Summer-winter variation in 24 h ambulatory blood pressure

OBJECTIVE: To examine possible seasonal differences in circadian blood pressure patterns and the specific contribution of indoor temperature. METHOD: Twenty-four-hour ambulatory systolic blood pressure (SBP) and diastolic blood pressure (DBP) were monitored once in summer and once in winter in 101 healthy subjects aged 28-63 years. Subjects were interviewed concerning health-related habits, and measurements of environmental and occupational conditions were obtained. RESULTS: After controlling for possible confounders, mean SBP during work was significantly higher in winter than in summer by 3.4 mmHg. Both in winter and in summer, the highest values were recorded during work. The daily SBP circadian amplitude was higher in winter, reflected by higher mean SBP during the day and lower mean SBP at night. All of the daytime DBP measurements were higher in winter than in summer, but at night there were no seasonal differences. The blood pressure showed an independent association with season and with environmental temperature (SBP) beta = 3.98 mmHg and -1.14 mmHg/ degrees C, respectively; DBP beta =4.39 mmHg and -0.58 mmHg/ degrees C, respectively).CONCLUSION: In healthy men, the daily amplitude of ambulatory blood pressure varies physiologically by season with the highest values being obtained during work time in the winter months. If these results can be extrapolated to hypertensives then it might be necessary to tailor drug therapy to these variations. The daily average or clinical measurements may lead to an underestimation of the extent of the seasonal variation in blood pressure. The season of the year must be controlled for in clinical and epidemiological studies comparing blood pressure levels and amplitudes between groups or between baseline and follow-up study.     

Classification of blood pressure levels by ambulatory blood pressure in hypertension

Whereas clinic blood pressure (CBP) above normality is divided into stages, no corresponding classifications are available for 24-hour ambulatory blood pressure (ABP). We conducted a study (1) to define stages of hypertension by ABP corresponding to CBP stages and (2) to evaluate if these stages have prognostic impact similar to CBP stages. Seven hundred thirty-six hypertensive patients were included. Mean systolic blood pressure was 149+/-15.2/87+/-8.6 mm Hg for CBP and 135+/-13/79+/-9.7 mm Hg for ABP. The mean bias between both methods was -13.3 mm Hg (95% CI, -14.3 to -12.2; 1.96xSD limits of agreement, 15.7 to -42.3) and -7.3 mm Hg (95% CI, -7.9 to -6.6; 1.96xSD limits of agreement, 9.8 to -24.3) for systolic and diastolic blood pressure (P>0.0001 for both), respectively. Classification of hypertension by ABP revealed lower cutoff values for the different stages of hypertension compared with the corresponding cutoff values for CBP (CBP versus ABP: 140/90 versus 132/81 mm Hg; 160/100 versus 140/88 mm Hg; 180/110 versus 148/94 mm Hg, P<0.001). Overall, 82 (11.1%) patients had nonfatal clinical cardiovascular events and 9 (1.2%) patients died of a cardiovascular cause during follow-up. The distribution of cardiovascular events was significantly associated with increasing ABP value (P<0.006). Staging of hypertension by ABP may facilitate the use of this method in daily clinical practice, as ABP can now be used not only to confirm the diagnosis of hypertension but also to assess the severity and prognosis of hypertensive disease.     

Genetic variation in the ASIC3 gene influences blood pressure levels in Taiwanese

BACKGROUND: The acid-sensing ion channel 3 (ASIC3) is a ligand-gated cation channel activated by extracellular protons, and is associated with an exercise-induced pressor reflex and possibly autonomic imbalance. METHODS: To test the statistical association between genetic polymorphisms of the ASIC3 gene and blood pressure (BP) variations in Taiwanese, 551 unrelated individuals (286 men and 265 women) were recruited from a routine health examination. The participants had no prior history of cardiovascular disease or medication use for hypertension. RESULTS: Six ASIC3 gene polymorphisms were genotyped; three were polymorphic, and only the rs2288646 polymorphism was associated with variations in BP among participants. Significantly higher systolic, diastolic, and mean BP were observed in participants carrying the rs2288646-A allele (P=0.034, 0.023, and 0.010, respectively). Significantly higher frequencies of the rs2288646-A-containing genotype were observed in normotensive, prehypertensive, and hypertensive subgroups (P for trend=0.026); and in those with higher systolic and diastolic BPs (P for trend=0.005 and P for trend=0.002, respectively). The association between the rs2288646-A allele and BP persisted even after adjustment for age, sex, BMI, and other metabolic factors. When a second independent group of 403 individuals was combined with the first group of 551 (n=954), a significantly higher frequency of the rs2288646-A-containing genotype was observed in participants with hypertension (9.7 vs. 4.0%, P=0.003). CONCLUSION: Our data showed an independent association between an ASIC3 genetic polymorphism and BP variations in Taiwanese. These results suggest that the ASIC3 may be involved in BP regulation.     

Assessment of blood pressure control in hypertensive stroke survivors: an ambulatory blood pressure monitoring study

BACKGROUND: We compared the sensitivity of office blood pressure and ambulatory blood pressure monitoring recordings in evaluating the effectiveness of antihypertensive treatment and identified factors related to inadequate blood pressure control among hypertensive stroke survivors. METHODS: Office blood pressure and ambulatory blood pressure monitoring measurements were performed at 120+/-30 days after ictus in 187 first-ever consecutive hypertensive stroke survivors who were receiving blood pressure-lowering medications according to international guidelines. Handicap was assessed by the modified Rankin Scale. Blood pressure was regarded as controlled if office and daytime ambulatory systolic and diastolic blood pressure values were <140/90 and <135/85 mmHg, respectively. Patients were subclassified according to the degree of their nocturnal systolic blood pressure fall [(mean daytime values-mean night-time values)100/mean daytime values] as dippers (>or=10%), nondippers (>or=0% and <10%) and reverse dippers (<0%). RESULTS: Effective blood pressure control was documented in significantly (P<0.001) fewer patients using ambulatory blood pressure monitoring (32.1%) than those using office recordings (43.3%), whereas in 16% of the study population a masked lack of per-treatment blood pressure control (elevated ambulatory blood pressure in the presence of normal office blood pressure levels) was identified. The distribution of dipping patterns differed significantly (P=0.01) between controlled hypertensive individuals (normal office and ambulatory measurements) and patients with isolated ambulatory hypertension (dippers: 31.3 vs. 10.0%; nondippers:56.9 vs. 53.3%; reverse dippers: 11.8 vs. 36.7%). Logistic regression analysis revealed diabetes mellitus and functional independency (modified Rankin Scale score<2) as independent predictors of inadequate blood pressure control. CONCLUSION: Ambulatory blood pressure monitoring detects a substantial number of treated hypertensive stroke survivors with a masked lack of per-treatment blood pressure control, who present a higher prevalence of abnormal circadian blood pressure patterns (reverse dipping). Diabetes mellitus and poststroke functional independency are the main factors contributing to inadequate blood pressure control.     

Genetic variation in the natriuretic peptide system and heart failure

Heart failure (HF) is a modern epidemic and is one of the few cardiovascular diseases which is increasing in prevalence. The growing importance of the Natriuretic Peptide (NP) system in HF is well recognized. Laboratory tests for B-type Natriuretic Peptide (BNP) have proven value as diagnostic and prognostic tools in HF and are now part of routine clinical care. Furthermore, recombinant atrial natriuretic peptide (ANP) (carperitide) and BNP (nesiritide) and are approved HF therapies in Japan and the US, respectively and additional natriuretic peptides (e.g., CNP, urodilatin, and designer NPs) are under investigation for use in HF. Common genetic sequence variants are increasingly being recognized as determinants of disease risk or drug response and may help explain a portion of the inter-individual variation in the human NP system. This review describes current knowledge of NP system genetic variation as it pertains to HF as well as ongoing studies and where the field is expected to progress in the near future. To briefly summarize, NP system genetic variants have been associated with alterations in gene expression, NP levels, and cardiovascular disease. The next step forward will include specific investigations into how this genetic variation can advance ‘Personalized Medicine’, such as whether they impact the utility of diagnostic BNP testing or effectiveness of therapeutic NP infusion. This is already in progress, with pharmacogenetic studies of nesiritide currently underway. We expect that within 5 years there should be a reasonable idea of whether NP system genetic variation will have important clinical implications.     

Reproducibility of blood pressure variation in older ambulatory and bedridden subjects

OBJECTIVES: We investigated the influence of ambulation on the reproducibility of circadian blood pressure variation in older nursing home residents. DESIGN: Ambulatory blood pressure monitoring was performed twice in 37 older nursing home residents. SETTING: Nursing home in Japan. PARTICIPANTS: Subjects included 18 ambulatory nursing home residents who had no limitation on physical activity and 19 bedridden residents who did not participate in physical activity. MEASUREMENTS: Twenty-four-hour, daytime, and nighttime blood pressure levels and their variability. RESULTS: The 24-hour and daytime variability of systolic blood pressure (SBP) was significantly greater in ambulatory than in bedridden subjects, whereas nighttime variability was similar. Significant correlations in SBP averaged for the whole day, daytime, and nighttime were observed between the two examinations in ambulatory (r =.80-.83) and bedridden (r =.83-.91) subjects, but the variabilities of SBP for the whole day and during the daytime of the first measurement were correlated with those of the second measurement in bedridden (r =.67 and r =.47, respectively) but not in ambulatory (r =.39 and r =.28, respectively) subjects. Significant correlations were found between the nocturnal SBP changes at two occasions in both ambulatory (r =.50) and bedridden (r =.51) subjects, but the dipper versus nondipper profiles, defined as reduction in SBP of greater than 10% versus not, showed low reproducibility in ambulatory subjects; five ambulatory (28%) and one bedridden (5%) subjects showed divergent profiles between the two examinations. CONCLUSIONS: The reproducibility of blood pressure variation in nursing home residents is influenced by ambulation.     

Left atrial size in 164 hypertensive patients: an echocardiographic and ambulatory blood pressure study

BACKGROUND: Left atrial enlargement (LAE) is associated with an increased risk of death and cardiovascular (CV) hospitalization. Whether or not LAE reflects early structural change from hypertension is unclear. HYPOTHESIS: The aim of this study was to evaluate the relationship between LA size, 24-h blood pressure measurements, age, body mass index (BMI), and left ventricular mass index (LVMI) in hypertensive patients. METHODS: We studied 164 outpatients (age range 30-76 years, 73 men and 91 women) with mild to moderate hypertension. Physical examination, electrocardiogram, noninvasive blood pressure monitoring (ABPM), Doppler echocardiogram were performed. Left ventricular mass index and LA dimensions were calculated. The sample was divided by age (< 60 and > or = 60 years). RESULTS: Left ventricular hypertrophy (LVH) was present in 45% of patients aged < 60 years and in 70% of patients aged > or = 60 years (p = 0.002). Left atrial enlargement (> 4 cm) was present in 35% of elderly and in 24% of young patients (p = 0.31), and in 36% of patients with and 21% of patients without LVH (p = 0.0057). There was no significant difference in the younger patients with and without LVH. The incidence of obesity was low (31%) in the whole sample. The percentage of overweight in the elderly patients with LVH and higher LA size was equally low. Multivariate analysis showed age (p = 0.044) and LVMI (p = 0.002) as the only significant predictors of LA enlargement. CONCLUSION: Since LAE is associated with a high risk of death and CV hospitalization, we emphasize the importance of development and use of drugs that inhibit LVH.     

Clinical implications of white coat hypertension: an ambulatory blood pressure monitoring study

Within routine clinical practice, white coat hypertension (where blood pressure is persistently higher in the presence of the doctor or nurse but normal outside the medical setting) makes the diagnosis and management of hypertension difficult. There are conflicting data regarding the prevalence and significance of white coat hypertension. This study has used ambulatory blood pressure monitoring to detect the presence of white coat hypertension in 186 patients referred to an out-patient hypertension unit. The presence of white coat hypertension was defined as an average office blood pressure (measured on three occasions over a 2-month period) of >140/90 mm Hg and an ambulatory awake blood pressure < or = 136/86 mm Hg. The prevalence of white coat hypertension in those patients with borderline hypertension (diastolic blood pressure 90-99 mm Hg) and those with mild-to-moderate hypertension (diastolic blood pressure > or = 100 mm Hg) was determined. Echocardiography was used to assess left ventricular mass index in patients with and without white coat hypertension. The prevalence of white coat hypertension in the total group was 23%. However, the prevalence was higher (33%) in those patients with borderline hypertension compared to 9% of those patients with mild-to-moderate hypertension. There was a statistically significant increase in left ventricular mass index in patients with no evidence of white coat hypertension (125 gm/m2) compared to those with white coat hypertension (102 gm/m2). We conclude that, if office blood pressure is used to identify patients with hypertension who may require treatment, some patients will be incorrectly diagnosed and may be treated inappropriately. We recommend that ambulatory blood pressure monitoring is used in the routine assessment of all newly diagnosed hypertensive patients. Furthermore, we recommend echocardiography in patients with borderline hypertension as some will already have an increased left ventricular mass index.     

老年高血压病人动态血压波动特征

目的：通过对调查资料的分析,了解和掌握老年高血压患者动态血压（ABP）波动特点。方法：分析707例虱的ABP测量资料,比较高血压病人和血压正常值的ABP以及ABP与诊室血压（CBP）之间的异同。结果：老年高血压患者的ABP主要表现为收缩压（SBP）和脉压（PP）升高,高血压患者和血压正常者的24小时ABP波动曲线类似,均呈双峰双谷状。结论：大动脉顺应性下降是SBP和PP升高的原因,老年人24小时ABP的波动特性可能是其自主神经功能失调的反映。     

Cigarette smoking and ambulatory blood pressure: a case-control study in normotensives

The aim of our study was the evaluation of the effects of cigarette smoking on ambulatory blood pressure (ABP) in normotensive subjects participating to a cardiovascular prevention program. All subjects were followed up for an average time of 97+/-42 months to assess the event of hypertension development. Prevalence of hypertension development was higher in smokers even if regression logistic analysis was not able to predict hypertension development.     

Reference values for the ambulatory blood pressure and the blood pressure measured at home: a population study.

In order to determine reference values for the ambulatory blood pressure, a population sample of 328 subjects, aged 20-81 years, who reported themselves to be in good health, was investigated. The ambulatory blood pressure was recorded over 24 h, taking measurements at 20 min intervals from 8 am to 10 pm, and at 45 min intervals from 10 pm to 8 am. Blood pressure was also measured by trained observers on each of two separate home visits (5 readings per visit). The ambulatory blood pressure in the 328 subjects averaged 118/71 mmHg over 24 h, 124/76 mmHg during the day (10 am-8 pm), and 108/62 mmHg at night (0 am-6 am). Blood pressure measured by an observer at the occasion of the second home visit was 4/5 mmHg lower (P less than 0.001) than the daytime ambulatory blood pressure. The 95th centiles for the daytime ambulatory pressures were 144/95 mmHg in 85 men below age 50; 154/90 mmHg in 74 men aged greater than or equal to 50 years; 132/85 mmHg in 96 women below age 50; and 151/91 mmHg in 73 women aged greater than or equal to 50 years. The 95th centiles for the nighttime pressures in these four sex-age groups were 124/79, 140/83, 121/70, and 132/72 mmHg, respectively.     

Effects of isoflavonoids on blood pressure in subjects with high-normal ambulatory blood pressure levels: A randomized controlled trial

Vegetarian diets lower blood pressure (BP), but attempts to identify dietary components responsible have been unsuccessful. Isoflavonoids are commonly consumed as part of vegetarian diets. The objective of this study was to assess the effect of isoflavonoid supplementation on BP. Fifty-nine subjects with high-normal range systolic BP completed a randomized, double blind, placebo-controlled trial of two-way parallel design and 8 weeks duration. One tablet containing 55 mg of isoflavonoids, including 30 mg of genistein, 16 mg of biochanin A (a genistein precursor), 1 mg of daidzein, and 8 mg of formononetin (a daidzein precursor), or one placebo tablet, was taken daily with the evening meal. Significant increases in urinary excretion of genistein (5.22 mg/day, 95% CI: 3.72, 6.72) and daidzein (2.53 mg/day, 95% CI: 1.66, 3.40) were observed in the group taking the isoflavonoid supplement. There were no significant changes in isoflavonoid excretion in the placebo group. Clinic BP was measured at two visits, and ambulatory BP monitoring was performed over one 24-h period, at baseline and postintervention. There was no significant difference between groups, after adjustment for baseline values, in postintervention clinic supine BP (systolic 1.2 mm Hg, 95% CI: −2.3, 4.7; diastolic 0.6 mm Hg, 95% CI: −1.9, 2.5), clinic erect BP (systolic 1.7 mm Hg, 95% CI: −4.0, 8.4; diastolic 0.4 mm Hg, 95% CI: −2.4, 3.2), or 24-h ambulatory BP (systolic −1.4 mm Hg, 95% CI: −4.4, 1.6; diastolic −0.8 mm Hg, 95% CI: −2.3, 0.7). Adjustment for age, gender, and weight change did not alter the result. Therefore, these results do not support the hypothesis that isoflavonoids, and genistein in particular, are major contributors to the BP lowering effect of vegetarian diets.     

Common genetic variation in the type A endothelin-1 receptor is associated with ambulatory blood pressure: a family study

The endothelins are among the most potent vasoconstrictors known. Pharmacological inhibition of endothelin receptors lowers blood pressure (BP). It is unknown whether naturally occurring genetic variation in the endothelin receptors influences BP. We have evaluated the type A endothelin receptor (EDNRA) as a candidate gene for hypertension in a large family study. A total of 1425 members of 248 families selected via a proband with hypertension were studied. Ambulatory BP monitoring was conducted using the A&D TM2421 device. Four haplotype-tagging single nucleotide polymorphisms (SNPs) spanning the EDNRA gene were typed. There was evidence of association between genotype at the rs5335 (C+70G) SNP and night systolic blood pressure (+1.24% (s.e. 0.64) per G allele; P=0.05); night diastolic blood pressure (+1.64% (s.e. 0.71) per G allele; P=0.021) and night mean BP (+1.51% (s.e. 0.64) per G allele; P=0.017). Borderline significant trends in the same direction were seen for daytime BPs. Proportions of hypertensives in each of the three genotype groups were C/C 34.7%, C/G 37.9%, G/G 42.4% yielding an odds ratio for hypertension per G allele of 1.19 (95% confidence interval 1.00-1.41; P=0.05). In conclusion, the rs5335 (C+70G) polymorphism of the EDNRA gene has small effects on the risk of hypertension. Natural variation in other genes in the endothelin-signalling pathway should be explored to identify additional influences on BP regulation.