Ambulatory blood pressure monitoring: practical considerations

Emerging Role of Translational Digital Biomarkers Within Home Cage Monitoring Technologies in Preclinical Drug Discovery and Development

In drug discovery and development, traditional assessment of human patients and preclinical subjects occurs at limited time points in potentially stressful surroundings (i.e., the clinic or a test arena), which can impact data quality and welfare. However, recent advances in remote digital monitoring technologies enable the assessment of human patients and preclinical subjects across multiple time points in familiar surroundings. The ability to monitor a patient throughout disease progression provides an opportunity for more relevant and efficient diagnosis as well as improved assessment of drug efficacy and safety. In preclinical in vivo animal models, these digital technologies allow for continuous, longitudinal, and non-invasive monitoring in the home environment. This manuscript provides an overview of digital monitoring technologies for use in preclinical studies including their history and evolution, current engagement through use cases, and impact of digital biomarkers (DBs) on drug discovery and the 3Rs. We also discuss barriers to implementation and strategies to overcome them. Finally, we address data consistency and technology standards from the perspective of technology providers, end-users, and subject matter experts. Overall, this review establishes an improved understanding of the value and implementation of digital biomarker (DB) technologies in preclinical research.

Hypertensive patients show delayed wound healing following total hip arthroplasty

BACKGROUND

Prolonged wound-discharge following total hip arthroplasty (THA) is associated with an increased risk of infection. However, the potential role of hypertension in prolonging the duration of wound healing in this population has not yet been investigated. The aim of the present study was to compare healing in this population that has not yet been investigated. The aim of the present study was to compare hypertensive and normotensive THA patients in terms of the length of time required to achieve a dry wound and the length of stay in the hospital.

METHODS

One hundred and twenty primary THA patients were evaluated. Pre-operative clinical history and physical examination revealed that 29 were hypertensive and 91 were normotensive. The two groups were statistically matched using optimal propensity score matching. The outcomes of interest were the number of days until a dry wound was observed and the duration of hospital stay.

RESULTS

The average systolic blood pressures were 150.1 mmHg and 120.3 mmHg for the hypertensive and normotensive groups, respectively. The mean number of days until the wound was dry was 3.79 for the hypertensive group and 2.03 for the normotensive group. Hypertensive patients required more days for their wounds to dry than normotensive patients (odds ratio  =  1.65, p<0.05). No significant difference in the duration of hospital stay was found between the two groups.

CONCLUSIONS

Hypertensive patients had a higher risk of prolonged wound discharge after THA than their normotensive counterparts. Patients with prolonged wound drainage are at greater risk for infection. Clinicians should pay particular attention to infection-prevention strategies in hypertensive THA patients.

Role of plasma aldosterone concentration in regression of left-ventricular mass following antihypertensive medication

BACKGROUND

Aldosterone is known to bring about damage to various organs; however, it is unclear how important the changes in plasma aldosterone concentration (PAC) are as contributors to regression of left-ventricular (LV) mass in hypertensive patients following long-term treatment with calcium channel blockers (CCBs) or angiotensin II receptor blockers (ARBs).

OBJECTIVE

To assess the importance of changes in PAC during antihypertensive treatment.

METHODS

Forty-four untreated hypertensive patients were randomly assigned to either CCB (amlodipine) group or ARB (losartan) group. In addition to PAC measurements LV geometry was echocardiographically assessed with LV mass index (LVMI) and relative wall thickness (RWT) before and 6 and 12 months after treatment.

RESULTS

Reduction of systolic blood pressure (SBP) in 12 months was greater in the CCB group than in the ARB group (-19 ± 8 vs. -11 ± 15%, P < 0.05 as percentage reduction from the values before treatment). PAC decreased in 12 months in the ARB group but not in the CCB group (-31 ± 31 vs. 17 ± 53%, P < 0.01 as percentage reduction from the values before treatment). Larger percentage drop in PAC was associated with larger percentage reduction of LVMI (r = 0.45, P < 0.01 for all). Multiple step-wise regression analysis showed that the percentage reduction of LVMI is related to the percentage changes in SBP and the percentage changes in PAC (r = 0.46, P < 0.01).

CONCLUSION

Regression of LV mass was the larger in patients with the greater decrease in PAC associated with antihypertensive medication regardless of CCB or ARB. Changes in PAC and SBP may be key determinants of regression of LV mass in hypertensive patients regardless of the medication selected.

Exclusion of Influence of Physical Activity on Ambulatory Blood Pressure

OBJECTIVE

The basal blood pressure (BP) is more intimately related to hypertension severity than casual BP. BP values obtained by ambulatory blood pressure monitoring (ABPM) tend to be influenced by patients' physical activity because values are not always obtained with the patient at rest. The purpose of this study was to estimate the influence of physical activity on BP and determine daytime BP adjusted for activity as measured by ABPM.

METHODS

This study targeted three clinically different groups: healthy medical students (HS, n = 40), patients with hypertension (HT, n = 20), and patients with diabetes mellitus (DM, n = 7). The subjects' BP, heart rate (HR), and physical activity level were measured by a noninvasive portable multi-biomedical recorder. To identify the influence of physical activity on BP in the three study groups, a least squares regression analysis of the relation between BP and ACT (an index of activity with acceleration) was performed for each group.

RESULTS

ACT had a positive influence on systolic BP (SBP) in the HS, HT, and DM groups (R2 = 0.319, 0.576, 0.697, respectively). SBP adjusted for ACT (walking level) by means of the regression model with dummy variable was 0-24 mmHg lower than the value of SBP measured by ABPM, and daytime SBP (walking level) was overestimated by approximately 10 mmHg in comparison to the value of SBP at rest (ACT = 0).

CONCLUSION

Physical activity had a positive effect on SBP. The results showed that physical activity (walking-level) had a positive effect on SBP of about 10 mmHg.

How stable is postural hypotension in the general aged population?

Although postural hypotension (PH) is a common clinical symptom in the elderly, nothing is known of its stability in the long run. To investigate this issue we carried out a prospective cohort study in a general aged population as a part of Helsinki (Finland) Aging Study. Random persons of three age cohorts (75-, 80- and 85-years, n = 274) were followed for 5 years. Blood pressure (BP) was measured at supine and standing positions both at entry and after 5 years. Both supine and standing BP levels decreased during 5-year follow-up but the prevalence of PH (decrease in systolic BP > 20 mmHg or that in diastolic BP > 10 mmHg) remained virtually unchanged (28% at entry - 26% after 5 years). There were, however, marked differences in the distributions of individuals in the different categories of PH and only 25.8% of subjects fulfilled the same criteria at 5 years. Only 9% of subjects had significant falls in SBP and DBP both at entry and after 5 years. These persons were characterized by no other clinical features than higher initial supine BP levels. In conclusion, this study shows the instable nature of PH during the 5-year follow-up in the general aged population and challenges the use of blood pressure changes as a sole diagnostic criteria of PH in epidemiological studies.

alpha-Adducin Gly460Trp polymorphism is associated with low renin hypertension in younger subjects in the Ohasama study

BACKGROUND

The Gly460Trp polymorphism of the alpha-adducin gene (ADD-1 ) has been examined as a candidate gene for essential hypertension with salt sensitivity in the Caucasian population. However, we failed to detect a positive association between the Gly460Trp polymorphism of ADD-1 and hypertension in a small series of Japanese subjects.

OBJECTIVE

To examine the precise association between the Gly460Trp polymorphism of ADD-1 and blood pressure (BP), we carried out an association study using a Japanese population: the Ohasama Study.

DESIGN

Subjects (n = 1490) were recruited from participants in the Ohasama Study, which is a cohort in a rural community of northern Japan.

METHODS

DNA was extracted from the buffy coat of the participants who gave informed consent for genetic analysis, and the Gly460Trp polymorphism of ADD-1 was determined by the TaqMan polymerase chain reaction method. Various BP values (casual BP, ambulatory BP and home BP) were measured in the Ohasama study. We used the mean values of these BP measurements for analysis.

RESULTS

The frequencies of genotypes in the Ohasama population were 23% Gly/Gly, 49% Gly/Trp, and 28% Trp/Trp. In the baseline characteristics, age, sex, body mass index, frequency of diabetes and hyperlipidemia were significantly different between hypertensive or normotensive subjects. In total subjects, all BP values were not different among genotypes. In the younger subjects ( 60 years old) with low plasma renin activity (< 1.0 ng/ml per h), however, ambulatory BP and home BP were significantly higher in the subjects with the Gly/Trp or Trp/Trp genotypes of ADD-1 polymorphism than in those with the Gly/Gly genotype. In the same population, the frequency of the Gly/Trp or Trp/Trp genotypes of was significantly higher in hypertensives than in normotensives (83 versus 72%, chi1(2) = 4.04, P<0.05; odds ratio, 2.12; 95% confidence interval, 1.02-4.68).

CONCLUSIONS

These findings suggest the possibility that the Gly460Trp polymorphism of ADD-1 is associated with low renin hypertension.

Blood pressure responses after carotid surgery: relationship to postoperative baroreceptor sensitivity

BACKGROUND AND PURPOSE

Among hypertensive patients after carotid surgery, a group of patients with increased baroreflex sensitivity was identified. In the other group of hypertensive patients, blood pressure and reflex sensitivity were unchanged postoperatively. We hypothesized that a partial readjustment of baroreceptor sensitivity would produce more stable blood pressure profiles.

METHODS

In order to test this hypothesis, a prospective, long-term follow-up study was designed. Blood pressure was monitored in 18 hypertensive and 6 normotensive patients during 6 months using a self-measurement technique. In addition, continuous 24-hour blood pressure monitoring was performed 6 months after surgery. The mean values and the ranges (amplitudes) of systolic and diastolic blood pressure were calculated as indicators for the stability of the circulatory system.

RESULTS

Hypertensive patients with unchanged postoperative baroreceptor sensitivity showed significantly more pronounced instabilities of their blood pressure profiles (amplitudes of systolic and diastolic blood pressure p < 0.05 to p < 0.001). A relationship between baroreceptor function and antihypertensive therapy could also be demonstrated, with adequate therapy being much more difficult in patients with reduced or unchanged baroreceptor sensitivity.

CONCLUSIONS

In contrast to vascular surgery on the aorta or in the region of the lower limbs, carotid surgery is frequently associated with blood pressure changes, demonstrating the essential role of the baroreceptors in the carotid sinus for the regulation of postoperative blood pressure. Since it seems to be the variability of blood pressure, and not the blood pressure level alone, that is critical, close blood pressure monitoring--allowing for an assessment of blood pressure variability--appears to be of particular importance in such patients.

Fosinopril monotherapy: relationship between blood pressure reduction and time of administration

The time to peak antihypertensive effect and the trough-to-peak ratio were determined in 64 Caucasian patients (19 men, 45 women) with mild to moderate hypertension [supine diastolic blood pressure (DBP) 95 to 115 mmHg]. They received placebo or fosinopril 10, 20, or 40 mg once daily for 4 weeks. The study consisted of a 4-week placebo lead-in, 4 weeks' double-blind treatment, and a 1-week placebo washout period. Vital signs were determined biweekly before dosing, and blood pressures were measured every 1 to 2 h during two 27-h periods at the beginning and end of treatment. After the first and last doses of all three regimens, the peak effect on blood pressure occurred 5 to 7 h after all three dosages. Neither peak nor trough blood pressure changes showed a clear dose-response relationship. Trough to peak ratios for the first dose, corrected for placebo effects, were 79% for fosinopril 10 mg, 48% for fosinopril 20 mg, and 74% for fosinopril 40 mg, and the trough-to-peak ratios for the last dose were 41% for fosinopril 10 mg, 32% for fosinopril 20 mg, and 44% for fosinopril 40 mg. In the 38 responders among the 48 patients receiving fosinopril (supine DBP decrease of at least 5 mmHg at 24 h postdose), trough-to-peak ratios ranged from 50 to 81%, and the range indicates that fosinopril is efficacious when administered once daily. Adverse effects were mild to moderate, and no patient discontinued treatment. Changes in the laboratory test results, electrocardiograms, or the results of physical examinations were unremarkable.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood pressure and heart rate relationship in normotensive and hypertensive subjects

A twenty-four-hour blood pressure (BP) monitoring was performed in 20 normotensive and 20 hypertensive subjects, matched by sex and age. Blood pressure and heart rate (HR) variability were evaluated both as absolute and percent standard deviation. In agreement with the literature no significant difference in HR and BP variability was observed between the two groups. The linear regression between HR and BP values was evaluated in both groups. The authors observed a significant difference in the relationship between these two cardiovascular variables between the two groups. In the hypertensive group the cardiovascular control of HR and BP showed a different relationship than in normotensive subjects, suggesting a different neurovegetative modulation.

Childhood blood pressure tracking correlations corrected for within-person variability

The correlation coefficient between initial and subsequent blood pressure (BP) measurements is referred to as the tracking correlation. Childhood BP tracking correlations, although positive, have been considered too low to make accurate predictions for an individual. These correlations, however, can be raised substantially by averaging BP over multiple weekly visits in each year, which partially accounts for within-person variability. In a cohort of 333 school children, we measured BP 3 times on each of 4 successive weekly visits, in each of 4 consecutive years, using a random-zero sphygmomanometer. Approximately 90 per cent of subjects had data for one or more follow-up years, and 75 per cent of subjects who entered in the first year had data for all four years. With a model that allows estimation of correlations and that uses all available longitudinal data, we calculated tracking correlations completely corrected for within-person variability, the statistical equivalent of measuring BP on an infinite number (infinity) of visits and measurements per visit. Age-sex adjusted tracking correlations for 3 years of follow-up based on the means from 1,2,3,4, and infinity visits are, for systolic BP, 0.43, 0.56, 0.62, 0.66, and 0.73, respectively, and for diastolic BP, 0.20, 0.37, 0.46, 0.50, and 0.70, respectively. With longer follow-up, the use of corrected tracking correlations would allow determination of the maximal extent to which childhood BP can predict adult levels, and therefore the usefulness of screening to identify children at high risk of developing hypertension.

Left ventricular hypertrophy

OBJECTIVE

To review the pathophysiology, epidemiology, patterns, diagnosis, and treatment of left ventricular hypertrophy with emphasis on the elderly.

DATA SOURCES

A computer-assisted search of the English-language literature (MEDLINE database) followed by a manual search of the bibliographies of pertinent articles.

STUDY SELECTION

Studies on the pathophysiology, epidemiology, patterns, diagnosis, and treatment of left ventricular hypertrophy were screened for review. Studies on left ventricular hypertrophy in the elderly and recent studies were emphasized.

DATA EXTRACTION

Pertinent data were extracted from the reviewed articles. Emphasis was on studies involving the elderly. Relevant articles were reviewed in depth.

DATA SYNTHESIS

Available data about the pathophysiology, epidemiology, patterns, diagnosis, and treatment of left ventricular hypertrophy with emphasis on studies involving the elderly were summarized.

CONCLUSIONS

Left ventricular hypertrophy caused by hypertension or other cardiovascular disease is not only a marker for but also a contributor to cardiovascular morbidity and mortality in elderly and young patients. The question of whether regression of left ventricular mass in patients with hypertension will decrease cardiovascular morbidity and mortality needs to be answered by prospective studies using different types of antihypertensive drugs. Future studies on the efficacy of antihypertensive drugs and on stratification of therapy should include echocardiographic estimates of left ventricular mass index.

Efficacy of 24-hour ambulatory blood pressure monitoring in children

OBJECTIVES

To determine whether the use of an ambulatory blood pressure monitor (ABPM) is feasible and gives accurate readings in children, and to provide data on normal daily blood pressures (BPs) and BP patterns in children.

DESIGN

Cohort.

SUBJECTS

Ninety-nine healthy fifth-grade students.

INTERVENTIONS

Students wore an ABPM for 24 hours while recording their activities in diaries. Before and after the study period, each subject had three BPs simultaneously measured with the ABPM and a mercury manometer to assess the accuracy of the ABPM. An activity scale was retrospectively applied to diary entries to help explain the variety of BP patterns noted during data analysis.

RESULTS

Systolic BPs obtained with the ABPM at the beginning and end of the study were slightly higher than those obtained with a mercury manometer; diastolic BPs were virtually identical. A circadian pattern of BPs was noted: mean systolic and diastolic BPs were higher during the day than at night. The BP patterns ranged from "hypoactive" (little baseline variation) to "hyperactive" (wide fluctuations with spikes to elevated BP ranges) during various activities. In general, higher BPs were noted at times of increased activity or emotional levels.

CONCLUSIONS

Ambulatory BP monitoring was well tolerated, and measurements were reproducible and accurate. The variety of BP measurements noted at different activity levels indicate that a child's activity should be considered during data analysis. As further experience is gained, the ABPM should prove helpful in diagnosis and management of hypertension in children.

Measurement of blood pressure in the obese

There is a need for caution in measuring blood pressure in the obese. Problems related to adequate cuff-bladder size and shape are apparent from a review of the literature. Imperfections in experiments comparing intra-arterial/indirect blood pressure measurements remain. Cuff characteristics, as well as cuff-bladder width and length, can bias measurement of blood pressure in the obese. Authoritative committee recommendations and the differing needs of blood pressure measurement in obese adults and children still need to be rationalized. Manufacturing faults of cuff bladder and cuff availability continue to be a problem for blood pressure measurement in the obese. Measurement of blood pressure in large obese and large muscular arms may require different adjustments for cuff width and arm circumference. Nomograms for adjusting blood pressure recording in the obese are inadequate. The most important adjustment for measuring blood pressure in the obese derives from choosing the correct cuff width-arm circumference (CW/AC) ratio. Such action reduces the intersubject variability of blood pressure measurement in clinical and epidemiologic studies. Past studies probably overestimated blood pressure level in the obese and so underestimated the risk of elevated blood pressure in the obese.

Circadian blood pressure pattern in patients with treated hypertension and left ventricular hypertrophy

Left ventricular hypertrophy in hypertensives is an important determinant of prognosis. In the present study 45 patients with treated essential hypertension were divided into two groups: 23 patients had normal left ventricular dimension and 22 patients had echocardiographic signs of left ventricular hypertrophy (LVH). All patients were adequately treated during daytime, but ambulatory blood pressure monitoring showed a distinct abnormal pattern in the LVH group characterized by a lack of blood pressure reduction during the night; 16 of 22 patients with LVH had no blood pressure decline during the night, whereas 17 of 23 patients without hypertrophy showed this reduction (P less than 0.01). In conclusion, patients with hypertension and LVH often reveal a lack of blood pressure decline during the night, which may be the reason for the development of left ventricular hypertrophy (and thus should be managed by a different circadian blood pressure therapy) or which may be the consequence of progressive structural changes in the resistance vessels, along with the development of left ventricular hypertrophy. It is suggested that patients with hypertension and left ventricular hypertrophy should have ambulatory twenty-four hour blood pressure monitoring.

Effects of different once-a-day medications on 24-hour blood pressure recordings in hypertensives

Compliance with antihypertensive treatment can be increased by using medications that are taken only once daily. There is, however, concern as to whether the efficacy of such drugs is sufficient to cover 24 h. Ambulatory blood pressure monitoring (ABPM) is an ideal technique to assess the effect of this kind of drug and to determine over- or undertreatment. In this study three drugs were examined as once-a-day preparations. Thirty-six patients were treated with three different doses of bisoprolol, as an example of the beta 1-selective beta-blockers; 12 patients were treated with a combination of the AChE-inhibitor enalapril and hydrochlorothiazide; eight patients were treated with nifedipine once per day, a new galenic form of nifedipine, as an example of the calcium-channel blockers. In each group we saw a significant downward shift over the entire 24-h curve. Our results also show that using 24-h blood pressure monitoring devices can help establish an appropriate dose, avoid over- and undertreatment, and control the total burden of the patient.