Ambulatory blood pressure monitoring

Evaluation of hypertension by ambulatory blood pressure monitoring in children with solitary kidney

In this study, we aimed to investigate the blood pressure (BP) profile in children with a unilateral functioning solitary kidney (UFSK). A group of 49 patients between the ages of 5 and 18 years, and 30 healthy controls between the ages of 6 and 16 years were investigated. Gender, weight, height and body mass index (BMI) of patients and controls were recorded. BP profile was determined by ambulatory BP monitoring (ABPM). We have observed a higher risk of hypertension compared with healthy children. Also, masked hypertension is more frequently in the patients group and white-coat hypertension was observed in the control group. The mean night-time systolic BP (SBP) load (p = 0.01) and 24-h diastolic BP (DBP) load (p = 0.008) of children with multicystic dysplastic kidney (MCDK) was significantly higher than the healthy group. The mean night-time SBP load (p = 0.001) of children with unilateral renal agenesis (URA) and 24-h DBP load (p = 0.003) of children with unilateral atrophic or hypoplastic kidney were significantly higher than healthy group. We showed that the children with a solitary kidney had increased risk of hypertension. ABPM reflects the BP profile more precisely than casual BP measurement and it can be used to evaluate white-coat and masked hypertension in children with a solitary kidney.

Antihypertensive therapy: nocturnal dippers and nondippers. Do we treat them differently?

Hypertension is a major independent risk factor for cardiovascular diseases. Management of hypertension is generally based on office blood pressure since it is easy to determine. Since casual blood pressure readings in the office are influenced by various factors, they do not represent basal blood pressure. Dipping of the blood pressure in the night is a normal physiological change that can be blunted by cardiovascular risk factors and the severity of hypertension. Nondipping pattern is associated with disease severity, left ventricular hypertrophy, increased proteinuria, secondary forms of hypertension, increased insulin resistance, and increased fibrinogen level. Long-term observational studies have documented increased cardiovascular events in patients with nondipping patterns. Nocturnal dipping can be improved by administering the antihypertensive medications in the night. Long-term clinical trials have shown that cardiovascular events can be reduced by achieving better dipping patterns by administering medications during the night. Identifying the dipping pattern is useful for decisions to investigate for secondary causes, initiating treatment, necessity of chronotherapy, withdrawal or reduction of unnecessary medications, and monitoring after treatment initiation. Use of this concept at the primary care level has been limited because 24-hour ambulatory blood pressure monitoring has been the only method for documenting dipping/nondipping status so far. This monitoring technique is expensive and inconvenient for routine usage. Simpler methods using home blood pressure monitoring systems are evolving to document basal blood pressure in the night, which would help in greater acceptance and use of the concept of dipper/nondipper in managing hypertension at the primary care level.

Ambulatory blood pressure monitoring and structural changes in carotid arteries in normotensive workers occupationally exposed to lead

Occupational exposure to lead may cause an increase in blood pressure. The aim of the study was to estimate the effect of occupational exposure to lead on selected parameters of ambulatory blood pressure monitoring (ABPM) and structural changes in carotid arteries. The study included 33 normotensive men occupationally exposed to lead and 39 unexposed men employed in administration of the foundry. All of the men underwent 24-hour ambulatory blood pressure monitoring and high-resolution B-mode ultrasonography to determine intima-media thickness (IMT). The group of men occupationally exposed to lead manifested significantly higher mean systolic blood pressure (MSBP), mean diastolic blood pressure (MDBP), mean blood pressure (MBP), pulse pressure (PP), variability of diastolic blood pressure (VDBP), and IMT than the unexposed group. The studied groups did not differ in mean values of variability of systolic blood pressure (VSBP). As compared to the unexposed group, in men exposed to lead, atherosclerotic plaques were significantly more common. In the group of persons exposed to lead the Pearson’s correlation coefficient analysis revealed significant linear positive correlations between MSBP and IMT, between lead level and the number of atherosclerotic plaques, and between lead level and PP. Multivariate stepwise regression analysis demonstrated that higher lead level in blood and higher triglyceride concentration in blood represent independent risk factors of an increased pulse pressure in the group of individuals occupationally exposed to lead. Occupational exposure to lead can be associated with increased blood pressure and accelerated progression of atherosclerosis.

Indication-specific 6-h systolic blood pressure thresholds can approximate 24-h determination of blood pressure control

Ambulatory blood pressure monitoring (ABPM) is an accurate method for evaluating hypertension, yet its use in clinical practice may be limited by availability, cost, and patient inconvenience. The objective of this study was to investigate the ability of a 6-hour ABPM window to predict blood pressure control, based on that of the full 24-hour ABPM session across several clinical indications in a cohort of 486 patients referred for ABPM. Sensitivities and specificities of the 6-hour systolic blood pressure mean to accurately classify patients as hypertensive were determined using a fixed reference point of 130 mmHg for the 24-hour mean. For four common indications in which ABPM was ordered, prediction tables were constructed varying the thresholds for the 6-hour mean to find the optimal value that best predicted the 24-hour hypertensive status as determined from the full 24-hour interval. Using a threshold of 137 mmHg for the indications of borderline hypertension, evaluation of current antihypertensive regimen and suspected white-coat hypertension, sensitivity and specificity ranged from 0.83–0.88 and 0.80–0.88, respectively, for the ability of 6-hour ABPM to correctly categorize hypertensive status. Using 133 mmHg as the threshold for treatment resistance resulted in a sensitivity and specificity of 0.93 and 0.83, respectively. We conclude that a shortened ABPM session of 6 hours can be used to accurately classify blood pressure as controlled or not, based on the results of a 24-hour session. The optimal 6-hour threshold for comparison depends upon indication for referral.

Blood pressure responses to lifestyle physical activity among young, hypertension-prone African-American women

BACKGROUND

Physical inactivity and obesity increase the risk for hypertension, and both are more prevalent in African-American than Caucasian women. Regular physical activity serves as an important intervention for reducing cardiovascular risk, yet the ideal physical activity profile to meet the needs of young, sedentary African-American women remains unclear. We performed a randomized, parallel, single-blind study to examine the effect of lifestyle physical activity (LPA) on blood pressure indices in sedentary African-American women aged 18 to 45 years with prehypertension or untreated stage 1 hypertension.

METHODS

The primary intervention was an 8-week individualized, home-based program in which women randomized to Exercise (n = 14) were instructed to engage in lifestyle-compatible physical activity (eg, walking, stair climbing) for 10 minutes, 3 times a day, 5 days a week, at a prescribed heart rate corresponding to an intensity of 50% to 60% heart rate reserve. Women in the No Exercise group (n = 10) continued with their usual daily activities. Mean changes in cuff, ambulatory, and pressure load indices were compared using paired t tests, and physical activity adherence was expressed as percentages.

RESULTS

Women in the Exercise group had a significant reduction in systolic blood pressure (-6.4 mm Hg, P = .036), a decrease in diastolic blood pressure status to the prehypertensive level (90.8 vs 87.4 mm Hg), and greater reductions in nighttime pressure load compared with the No Exercise group. Adherence to LPA was exceedingly high by all measures (65%-98%) and correlated with change in systolic blood pressure (r = -0.620, P = .024).

CONCLUSION

The accumulation of LPA reduced cuff, ambulatory, and pressure load. The accumulation of LPA appears well tolerated and feasible in this sample of young African-American women, demonstrated by the overall high adherence rates. Given the excess burden of pressure-related clinical sequelae among African Americans and the strong correlation between pressure load and target organ damage, LPA may represent a practical and effective strategy in this population.

Continuous blood pressure monitoring during exercise using pulse wave transit time measurement

This paper gives an overview of a research, which is focused on the development of the convenient device for continuous non-invasive monitoring of arterial blood pressure. The blood pressure estimation method is based on a presumption that there is a singular relationship between the pulse wave propagation time in arterial system and blood pressure. The parameter used in this study is pulse wave transit time (PWTT). The measurement of PWTT involves the registration of two time markers, one of which is based on ECG R peak detection and another on the detection of pulse wave in peripheral arteries. The reliability of beat to beat systolic blood pressure calculation during physical exercise was the main focus for the current paper. Sixty-one subjects (healthy and hypertensive) were studied with the bicycle exercise test. As a result of current study it is shown that with the correct personal calibration it is possible to estimate the beat to beat systolic arterial blood pressure during the exercise with comparable accuracy to conventional noninvasive methods.

The interplay between haemodynamic load, brain natriuretic peptide and left atrial size in the early stages of essential hypertension

OBJECTIVE

Left atrial (LA) enlargement is an index of adverse cardiovascular events. We sought to investigate any possible correlation between haemodynamic load, neurohumoral factors and LA size in the early stages of essential hypertension.

METHODS

We studied 94 consecutive middle-aged subjects, with newly diagnosed stage I-II essential hypertension without left ventricular (LV) hypertrophy and 34 age and sex-matched normotensive individuals. Ambulatory blood pressure (BP) monitoring, plasma levels of brain natriuretic peptide (BNP), metabolic profile and left atrial volume index (LAVI), an echocardiographic measurement of LA volume indexed for the body surface area, constituted the work-up of all subjects.

RESULTS

Hypertensive compared with normotensive subjects had significantly increased office and ambulatory systolic and diastolic BP (P < 0.0001 for all cases) as well as body mass index and waist-to-hip ratio (P < 0.05 for both cases). BNP levels were greater in hypertensive compared with normotensive subjects but were not statistically significant (20.4 versus 17.1 pg/ml, P = NS). Hypertensive compared with normotensive subjects also had significantly increased LV mass index (105 versus 84 g/m, P < 0.0001), LA diameter (39 versus 36 mm, P < 0.0001), and LAVI (22 versus 19 ml/m, P < 0.05). In the hypertensive population, LAVI exhibited significant positive relationships with office systolic BP, ambulatory pulse pressure, LV mass index and BNP. In multiple linear regression analysis only LV mass index and BNP were significantly associated with LAVI (beta = 0.298, P = 0.030 and beta = 0.322, P = 0.009, respectively).

CONCLUSIONS

Increased LAVI, closely associated with LV mass index and BNP, was still found in the early stages of essential hypertension. However, the clinical significance of these findings remains to be elucidated in future studies.

A method for fitting regression splines with varying polynomial order in the linear mixed model

The linear mixed model has become a widely used tool for longitudinal analysis of continuous variables. The use of regression splines in these models offers the analyst additional flexibility in the formulation of descriptive analyses, exploratory analyses and hypothesis-driven confirmatory analyses. We propose a method for fitting piecewise polynomial regression splines with varying polynomial order in the fixed effects and/or random effects of the linear mixed model. The polynomial segments are explicitly constrained by side conditions for continuity and some smoothness at the points where they join. By using a reparameterization of this explicitly constrained linear mixed model, an implicitly constrained linear mixed model is constructed that simplifies implementation of fixed-knot regression splines. The proposed approach is relatively simple, handles splines in one variable or multiple variables, and can be easily programmed using existing commercial software such as SAS or S-plus. The method is illustrated using two examples: an analysis of longitudinal viral load data from a study of subjects with acute HIV-1 infection and an analysis of 24-hour ambulatory blood pressure profiles.