recruited into the trial, 728 [455 men and 273 women, aged 66.7+/-5.5 years (mean +/- SD)] were selected, because their blood pressure readings for the three run-in visits as well as 3, 6 and 12 months after random allocation were available. Overall and between-visit blood pressure variabilities at baseline were estimated from the two readings obtained with the subject seated during the first and second run-in visits. The baseline blood pressure used to calculate the blood pressure changes during follow-up was the average of the two readings during the third run-in visit. RESULTS: The blood pressure variability at baseline was larger for women than it was for men. For all of the subjects combined, the blood pressure had decreased by 4.1+/-14.4 mmHg (P < 0.001) systolic and 0.5+/-6.7 mmHg (P < 0.06) diastolic by the 3-month follow-up visit, by 8.5+/- 15.2 and 1.4+/-7.5 mmHg, respectively, after 6 months and by 10.3+/-15.7 and 1.9+/-7.9 mmHg, respectively, after 1 year (p < 0.001 for all). Stepwise multiple regression analysis showed that sex, age, alcohol intake and the blood pressure at baseline were significant determinants of the long-term (1 year) blood pressure changes. Aftger adjustment for the aforementioned covariates, the between-visit variability was a significant predictor of the changes in the diastolic blood pressure after 1 year of placebo treatment for the men (partial r+/-SEM -0.36+/-0.12, P < 0.01) and for all of the subjects (-0.19+/-0.09, P < 0.05). For men, the partial regression coefficient between the overall variability and the changes in the diastolic blood pressure also attained statistical significance (-0.39+/- 0.14, P < 0.01). CONCLUSION: For older Chinese patients with isolated systolic hypertension, in particular for men, a higher blood pressure variability at baseline was associated with a larger decrease in diastolic blood pressure during 1-year follow-up on placebo, explaining up to 2% of the variance of the observed changes. Similar associations were not observed for systolic blood pressure.