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Biomedical subjects

W B White

Publications and source records attributed to W B White.

At least 73 records · Page 4Linked to original sources
PubMed1995

Ambulatory blood pressure monitoring in current clinical practice and research.

As more scientific evidence accumulates concerning the relationship between ambulatory blood pressure and hypertensive organ disease, the technique of ambulatory blood pressure monitoring appears to be gaining a foothold in clinical practice and research. Over the past 2 years, an important follow-up study has revealed that 'white coat' hypertension has a low morbidity compared with sustained hypertension. However, other cross-sectional studies continue to fuel the debate regarding the definition and risks associated with white coat hypertension. The application of ambulatory blood pressure monitoring to clinical hypertension trials remains superior to that of office blood pressure measurements. As further data from other prospective interventional studies are published in the next few years, further definition of the utility of the technique will be possible.

Blood Pressure↗
PubMed1995

Normal-appearing captopril MAG-3 renal scintigraphy in hemodynamically significant renal artery stenosis. A case report.

The finding from a normal-appearing angiotensin converting enzyme (ACE)-inhibitor renal scan is generally reassuring to the physician screening for renovascular hypertension. In fact, the false-negative rate for captopril scintigraphy is very low. Possible reasons for false-negative scans have not been well documented. A fifty-two-year-old man was evaluated and found to have renovascular hypertension on two occasions, at initial presentation and again eight months later (restenosis had occurred). Renovascular hypertension was present on both occasions as judged by decline of blood pressure following angioplasty of right renal artery stenosis (approximately 80% and approximately 70% stenosis on the two occasions, respectively). However, ACE-inhibitor renal scanning with 99mTc MAG-3 gave disparate results on the two occasions. The first study using oral captopril (25 mg) indicated a low probability of renal artery stenosis, whereas the second study done with the patient regularly taking lisinopril (10 mg daily) was markedly positive. Possible reasons for the initial negative study include poor absorption of oral captopril or inadequate inhibition of the renin-angiotensin system by the 25 mg dose.

Captopril↗
PubMed1995

Ambulatory blood pressure monitoring in the evaluation of hypertension therapy.

During the past decade, ambulatory monitoring of the blood pressure has become an important tool for evaluating the pharmacodynamics and clinical efficacy of antihypertensive drugs during development. Furthermore, this methodology aids physicians in practice in the assessment of blood pressure control in many subsets of patients with hypertension.

Blood Pressure Monitoring, Ambulatory↗
PubMed1995

Long-term safety and efficacy of moexipril alone and in combination with hydrochlorothiazide in elderly patients with hypertension.

The purpose of this study was to evaluate the long-term safety and efficacy of moexipril, a non-sulphydryl angiotensin converting enzyme inhibitor, alone or in combination with hydrochlorothiazide in older patients with hypertension. One hundred and seventy two hypertensive men and women, 65-80 years old, with seated DBP between 95 and 114 mm Hg were studied. The study was a 2 year, multicentre (12 centres), open-label protocol of moexipril monotherapy or combination therapy (with hydrochlorothiazide). Blood pressure, pulse rate, weight, adverse effects and laboratory studies were assessed following moexipril at 7.5 or 15 mg once daily or 7.5 or 15 mg daily in combination with 25 mg of hydrochlorothiazide if the seated DBP remained > or = 90 mm Hg on moexipril monotherapy. The primary measure of efficacy was a change from baseline in seated DBP. Secondary outcome measures included changes in seated DBP, pulse rate, laboratory parameters and adverse side-effects. Following 1 year of therapy in 135 patients, the BP fell 16/14 mm Hg among patients receiving moexipril monotherapy and 27/17 mm Hg for those receiving combined therapy compared with baseline (P < 0.001 for both). After 2 years of treatment, reductions were similar in 120 patients. Nineteen patients (11%) were prematurely withdrawn from the study because of inadequate therapeutic response and 28 (16%) because of adverse experiences. There were no significant changes in pulse rate or postural reductions in BP on either moexipril monotherapy or combination treatment. Three adverse side-effects occurred at a frequency exceeding 2% that were possibly or probably attributable to moexipril or combination therapy: hypotension (2%), dizziness (6%) and increased cough (12%). There were no clinically relevant mean group changes from baseline laboratory values in the treatment groups. In conclusion, these long-term data demonstrate that moexipril, either alone or in combination with hydrochlorothiazide, has long-term anti-hypertensive efficacy and is generally well tolerated in elderly patients with hypertension.

Aged↗
PubMed1994

Accelerated hypertension with encephalopathy due to an isolated dissection of a renal artery branch vessel.

Typical causes of renovascular hypertension include intramural atherosclerotic lesions of the main renal arteries or their branches and fibromuscular dysplasia of the renal arterial wall with luminal narrowing. We report a patient with new-onset, accelerated hypertension (blood pressure 220/140 mm Hg, status epilepticus, retinal hemorrhages) secondary to a dissection of the anterior division of the right renal artery that was accompanied by hyperreninemia, hyperaldosteronism, and hypokalemia. At presentation in the untreated state, unstimulated plasma renin activity and the serum aldosterone level were markedly elevated. Following right nephrectomy, blood pressure levels normalized without antihypertensive therapy, and plasma renin activity, serum aldosterone and potassium levels normalized. Histologic study of the right renal artery showed an isolated dissection of the anterior branch of the vessel between the muscularis and adventitia that created marked reduction in luminal diameter and renal ischemia. There was no evidence of any other vascular abnormalities, atherosclerosis, or fibromuscular dysplasia. These findings demonstrate that an isolated dissection of a branch of the renal artery may induce profound hyperreninemia and represents a rare, reversible etiology for accelerated hypertension associated with acute encephalopathy.

Adult↗
PubMed1994

Multicenter assessment of the QuietTrak ambulatory blood pressure recorder according to the 1992 AAMI guidelines.

To clinically evaluate the QuietTrak ambulatory blood pressure (BP) recorder (Tycos-Welch-Allyn, Arden, NC), we assessed the device according to the performance criteria set out by the 1992 Association for the Advancement of Medical Instrumentation (AAMI) guidelines. The QuietTrak is a portable, noninvasive recorder that uses an auscultatory measuring system. As recommended in the 1992 AAMI guidelines, a large, heterogeneous population was recruited for the study using three clinic sites to assess accuracy and clinical performance. In addition, observer agreement and the effects of age, arm circumference, heart rate, posture, and blood pressure level on the observer-device differences were analyzed. There were 1098 simultaneous, same arm BP measurements performed in 122 subjects by the QuietTrak recorder versus two skilled clinicians per site using a teaching stethoscope and 24-h blood pressure recordings performed in 46 subjects to assess reliability of the monitor. The differences in observers for all sites were 0.7/-0.5 +/- 3.8/3.5 mm Hg with 89% of the BPs within 5 mm Hg. The mean difference between observer average and the device (all positions) was 0.3/-1.5 +/- 5.0/7.5 mm Hg. The agreement between the QuietTrak and mercury column determinations was within 10 mm Hg for 92 to 94% of systolic readings and 91 to 93% of diastolic readings, depending on the posture. The limits of agreement (2 standard deviations about the mean difference) between observers and the device for systolic BP tended to be lower for the sitting position (-11 to 10 mm Hg) compared to supine (-14 to 13 mm Hg) and standing (-14 to 14 mm Hg) positions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Contribution of ambulatory blood pressure monitoring to the design and analysis of antihypertensive therapy trials.

Ambulatory blood pressure monitoring is an accepted method of blood pressure measurement in hypertension trials. It is more reproducible than office blood pressure, does not show a placebo effect, and excludes white-coat hypertensive people, therefore offering significant advantages over office-based measurement. Investigators are aware of these advantages, and the use of ambulatory monitoring in hypertension trials is increasing.

Antihypertensive Agents↗
PubMed1994

The relationships between casual and ambulatory blood pressure measurements and central hemodynamics in essential human hypertension.

OBJECTIVE: To determine the association between ambulatory blood pressure (ABP) and central hemodynamics in hypertensive patients and between the area under the 24-h blood pressure curve and the hemodynamic indexes. PATIENT POPULATION: Forty untreated essential hypertensive patients (28 previously untreated, 12 withdrawn from therapy for > 12 weeks). METHODS: Patients underwent casual and 24-h ABP monitoring and invasive measurements of central hemodynamics. Central measures of ABP included 24-h mean, awake, and sleep values guided by activity journals. The ABP data were modeled by Fourier series and the ability of the smoothed and unsmoothed data to predict hemodynamics was compared. Individual blood pressure curves were analyzed by calculating the area under the curve using different threshold awake and sleep values to test the correlations between this form of blood pressure load and hemodynamics. RESULTS: Hemodynamic measures were not predicted by casual blood pressure but were related to ABP. Total peripheral resistance was strongly predicted by the area under the diastolic blood pressure (DBP) curve using an awake threshold of 90 mmHg and a sleep threshold of 80 mmHg (r = 0.56, P < 0.001). Data smoothing using Fourier transformation did not alter any correlations between ABP and hemodynamics. Exercise stroke index, an indicator of cardiac function impaired in early hypertensive heart disease, was also best predicted by area under the DBP curve using the same thresholds as above (r = -0.56, P < 0.001). CONCLUSIONS: These data imply that integrated areas under the ABP curve are related to hemodynamic hypertensive indexes and could be used to assess the extent of hypertensive burden in clinical trials.

Adult↗
PubMed1994

Long-term efficacy and safety of moexipril in the treatment of hypertension.

The purpose of this study was to assess the long-term efficacy and safety of moexipril, a new angiotensin-converting enzyme inhibitor, alone or in combination with hydrochlorothiazide in patients with hypertension. The patient population consisted of 281 hypertensive men and women, 30-84 years old, with seated diastolic BP between 95 and 114 mmHg. The study was a two year multicenter (22 centers), open-label protocol of moexipril monotherapy or combination therapy (with hydrochlorothiazide). Blood pressure, pulse rate, weight, adverse side-effects and laboratory studies were assessed following moexipril dosing at 7.5, 15 or 30 mg once daily or 15-30 mg daily in combination with 12.5 mg hydrochlorothiazide if the DBP was > or = 90 mmHg. The primary measure of efficacy was change from baseline in seated DBP. Secondary outcome measures included changes in seated SBP, heart rate, laboratory parameters and subjective complaints. Following one year of therapy in 183 patients, the BP fell 13/14 mmHg among patients receiving moexipril monotherapy and 18/15 mmHg those receiving combined therapy compared with baseline (P < 0.001 for both). After two years of treatment, reductions were similar in 161 patients. Forty-four (16%) patients were prematurely withdrawn from the study because of inadequate therapeutic response and 34 (12%) secondary to adverse experiences. There were no changes in pulse rate or postural BP reductions. Four adverse side-effects occurred at a frequency exceeding 2% that were possibly or probably attributable to moexipril: fatigue (3%), headache (2%), dizziness (3%) and increased cough (5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Long-term reproducibility of ambulatory blood pressure.

OBJECTIVE: To compare the reproducibility of ambulatory and office blood pressure readings in established hypertensive subjects when studies are repeated at extended time intervals. SUBJECTS: Twenty-five hypertensive patients (office diastolic blood pressure > or = 90 mmHg) who were off antihypertensive therapy for at least 4 weeks and had repeat office and ambulatory blood pressures at least 3 months apart under similar study conditions. METHODS: On the same day, patients underwent office blood pressure readings measured by mercury column sphygmomanometry and then by ambulatory blood pressure monitoring. Ambulatory blood pressure monitoring was done for 24 h, and awake and sleep periods were divided according to a diary kept by each patient. A second study was performed in an identical manner at a mean +/- SD interval of 23 +/- 24 months (range 3-80, median 15). The agreement between studies was assessed by correlation coefficients, coefficients of variation and standard deviation of the differences (SDD). RESULTS: There were no significant differences in office, 24-h, awake and sleep mean blood pressures between the two studies. Mean 24-h systolic and diastolic blood pressures were 16 and 14 mmHg lower, respectively, than office blood pressure values. Correlation coefficients were significantly higher for 24-h ambulatory blood pressure than office blood pressure, whereas the SDD between visits was significantly lower for 24-h ambulatory blood pressure than office blood pressure. CONCLUSIONS: These data demonstrate that long-term reproducibility of ambulatory blood pressure is superior to that for office measurement. One implication of this finding is that, in long-term clinical pharmacology trials utilizing ambulatory blood pressure, fewer subjects would be required than for studies that used office blood pressure end-points.

Adult↗
PubMed1994

Comparison of cellular and extracellular proteins expressed by various isolates of Mycobacterium paratuberculosis and other mycobacterial species.

Protein expression profiles of 10 isolates of Mycobacterium paratuberculosis, M avium 18 (formerly M paratuberculosis 18), and 1 isolate each of M avium serotype 2, M avium serotype 8, and M bovis BCG were examined. Protein expression profiles of M paratuberculosis and M avium were similar. However, two-dimensional gel analysis of [35S]methionine-labeled cellular proteins resolved 4 proteins, with molecular mass of 28,000, 32,000, 32,000, and 42,000 daltons, which were expressed in greater amounts in M paratuberculosis than in M avium. Two proteins, with molecular mass of 43,000 and 60,000 daltons, were identified, which were expressed in greater amounts in M avium than in M paratuberculosis. Immuno (western)-blot analysis, using antiserum from 2 cows clinically infected with M paratuberculosis as the primary antibodies, suggested that the 42,000-dalton protein may be specific for M paratuberculosis. Comparison of protein expression profiles may be useful as a tool for differentiating isolates of M paratuberculosis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [35S]methionine-labeled extracellular proteins revealed variability among the isolates. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [35S]methionine-labeled cellular proteins divided the M paratuberculosis isolates into 2 groups on the basis of a difference in the amount of expression of a 28,000-dalton protein. This information may be useful in epidemiologic studies.

Animals↗
PubMed1993

Management of hypertension after ambulatory blood pressure monitoring.

OBJECTIVE: To study the test-ordering behavior of practicing physicians regarding ambulatory monitoring of blood pressure and to assess changes in patient management after this study. DESIGN: Cross-sectional assessment of physicians' practice habits regarding the ordering of ambulatory blood pressure monitoring and a longitudinal study of patient management after monitoring. SETTING: Physicians' offices in central Connecticut. PARTICIPANTS: Two hundred thirty-seven consecutive patients referred by 65 community- and hospital-based physicians. MEASUREMENTS: Indications for ambulatory blood pressure monitoring, changes in diagnosis and therapy, and office blood pressures before and after the ambulatory blood pressure study. RESULTS: The main indications for ordering the test included borderline hypertension (27% of studies ordered), assessment of blood pressure control during drug therapy (25%), evaluation for "white coat" or "office" hypertension (22%), and drug-resistant hypertension (16%). After the ambulatory blood pressure study, only 13% of the patients had further testing (for example, echocardiography); the diagnosis was changed in 41% of the patients, and antihypertensive therapy was changed in 46%. In 122 patients for whom data were complete, office blood pressure measured by the referring physician decreased from 161/96 +/- 22/12 mm Hg before the ambulatory blood pressure study to 151/86 +/- 27/12 mm Hg 3 months after the study (P = 0.004 for systolic blood pressure and P < 0.001 for diastolic blood pressure). One to 2 years after the study, office blood pressure was 149/86 +/- 24/12 mm Hg (P > 0.2 compared with 3 months after the study). Seventy-two percent of the patients had a lower office blood pressure within 3 months of the ambulatory blood pressure study. CONCLUSIONS: Practicing physicians use ambulatory blood pressure recordings for appropriate indications, and data from the monitoring studies affected the management of patients with hypertension.

Ambulatory Care↗
PubMed1993

Unilateral renal artery stenosis seen initially as severe and symptomatic hypokalemia. Pathophysiologic assessment and effects of surgical revascularization.

Hypokalemia is an uncommon presentation of renovascular hypertension. Although renal artery stenosis has been associated with hypokalemia secondary to hyperreninemic hyperaldosteronism, few reports have actually evaluated the pathophysiologic changes in such a patient with renovascular hypertension. We studied a patient before and after surgical revascularization who presented with severe hypertension and marked, symptomatic hypokalemia. Before surgery, the patient had excessive urinary potassium secretion, markedly increased secretion of renin after captopril stimulation, and mild secondary hyperaldosteronism. Postoperatively, the patient's blood pressure decreased moderately and the serum and urinary potassium values normalized. After revascularization, plasma renin activity both before and after captopril stimulation and serum aldosterone levels decreased markedly. These findings demonstrate that renovascular hypertension may rarely present with symptomatic hypokalemia secondary to excessive aldosterone secretion. Improvement in the renal ischemic state is accompanied by rapid correction of the metabolic disturbances associated with hyperreninemic hyperaldosteronism.

Aldosterone↗
PubMed1993

Fenoldopam, but not nitroprusside, improves renal function in severely hypertensive patients with impaired renal function.

PURPOSE: Patients with hypertensive crises often experience reduced renal function that may worsen as the elevated blood pressure is treated. Fenoldopam, a novel, peripherally acting dopamine-1 agonist, lowers blood pressure through arteriolar vasodilation, with particularly prominent effects on the renal vascular bed. This study was conducted to examine the effects of fenoldopam on blood pressure and renal function compared to those of sodium nitroprusside in severely hypertensive patients with impaired renal function. PATIENTS AND METHODS: Renal function and systemic hemodynamics were studied in 19 severely hypertensive patients (diastolic blood pressure greater than or equal to 120 mm Hg) with impaired renal function (creatinine clearance less than or equal to 70 mL/min) enrolled in clinical trials of fenoldopam and sodium nitroprusside. For comparison, an additional 22 severely hypertensive patients with nonimpaired renal function were studied under the same conditions. Blood pressure and heart rate were measured at baseline before treatment and periodically during treatment. Renal function was determined before and during drug infusion by collection of timed urine specimens and blood samples. Creatinine clearance, urine flow rate, and sodium and potassium excretions were measured and compared. RESULTS: In patients with impaired renal function, blood pressure (mean +/- SEM) was reduced successfully in both groups (fenoldopam: 214 +/- 8/139 +/- 6 mm Hg to 176 +/- 8/107 +/- 3 mm Hg, p < 0.001 for systolic and diastolic comparisons; nitroprusside: 226 +/- 4/145 +/- 5 mm Hg to 171 +/- 6/108 +/- 2 mm Hg, p < 0.001 for systolic and diastolic comparisons). Results of renal function studies showed significant increases in creatinine clearance (from 39 +/- 7 mL/min to 75 +/- 16 mL/min, p < 0.05), urine flow (from 119 +/- 37 mL/h to 275 +/- 84 mL/h, p < 0.01), and sodium excretion (from 75 +/- 22 microEq/min to 227 +/- 60 microEq/min, p < 0.01) in patients with impaired renal function treated with fenoldopam. No significant changes were seen in patients treated with nitroprusside. In patients with nonimpaired renal function, blood pressure was reduced by both agents, but only patients who received fenoldopam experienced significant increases in creatinine clearance, urine flow rate, and sodium excretion. CONCLUSION: Fenoldopam, but not nitroprusside, improved renal function in severely hypertensive patients at all levels of baseline renal function while lowering blood pressure. Because of these effects, fenoldopam may be particularly useful in treating severely hypertensive patients with impaired renal function.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1993

Ambulatory blood pressure monitoring.

During the past decade, ambulatory blood pressure monitoring has risen rapidly as a diagnostic technique used in clinical research trials and, more recently, in clinical practice. Blood pressure monitors have become smaller, technologically improved, and quiet during recordings--all features that have increased patient compliance. During the past year, research has focused on establishing population norms for ambulatory blood pressure levels, improving methods of validating devices, enhancing our ability to reduce the ambulatory blood pressure data and provide clinically meaningful methods of statistical analysis, and evaluating the role of blood pressure monitoring in the management of hypertension in ambulatory care.

Blood Pressure Monitoring, Ambulatory↗
PubMed1993

National standard for measurement of resting and ambulatory blood pressures with automated sphygmomanometers.

The Association for the Advancement of Medical Instrumentation develops voluntary standards for medical devices so that manufacturers might provide information on their product and basic safety and performance criteria that should be considered in qualifying the instrument for clinical use. American national standards are generated through a consensus process by committees consisting of experts in research, development, and design from user, industry, and government communities. Draft standards are made available for public review and may become American national standards after review by the American National Standards Institute. The first American national standard for electronic and automated sphygmomanometers was published in monograph form in 1987. The objective of the revised 1992 standard for electronic and automated sphygmomanometers is to provide updated labeling, safety, and performance requirements that help ensure that consumers and health care professionals are supplied with safe, accurate devices for the indirect measurement of blood pressure, including ambulatory blood pressure recorders. This standard permits validation of the automatic or electronic device by comparison with either direct, intra-arterial blood pressure measurements or the noninvasive cuff/stethoscope technique, based on Korotkoff sounds identified by individuals trained in auscultation. This summary report of the 1992 American national standard for automatic sphygmomanometers provides recommendations for the methods of comparison, statistical analysis of the data, presentation of the results, and criteria for acceptability. Users, researchers, and instrument designers should refer to the American national standard monograph for detailed requirements.

Autoanalysis↗