Biomedical subjects
T G Pickering
Publications and source records attributed to T G Pickering.
Measurement reliability of cardiovascular reactivity change scores: a comparison of intermittent and continuous methods of assessment.
Cardiovascular reactivity testing is a widely used measure of risk for hypertension and coronary heart disease. Evidence for the reliability of the measures, however, is weak. If the measures (usually change scores) are unreliable, the usefulness of testing is limited, since relationships with other measures, such as disease outcomes, may be obscured. This study examines the reliability of blood pressure change, using both a traditional method of assessment (Colin ABPM) which provides intermittent readings, and a non-invasive method that samples the complete distribution of pressures (Ohmeda Finapres). While the reliability for the Colin was found to be good for absolute level of individual measurements, it was extremely poor for change scores. The Finapres, however, yielded high reliabilities for change scores as well as absolute levels, due to the large number of readings taken during baseline and stressor conditions. Implications for reactivity testing methodology are discussed.
Validating ambulatory blood pressure monitors.
Explore the source record for details and available documents.
Determinants and consequences of the diurnal rhythm of blood pressure.
The diurnal rhythm of blood pressure (BP) is influenced by both extrinsic and intrinsic factors, with the former usually being of greater significance. Non-dippers, in whom the normal nocturnal fall of pressure is diminished, have been reported to show more target organ damage (left ventricular hypertrophy (LVH)) than dippers, which may be explained by a higher average 24 h BP. Whether or not the pattern of BP (as opposed to the level) also is prognostically important is probable but unproven, given the known morning surge of the incidence of many acute cardiovascular events. The pathological significance of different diurnal patterns of BP change may depend both on the method of analysis and on the outcome measure used.
The influence of behavioral factors on the daily variation of blood pressure.
Blood pressure (BP) changes continually throughout the day and night in response to changes in activity and in the environment. Behavioral influences include posture, physical and mental activity, and emotional state. The absolute magnitude of these influences may show consistent differences according to demographic factors such as gender and environment (eg, at work or at home). Occupational stress appears to have a greater effect on the BP in men than in women, while domestic stress (eg, the number of children) influences BP more in women. Ambulatory BP recordings should be interpreted according to the behavioral setting in which they are made.
A comparison of ambulatory blood pressure and heart rate at home and work on work and non-work days.
OBJECTIVES: First, to test whether there was a change in the blood pressure and heart rate on work days relative to non-work days; secondly, to assess whether there were work-home differences on these days; and, thirdly, to assess whether these changes were similar in both normotensives and hypertensives. DESIGN AND SUBJECTS: Twenty-four working men (17 mild hypertensives and seven normotensives) wore an ambulatory blood pressure monitor for two 24-h periods (at work and home), on a work day ('on day') and on a non-work day ('off day'). METHODS: Means were calculated for each day for each home and work period. On the off day, the 'work' mean was defined using the readings during the usual working hours. To control for the effect of position on the means, statistical procedures that control for position were employed. These means were then analyzed by repeated-measures analysis of variance with two within-person factors. Period (home-work) and Day (on-off), and one between-person factor, Hypertensive Status (mild hypertensive-normotensive). RESULTS: When hypertensives and normotensives were combined, diastolic blood pressure (DBP) was significantly greater at work than at home. However, for both systolic blood pressure (SBP) and DBP this work-home difference was dependent on whether it was the on or the off day, the work-home difference being greater on the work day. Furthermore, the noted work-non-work day changes between work and home were significantly different for DBP for normotensives and mild hypertensives. Normotensives experienced a 6-mmHg decrease in blood pressure on the off day, whereas mild hypertensives had a 3-mmHg average increase on the off day. No significant differences were found in the pattern of work-home differences between on and off days for mild hypertensives and normotensives, although the effect approached significance for SBP, providing an indication that the work-home differences may depend on both hypertensive status and work-non-work day. Heart rate was significantly higher during work than at home. Although normotensives had higher heart rates, the work-home difference was constant across on and off days. Among 10 subjects who agreed to wear the monitor a third time on a second work day, the average work blood pressures during the two work periods were nearly equivalent, arguing against an habituation effect to the monitor. CONCLUSIONS: These data support the notion that, for blood pressure, activity is an important determinant of level. A circadian basis to blood pressure was not supported. We found differences between work and non-work days for normotensives, and a trend towards differences by work-home period and work-non-work day for hypertensives. For heart rate the opposite result was found. Heart rate was affected only by time of day (as denoted by work and home periods) and was stable across on and off days. These results suggest that experimental or statistical control of activity and position may be necessary if ambulatory blood pressure monitoring is to be used as either a diagnostic or research tool.
A test of reproducibility of blood pressure and heart rate variability using a controlled ambulatory procedure.
OBJECTIVE: To determine whether the previously reported poor reproducibility of blood pressure variability measured by ambulatory blood pressure monitoring (ABPM) is due to the uncontrolled nature of physical and mental activity during the monitoring period. DESIGN: ABPM was performed on two separate days during which subjects performed identical activities, accompanied by the experimenter. Thus, activity and posture were controlled, both within and between subjects. Two measures of variability were used: SD and the root-mean-square of successive differences (RMSSD). METHODS: Thirty-seven subjects participated. Each engaged in a series of activities, such as walking outdoors, editing and alphabetizing tasks, and eating lunch, while wearing an A & D 2420 ambulatory blood pressure monitor which took measurements at 5-min intervals. Measures of variability were computed within each session. RESULTS: Contrary to previous reports, reproducibility was moderately high for blood pressure, with significant correlations between SD and between RMSSD for systolic and diastolic blood pressure. Heart rate reproducibility was less good. CONCLUSIONS: Lack of standardization of activities from one occasion to another is a major reason for the poor reproducibility of blood pressure variability when measured using ABPM. Even when activities are standardized, however, the reproducibility of blood pressure variability is still only moderate and may limit the ability of researchers to detect associations between ABPM variability and other measures.
Blood pressure variability and ambulatory monitoring.
The inherent variability of blood pressure means that the accuracy of a small number of clinic readings in estimating the true blood pressure is limited. In many patients, a clinic visit provokes an increase in blood pressure such that they may be misclassified as being hypertensive (white coat hypertension). This applies to about 20% of hypertensives. Ambulatory monitoring has the potential to overcome these limitations. The white coat effect may still occur in patients taking antihypertensive medications, although in some cases medication may lower the clinic pressure without affecting the ambulatory pressure. The diurnal rhythm of blood pressure is another major source of variability and is influenced by both extrinsic and intrinsic factors. Its pathologic significance is unclear. Antihypertensive medication generally lowers the set point of blood pressure but has relatively little effect on variability.
Behavior changes and the prevention of high blood pressure. Workshop II. AHA Prevention Conference III. Behavior change and compliance: keys to improving cardiovascular health.
Explore the source record for details and available documents.
What is normal blood pressure? Comparison of ambulatory pressure level and variability in patients with normal or abnormal left ventricular geometry.
To assess the level and pattern of normal ambulatory blood pressure (ABP) using a non-BP standard to identify normality, we examined the level and variability of ABP during the waking day, at work, at home, and during sleep and looked at physician and technician BP measurements in 191 adults whose left ventricular (LV) geometry was classified by echocardiography. Clinic BPs were similar in the 120 subjects with normal LV geometry and the 35 subjects with concentric LV remodeling. Pressures were only modestly higher in the 15 subjects with concentric LV hypertrophy than in the 21 with eccentric hypertrophy. In contrast, these subject groups differed with regard to their ABPs during the waking hours, at home, and especially at work. However, no difference in BP variability, as assessed by the standard deviation of awake systolic or diastolic BP, existed among the subject groups identified by LV geometric patterns. Comparison of patients with concentric LV hypertrophy, the LV pattern associated with the worst prognosis, with normotensive subjects with normal LV geometry suggests that awake ABPs in adults below 139/86 mm Hg might be considered normal, whereas values over 149/95 mm Hg might be considered pathologic. Verification of these conclusions is needed, however, in larger series and with the use of additional measures of preclinical hypertensive disease.
Detection of renovascular hypertension. State of the art: 1992.
PURPOSE: To review recent advances in detecting renovascular hypertension. DATA SOURCES: Original English-language reports obtained through a MEDLINE search for the years 1987 to 1991. Also, a manual search through Index Medicus as well as bibliographies of original reports and selected review articles. STUDY SELECTION AND DATA EXTRACTION: Cited studies were critically reviewed with emphasis on study size, patient sample, methods, diagnostic criteria, and reproducibility of results. Where applicable, reviews that combined the results of smaller studies are cited. RESULTS: A sensitivity of 74% and a specificity of 89% have been reported for the captopril test and of 93% and 95%, respectively, for captopril scintigraphy with diethylenetriaminepentaacetic acid (DTPA). The sensitivity and specificity of renal vein renin determination are 80% and 62%, respectively and may increase with the use of stricter technical criteria and maneuvers to stimulate renin secretion. These tests differentiate renovascular hypertension from essential hypertension more reliably than from asymmetric renal parenchymal disease; however, they do not reliably distinguish unilateral from bilateral stenosis. Other tests are less widely used. Intravenous pyelography (sensitivity, 74.5%; specificity, 86.2%) has the disadvantages of radiation and dye load exposure. Intravenous angiography is expensive and invasive and does not always enable visualization of the origin of the renal artery. The roles of duplex ultrasound and magnetic resonance angiography remain to be clarified. CONCLUSIONS: Noninvasive tests are cost effective and have a high predictive value in patients with clinical clues suggestive of renovascular hypertension. These tests are not recommended for use in patients with a low likelihood of disease.
The relationship between 'job strain,' workplace diastolic blood pressure, and left ventricular mass index: a correction.
Explore the source record for details and available documents.
Predicting the response to nonpharmacologic treatment in mild hypertension.
Explore the source record for details and available documents.
The impact of anticipation of job loss on psychological distress and worksite blood pressure.
The impact of occupational stressful life events on psychological distress and blood pressure was examined among employees of a major New York City brokerage firm undergoing massive layoffs. One hundred thirty-nine employees of the firm, who had participated in a blood pressure screening in 1986, were rescreened during the period of layoffs within their company in 1989. About two-thirds of the 139 employees reported being "somewhat" or "very" anxious or upset in 1989 during the period of layoffs, and psychological distress was significantly elevated among those employees reporting possible or definite layoff or job change and/or difficulty in obtaining a comparable job. However, we found no increase in overall blood pressure level, and no effect of anticipation of job loss on 1989 blood pressure when controlling for 1986 blood pressure level, age, body mass index, work hours, and other demographic variables. On the other hand, employment in a department sold to another employer on the day of screening, as well as employment in a clerical job title, were both associated with significant increases in diastolic blood pressure of about 5 mm Hg.
Patterns of left ventricular hypertrophy and geometric remodeling in essential hypertension.
The spectrum of left ventricular geometric adaptation to hypertension was investigated in 165 patients with untreated essential hypertension and 125 age- and gender-matched normal adults studied by two-dimensional and M-mode echocardiography. Among hypertensive patients, left ventricular mass index and relative wall thickness were normal in 52%, whereas 13% had increased relative wall thickness with normal ventricular mass ("concentric remodeling"), 27% had increased mass with normal relative wall thickness (eccentric hypertrophy) and only 8% had "typical" hypertensive concentric hypertrophy (increase in both variables). Systemic hemodynamics paralleled ventricular geometry, with the highest peripheral resistance in the groups with concentric remodeling and hypertrophy, whereas cardiac index was super-normal in those with eccentric hypertrophy and low normal in patients with concentric remodeling. The left ventricular short-axis/long-axis ratio was positively related to stroke volume (r = 0.45, p less than 0.001), with cavity shape most elliptic in patients with concentric remodeling and most spheric in those with eccentric hypertrophy. Normality of left ventricular mass in concentric remodeling appeared to reflect offsetting by volume "underload" of the effects of pressure overload, whereas eccentric hypertrophy was associated with concomitant pressure and volume overload. Thus, arterial hypertension is associated with a spectrum of cardiac geometric adaptation matched to systemic hemodynamics and ventricular load. Concentric left ventricular remodeling and eccentric hypertrophy are more common than the typical pattern of concentric hypertrophy in untreated hypertensive patients.
Ambulatory blood pressure and reactivity.
Explore the source record for details and available documents.
The ninth Sir George Pickering memorial lecture. Ambulatory monitoring and the definition of hypertension.
Explore the source record for details and available documents.
Parallel cardiac and vascular adaptation in hypertension.
BACKGROUND: Although vascular damage in the noncoronary circulation is a major cause of complications in hypertension, relatively little is known of the in vivo geometry and function of the arterial circulation in patients with uncomplicated hypertension or of their relation to left ventricular hypertrophy, a marker of enhanced risk of cardiovascular complications. METHODS AND RESULTS: Wall thickness and internal diameter of the common carotid artery and the presence of atherosclerosis within the extracranial carotid arteries were determined by ultrasound in 43 asymptomatic hypertensive patients and 43 normotensive subjects matched for sex, age, and body size. Vascular stiffness was estimated from simultaneous superimposed carotid pressure waveforms obtained with an external solid-state transducer. Left ventricular size and function were determined echocardiographically. Compared with normal subjects, hypertensive patients had greater left ventricular absolute and relative wall thicknesses, left ventricular mass, and carotid absolute and relative wall thicknesses (p < 0.005). Carotid intimal-medial thickness exceeded the 95th percentile of normal values in 28% of hypertensive patients (p < 0.01). Carotid atherosclerosis was equally prevalent within the two blood pressure groups and was associated with older age, larger left ventricular and carotid wall thicknesses, and carotid diameter. Despite similar carotid pulse pressures, vascular stiffness was significantly increased in the hypertensive patients. Among the population as a whole, significant relations existed between cardiac and vascular wall thicknesses and internal dimensions. In multivariate analyses, these relations were statistically independent of age and blood pressure. CONCLUSIONS: The present study documents the presence of geometric and functional changes within the common carotid artery in uncomplicated hypertension that parallel findings within the left ventricle. The potential contribution of these changes to the cardiovascular complications of hypertension, particularly in the setting of left ventricular hypertrophy, is unknown.