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Biomedical subjects

T G Pickering

Publications and source records attributed to T G Pickering.

At least 145 records · Page 8Linked to original sources
PubMed1992

Relation between job strain, alcohol, and ambulatory blood pressure.

"Job strain" (defined as high psychological demands and low decision latitude on the job) has been previously reported to be associated with increased risk of hypertension and increased left ventricular mass index (LVMI) in a case-control study of healthy employed men, aged 30-60 years, without evidence of coronary heart disease. We hypothesized that job strain would be associated with increased ambulatory blood pressure (AmBP). A total of 264 men at eight work sites wore an AmBP monitor for 24 hours on a working day. In an analysis of covariance model, job strain was associated with an increase in systolic AmBP of 6.8 mm Hg (p = 0.002) and diastolic AmBP of 2.8 mm Hg at work (p = 0.03) after adjusting for age, race, body mass index, Type A behavior, alcohol behavior, smoking, work site, 24-hour urine sodium, education, and physical demand level of the job. Alcohol use also had a significant effect on AmBP. However, among subjects not in high-strain jobs, alcohol had no apparent effect on AmBP at work. Instead, alcohol use and job strain interacted such that workers in high-strain jobs who drank regularly had significantly higher systolic AmBP at work (p = 0.007). Among the other risk factors, only age, body mass index, and smoking had significant effects on AmBP. Job strain also had significant effects on AmBP at home and during sleep as well as on LVMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Cortisol inactivation overload: a mechanism of mineralocorticoid hypertension in the ectopic adrenocorticotropin syndrome.

The more severe mineralocorticoid manifestations in the ectopic ACTH syndrome compared to pituitary Cushing's disease have been attributed to hypersecretion of 11-deoxycorticosterone. Another difference between the two forms of ACTH-excess, however, is a more severe degree of hypercortisolism in the ectopic syndrome. Cortisol can become a potent mineralocorticoid if its peripheral metabolism is interfered with as occurs in the syndrome of apparent mineralocorticoid excess. This mechanism also occurs in an experimental model of the apparent mineralocorticoid excess syndrome induced by licorice derivatives. We have tested the hypothesis that cortisol is a major mineralocorticoid in the ectopic ACTH syndrome because of two factors, marked hypersecretion and incomplete peripheral metabolism of cortisol as a result of an overload of metabolizing enzymes. Two measures of the peripheral metabolism of cortisol were found to be markedly decreased in two patients with the ectopic ACTH syndrome. The cortisol turnover quotients were 17.2 and 19.6 (normal = 215 +/- 98) and the ring A reduction constants were 11.8 and 13.8 (normal = 101 +/- 23). These values were comparable to that found in the syndrome of apparent mineralocorticoid excess and consistent with the hypothesis that cortisol is a significant functioning mineralocorticoid in the ectopic ACTH syndrome.

ACTH Syndrome, Ectopic↗
PubMed1992

Non-invasive measurements of arterial compliance in hypertensive compared with normotensive adults.

AIM: To determine differences in arterial compliance attributable to hypertension. METHODS: Since measurements of arterial compliance have tended to vary in the past according to the method used, a new technique comprising carotid ultrasound and simultaneous, calibrated, carotid pressure waveform measurements was tested in 43 hypertensives and 43 control subjects matched for age, gender and body size. RESULTS: There was a significant reduction in compliance among the hypertensive patients, as estimated by the elastic modulus and the ratio of stroke volume to pulse pressure. However, when the non-linearity of the pressure-volume relationship and the impact of distending pressure were taken into account, by the arterial stiffness index and by the increase in arterial wall thickness associated with hypertension by Young's modulus, there were no significant differences in arterial compliance between the two groups.

Adult↗
PubMed1991

Elevation of ambulatory systolic blood pressure in hypertensive smokers. A case-control study.

Although smoking raises blood pressure, the office blood pressure measurements of smokers are the same as, or lower than, those of nonsmokers. To resolve this paradox, we compared the office and 24-hour ambulatory blood pressures of 59 untreated hypertensive smokers with 118 nonsmoking hypertensives matched for age, sex, and race. The office blood pressures of the smoking and nonsmoking groups were 141/93 and 142/93 mm Hg, respectively. The awake ambulatory systolic blood pressure was significantly higher in the smokers (145 vs 140 mm Hg). This difference was greater among patients over the age of 50 years (153 vs 142 mmHg), and absent among patients under 50 years (140 vs 139 mm Hg). Blood pressures during sleep did not differ between the two groups (121/76 vs 123/77 mm Hg). We conclude that, among white hypertensives above the age of 50 years, smokers maintain a higher daytime ambulatory systolic blood pressure than nonsmokers even though blood pressure measured in the office is similar.

Adult↗
PubMed1991

Ambulatory blood pressure monitoring: assessing the diurnal variation of blood pressure.

The purposes of this paper are to examine the effects of activity, situation of measurement, mood, and occupation on the daily variation of blood pressure and to discuss the potential utility of ambulatory blood pressure monitoring in physical anthropological studies. The subjects of the blood pressure variability study are 125 men who were referred to the Hypertension Center at New York Hospital--Cornell Medical Center for evaluation of hypertension. There were 1,386 blood pressure measurements from these subjects available for study, which were taken using noninvasive ambulatory blood pressure monitoring techniques. Pressures were transformed to z scores using the subject's daily mean pressure and standard deviation to assess the relative elevation during the experience of the various factors. The results show that activity and mood are the most significant sources of blood pressure variation (P less than .005) and are additive. Occupation, which may be an indicator of social class in this population, also modified the mood effects. Because ambulatory blood pressure monitors obtain many readings over a day under a variety of circumstances, their use can improve epidemiological and human biological studies of the inheritance and variability of blood pressure. Ambulatory blood pressure monitoring is an important new tool in the study of human biological variation.

Affect↗
PubMed1991

Captopril renography in the diagnosis of renal artery stenosis: accuracy and limitations.

PURPOSE: The purpose of this study was to determine the sensitivity, specificity, and clinical usefulness of renography performed in combination with captopril administration ("captopril renography") in diagnosing renal artery stenosis. PATIENTS AND METHODS: Fifty-five patients with suspected renal artery stenosis underwent renography prior to performance of renal angiography. Renography was performed on two consecutive days using technetium-99m-diethylenetiamine pentaacetic acid (DTPA) as an index of glomerular filtration rate and iodine-131-orthoiodohippurate (OIH) as an index of renal blood flow. Captopril (25 mg orally, crushed) was administered 1 hour before the second study. Renal artery stenosis was defined as a stenosis exceeding 70%. Renographic criteria were then established, retrospectively, to differentiate renal artery stenosis from essential hypertension based on (1) asymmetry of function and (2) the presence of captopril-induced changes. RESULTS: Renal artery stenosis was detected in 35 of 55 patients (21 with unilateral and 14 with bilateral stenosis). Three criteria were established for diagnosing renal artery stenosis: (1) a percent uptake of DTPA by the affected kidney of less than 40% of the combined bilateral uptake, (2) a delayed time to peak uptake of DTPA, which was more than 5 minutes longer in the affected kidney than in the contralateral kidney, (3) a delayed excretion of DTPA, with retention at 15 minutes, as a fraction of peak activity, more than 20% greater than in the contralateral kidney. The presence of one or more of these criteria was diagnostic of renal artery stenosis, with a sensitivity and specificity of 71% and 75%, respectively before captopril administration, and 94% and 95% after captopril administration. Lesser degrees of asymmetry (i.e., uptake of 40% to 50%) had very poor diagnostic specificity. Among patients with bilateral stenoses, asymmetry identified the more severely affected kidney, but the presence or absence of stenosis in the contralateral kidney could not be reliably determined. When pre- and post-captopril studies were compared, the presence of captopril-induced scintigraphic changes was a highly specific finding for renal artery stenosis, but occurred in only 51% of the cases. OIH scintigraphy provided similar results, with slightly lower sensitivity and specificity. CONCLUSION: Asymmetry of DTPA uptake, time to peak uptake, or retention seen on a single post-captopril renogram is a highly sensitive and specific finding in detecting renal artery stenosis but does not distinguish unilateral from bilateral disease. If renograms are obtained both before and after captopril administration, the presence of captopril-induced change is a highly specific finding for the detection of renal artery stenosis, but the sensitivity of this finding is low.

Antihypertensive Agents↗
PubMed1991

The use of angiotensin converting enzyme inhibitors in combination with other antihypertensive agents.

Angiotensin converting enzyme (ACE) inhibitors have additive effects with most other antihypertensive agents, but the mechanisms of these interactions vary. With diuretics the interaction with ACE inhibitors can be explained by their contrasting effects on the renin-angiotensin system, while with calcium antagonists it may be attributed to independent mechanisms of action. With beta-blockers there is a variable additive effect, which has been proposed to be due to more complete blockade of the renin-angiotensin system than can be obtained with either type of agent alone.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1991

A multicenter evaluation of the A&D TM-2420 ambulatory blood pressure recorder.

The A&D TM-2420 (A&D Engineering, Milpitas, CA) is an automatic, portable, noninvasive blood pressure (BP) recorder which uses a dual microphone system for the detection of Korotkoff sounds. Its accuracy and clinical performance were assessed in a multicenter study that also addressed issues such as observer agreement and the effects of age, arm circumference, heart rate, posture, and blood pressure level on the observer-device differences. We compared 906 simultaneous, same-arm BP measurements in 151 subjects using the TM-2420 versus two skilled clinicians per site using a teaching stethoscope. The agreement between the TM-2420 and mercury column determinations were within 10 mm Hg for 86 to 91% of systolic readings and 91 to 94% of diastolic readings, depending on the posture; a level of agreement which would receive a 'B+' grade from the recent British Hypertension Society guidelines. The limits of agreement (2 standard deviations about the mean difference) for systolic BP between observers and the TM-2420 tended to be greater for the standing position (-20 to 15 mm Hg) compared to supine (-14 to 12 mm Hg) and seated (-13 to 8 mm Hg) positions. Limits of agreement between the observers and device were not dependent upon age, heart rate, arm size, or blood pressure level. Twenty-four-hour blood pressure monitoring in two of the four centers demonstrated an error code rate of 3.4%, excluding 'retries' that are one of the device's features. These data demonstrate an acceptable level of accuracy and performance of the sixth generation of the TM-2420 for use in clinical practice and research.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Challenge response predictors. General principles.

Environmental challenges offer a potential method for predicting hypertension. They could be nutritional (eg, an increased salt load), behavioral (eg, a mental arithmetic task), or physical (eg, an exercise test) in nature. An ideal challenge test should be simple to administer, easily standardized, and with a response that can be precisely quantified. The response is best expressed as a change score from the baseline level, and should be reproducible over time. For the prediction of hypertension, blood pressure is the usual response measure, although others, such as heart rate, are possible. The response should have predictive value independently of other known predictors, including the baseline level. The dependent variables might be future blood pressure, target organ damage, or morbid events.

Behavior↗
PubMed1991

Ambulatory blood pressure variation is related to plasma renin activity in borderline hypertensive men.

The purpose of this study was to examine the relationship between the variability of awake ambulatory blood pressure and the level of plasma renin activity (PRA) in age-matched samples of untreated hypertensive white men. The ambulatory pressures of 376 men (145 under 45 years of age, 231 over 45) were compared across three levels of PRA: less than 1.0 ng/mL/h, 1.0 to 4.0 ng/mL/h and 4.0 ng/mL/h or greater. The results showed that the average diastolic pressure declined with PRA, particularly in men under 45 (95 to 89; P less than .05), but that among the men 45 and older there was a strong, positive relationship between awake diastolic pressure variability and the level of PRA (p less than .001). These results may have important clinical implications since both higher PRA and greater blood pressure variability have been associated with a greater cardiovascular disease risk.

Adolescent↗
PubMed1991

Characterization of auscultatory gaps with wideband external pulse recording.

Three types of auscultatory gaps, called G1, G2, and G3, that occur during blood pressure measurement have been identified by using wideband external pulse recording. We have previously shown that the wideband external pulse recorded during cuff deflation can be separated into three components (K1, K2, and K3), one of which (K2) is closely related to the Korotkoff sound. G1 occurs with cuff pressure just below systolic and is characterized by the presence of K1 and K2 with intermittent disappearance of K2. G1 gaps are related to a phasic decrease of arterial (systolic) pressure and were exhibited by 13 of 60 hypertensive patients. G2 gaps are related to a phasic increase of arterial (diastolic) pressure, occur when cuff pressure is just above diastolic, and are characterized by the presence of K1, K2, and K3 with intermittent disappearance of K2. Seven of 60 hypertensive patients exhibited a G2 gap. G3 gaps occur with cuff pressure between systolic and diastolic and are characterized by an underdeveloped or blunted K2 signal. Three of 60 hypertensive patients exhibited a G3 gap. The identification of auscultatory gaps in relation to the wideband external pulse provides a qualitative measure of their existence, can be of significant value in better understanding aspects of the auscultatory blood pressure measurement technique, and provides an objective basis with which to better understand the mechanisms that cause them.

Auscultation↗
PubMed1991

Ambulatory blood pressure monitoring in clinical practice.

Ambulatory blood pressure monitoring provides a more reliable estimate of blood pressure and its diurnal variability than casual blood pressure measurement. However, the data supporting the link between cardiovascular risk and blood pressure are based almost entirely on casual, or office-based, blood pressure readings, and this form of measurement continues to be the primary factor in clinical decision making. In recent years, compelling evidence from research centers around the world has shown that ambulatory blood pressure measurements correlate more closely with the target organ complications of hypertension and predictions of future cardiovascular events than either casual office or home blood pressure measurements. Improvements in the technology have resulted in ambulatory blood pressure monitors that are increasingly accurate and unobtrusive. As evidence supporting its use continues to mount, the role of ambulatory blood pressure monitoring in clinical medicine can be expected to increase significantly.

Blood Pressure↗
PubMed1991

The normal hourly variation of blood pressure in women: average patterns and the effect of work stress.

The purpose of this study was to examine the pattern of diurnal variation of blood pressure in normotensive working women, and to assess the effect of work stress on this pattern. The subjects were 121 normotensive (based on clinic readings less than 140/90 mmHg) young women (age = 30.2 +/- 7.3 years; range 20-50) who wore an ambulatory blood pressure monitor on a workday from 9 am to 6 am the next day. The effect of work stress on the pattern of variation was assessed by comparing the hourly averages among women who perceived greater stress at work on the day of study ('work stressed') (n = 67) with those of women who perceived greater or equal stress at home on the day of study ('home stressed') (n = 54). The results showed that the systolic pressure of 'work stressed' women was 5-8 mmHg higher (P less than 0.05) and diastolic 3-4 mmHg higher (P less than 0.05) than 'home stressed' women for nearly every hour from 9 am to 6 pm. From 7 pm to 6 am, both groups were similar hour by hour. These data suggest that there is no intrinsic pattern of diurnal blood pressure variation (other than an awake-sleep cycle) in working women. The data also provide a reference standard for comparison with hypertensive women.

Adult↗
PubMed1991

Can behavioural factors produce a sustained elevation of blood pressure? Some observations and a hypothesis.

A major problem confronting behavioural theories of hypertension, such as the reactivity hypothesis, is that stress is likely to be intermittent, whereas the early stages of hypertension appear to be characterized by an increase in the tonic level of blood pressure and sympathetic activity. Furthermore, intermittent sympathetic arousal (e.g. exercise, thigh-cuff compression) does not necessarily raise tonic blood pressure. A worksite-based study of occupational stress has indicated that people in high-stress jobs have increased blood pressure throughout the day and night, which is at least consistent with a behaviourally mediated resetting of the tonic blood pressure level. There is evidence that adrenaline is preferentially released in response to behavioural stresses. According to the 'adrenaline hypothesis', adrenaline can raise tonic blood pressure while noradrenaline does not. We therefore propose that the different long-term effects of behavioural stress and exercise on blood pressure can be explained by their differing effects on catecholamine release.

Blood Pressure↗
PubMed1991

Relationship between the level, pattern and variability of ambulatory blood pressure and target organ damage in hypertension.

Certain forms of preclinical cardiovascular disease are critical to the transition between hypertension and the development of cardiovascular morbid events. The level of the echocardiographic left ventricular mass is a stronger predictor of death or non-fatal events than arterial pressure or any other risk factor except advancing age. While the evidence shows a closer relationship between ambulatory compared with clinic blood pressure measurements and left ventricular mass or other measures of hypertensive disease, it is not clear which measures of ambulatory blood pressure are the most important. Present evidence weakly favors systolic over diastolic ambulatory pressure and daytime over night-time pressures. Further studies of large, well defined populations with standardized components of ambulatory blood pressure and well validated measures of hypertensive target organ damage are needed.

Blood Pressure↗