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Biomedical subjects

M A Weber

Publications and source records attributed to M A Weber.

At least 163 records · Page 9Linked to original sources
PubMed1988

Evaluating the diagnosis and prognosis of hypertension by automated blood pressure monitoring: outline of a symposium.

The technique of automated whole-day blood pressure monitoring by noninvasive, lightweight portable devices has recently become available for clinical use. This article, together with the six that follow it, comprise the proceedings of a symposium on the diagnostic and prognostic use of this new approach. There is a growing belief that standard clinical methods may overdiagnose hypertension (the phenomenon of "white coat" or "office" hypertension), subjecting some patients to unnecessary long-term treatment. The automated blood pressure monitoring procedure may be especially helpful in evaluating patients whose office-diagnosed hypertension is not associated with confirmatory clinical findings or history. Data derived from whole-day blood pressure measurements appear to be more reproducible than conventional blood pressure values and correlate more closely with evidence for cardiovascular changes. This symposium has addressed some of the issues associated with the monitoring techniques, including the accuracy of values obtained with noninvasive equipment, interpretation of the data, and costs of the procedure. The evidence and arguments presented by these papers suggest that automated blood pressure monitoring is becoming a justified and desirable procedure in selected patients with a preliminary clinical diagnosis of mild to moderate hypertension.

Blood Pressure↗
PubMed1988

Validation of portable noninvasive blood pressure monitoring devices: comparisons with intra-arterial and sphygmomanometer measurements.

We have evaluated the accuracy of measurements provided by different types of portable automatic blood pressure monitoring devices by comparing them with intra-arterial and mercury sphygmomanometer measurements in 25 hospitalized patients. Systolic blood pressure values with portable devices that use auscultatory or oscillometric methods of measurement correlated significantly with intra-arterial values (r = 0.74 and 0.89; p less than 0.001 for both); similarly, diastolic values correlated significantly (r = 0.86 and 0.81; p less than 0.001 for both). Compared with intra-arterial measurements, there was a slight tendency for the portable devices to underestimate systolic blood pressure and overestimate diastolic blood pressure. Correlations between auscultatory or oscillometric measurements and sphygmomanometer measurements in these patients were also significant; moreover, the absolute blood pressure values obtained with the portable devices were almost identical to those with the sphymomanometer. In a further group of 12 volunteers, auscultatory and oscillometric values correlated very closely with simultaneously measured sphygmomanometer values for both systolic (r = 0.99 and 0.98) and diastolic (r = 0.96 and 0.94) blood pressures. An auscultatory device that uses continuous ECG R wave gating for Korotkoff sounds was also found to be highly accurate. Thus we have found that automated portable devices that use either auscultatory or oscillometric methods of measurement provide reliable blood pressure values.

Auscultation↗
PubMed1988

Intravenous recombinant tissue plasminogen activator (rt-PA) and urokinase in acute myocardial infarction: results of the German Activator Urokinase Study (GAUS).

The effects of recombinant tissue plasminogen activator (rt-PA) and urokinase on patency and early reocclusion of infarct-related coronary arteries were investigated in a single blind, randomized multicenter trial in 246 patients with acute myocardial infarction of less than 6 h duration. Both 70 mg of single chain rt-PA with an initial bolus of 10 mg and 3 million units of urokinase with an initial bolus of 1.5 million units were given intravenously over 90 min. The first angiographic study at the end of the infusion revealed a patent infarct-related artery (Thrombolysis in Myocardial Infarction trial [TIMI] grade 2 or 3) in 69.4% of 121 patients given rt-PA versus 65.8% of 117 patients given urokinase (p = NS). Among patients treated within 3 h from symptom onset a patent infarct-related artery was found in 63.9% of 72 patients given rt-PA versus 70% of 70 patients given urokinase (p = NS). There were five cardiac deaths in each group and one fatal intracranial hemorrhage in the rt-PA group. The in-hospital reinfarction rate was 8.9% versus 13.2% for patients treated with rt-PA and urokinase, respectively. There was no difference in left ventricular function at baseline and follow-up catheterization studies. Both drugs were well tolerated and there was no significant difference in cardiovascular or bleeding complications between the two groups. It is concluded that rt-PA and urokinase in the dosages used provide similar efficacy and safety in the treatment of acute myocardial infarction. Reocclusion during the first 24 h may be less frequent after urokinase treatment.

Adult↗
PubMed1988

Correlates of cardiac structure and function in normotensive adolescents.

To evaluate body weight as a determinant of cardiac structure and function in adolescents, 47 normotensive 13-year-old subjects were studied with M-mode echo duplex Doppler echocardiography (DE). They were separated by body weight into standard (greater than 55 kg) and lighter (less than 55 kg) groups. No subject had a blood pressure greater than 140/90. The differences between the groups in systolic (SBP) and diastolic (DBP) blood pressures, LV mass, left atrial size (LA), and peak aortic flow velocity (PAoV) were measured. (Formula: see text). Body weight strongly correlated with SBP in the entire study group (r = 0.66, P less than 0.001) but slightly less strongly with DBP (r = 0.48, P less than 0.001). Left ventricular filling indices such as peak early diastolic flow velocity, early diastolic filling integral, peak atrial flow velocity, and atrial filling integral were not significantly different between the groups. No significant differences in blood pressure, LV mass, LA size, or peak aortic flow velocity could be demonstrated when the subjects were subdivided on the basis of gender or presence or absence of family history of hypertension. Body weight appeared to be not only a strong predictor of blood pressure but also of cardiac structural and functional characteristics in adolescents.

Adolescent↗
PubMed1988

Diastolic blood pressure and left ventricular filling.

Many factors appear to influence diastolic left ventricular (LV) filling, including age, hypertension, and myocardial and coronary disease. Doppler-echocardiography was used to asses the influences of blood pressure (BP) on LV filling in 43 normotensive volunteers aged 12 +/- 0.98 years with heart rates less than or equal to 90 beats/min. Doppler peak diastolic transmitral flow velocities, diastolic flow integrals, and early diastolic deceleration were measured. An interesting difference was noted between the influence of systolic and diastolic BP. Systolic BP was related to LV mass (r = 0.43; P less than 0.005), but was unrelated to any of the Doppler filling indices. Diastolic BP was unrelated to LV mass, but was inversely related to peak early diastolic flow velocity (r = -0.37; P less than 0.05), early diastolic flow velocity integral (r = -0.34; P less than 0.05). The ratio of late-to-early filling (A/E) was directly related to diastolic BP (r = 0.42; P less than 0.005). The relationship between A/E and diastolic BP was strong in subjects (n = 21) with bimodal P waves in electrocardiogram (ECG) lead V1 (r = 0.61; P less than 0.005), but absent in those (n = 15) with unimodal P waves (r = 0.18; P = NS). Thus, the pattern of LV filling is related to the level of diastolic BP in normal adolescents, especially in those with bimodal P waves on ECG. These diastolic BP related changes are independent of heart rate and LV hypertrophy and may represent very early pre-hypertensive alterations in LV diastolic function.

Adolescent↗
PubMed1988

Prolonged calcium channel blocker therapy of hypertension.

The dihydropyridine calcium channel blocker nitrendipine was studied in 329 hypertensive patients at 12 separate centers for periods of 1 year or more. Patients with untreated supine diastolic blood pressures greater than 90 mm Hg were given nitrendipine 5 mg twice daily for 1 week; if the goal blood pressure was not achieved (supine diastolic blood pressure less than 90 mm Hg with a fall of at least 10 mm Hg), the dose was doubled, and if necessary it was doubled again after an additional week. By the end of titration, the goal blood pressure had been achieved in 138 patients (44%). During the subsequent 11 months of study, 155 patients continued to take nitrendipine alone; their posttitration supine diastolic blood pressure was 85 +/- 7 mm Hg, and at the end of the 1 year study it was 84 +/- 6 mm Hg. There were no significant changes in body weight or in heart rate. At their discretion, investigators could add other antihypertensive agents in patients not responding adequately to nitrendipine alone. In 41 patients with a supine diastolic blood pressure of 95 +/- 9 mm Hg after initial titration, propranolol was added to the nitrendipine and decreased the supine diastolic blood pressure to 88 +/- 8 mm Hg by the end of the study; and in another 76 patients with a posttitration supine diastolic blood pressure of 92 +/- 7 mm Hg, the addition of hydrochlorothiazide decreased the supine diastolic blood pressure to 86 +/- 7 mm Hg by the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Atrial natriuretic factor-induced vasodepression occurs through central nervous system.

To characterize the blood pressure and heart rate effects of atrial natriuretic peptide (ANP) in the brain, we administered 20 micrograms/kg of atriopeptin III in 5 microliters of 0.9 normal saline into the fourth ventricle of awake, freely moving, spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. ANP produced a 13 +/- 1 mmHg decrease in mean arterial blood pressure (MAP) in the SHR (P less than 0.001 vs. base line or saline control, n = 10) and a 9 +/- 2 mmHg decrease in the WKY (P less than 0.02). Heart rate did not change significantly in response to ANP. To determine whether an interaction with the adrenergic nervous system played a role in the effects of ANP, we administered 100 ng yohimbine HCL, an alpha 2-antagonist, by intracerebroventricular injection, 45 min before ANP and completely prevented the ANP-induced decrease in MAP. In contrast, 100 ng intracerebroventricular prazosin, an alpha 1-adrenergic antagonist, had no significant influence on the MAP effect induced by ANP. A third group of SHR was pretreated with intracerebroventricular 6-OH dopamine to deplete central catecholamines or with saline. The rats pretreated with 6-OH dopamine (n = 6) had no significant response to ANP, which was administered 9 days later. This was significantly different from the saline-pretreated control group (n = 6), which responded with a 19 +/- 3 mmHg decrease in MAP (P less than 0.025). These studies indicate that the administration of ANP into the fourth ventricle of the brain decreases the MAP of rats through an interaction with the central alpha 2-adrenergic nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Angiotensin II amplification of alpha-adrenergic vasoconstriction: role of receptor reserve.

Angiotensin II (Ang II) is known to enhance the vasoconstrictor response to norepinephrine (NE). In the present study, this interaction was investigated using isolated rabbit femoral artery rings mounted in tissue baths for the measurement of isometric contraction. Exposure to 3 x 10(-10) M Ang II caused a contraction that was less than 5% of the maximal response to NE. In the presence of Ang II, the NE dose-response curve shifted to the left twofold and the maximal response was not changed. The calcium channel antagonist nifedipine, 1 x 10(-7) M, caused a modest inhibition of the response to NE in either the presence or absence of Ang II. In contrast, nifedipine abolished the leftward shift of the NE dose-response curve caused by Ang II. Femoral arteries were pretreated with benextramine to cause partial alpha-adrenoceptor inactivation. The maximal contractile response to NE in these tissues was between 20% and 40% of that in control vessels, indicating that alpha-adrenoceptor reserve had been eliminated. In benextramine-pretreated vessels, the presence of 3 x 10(-10) M Ang II caused a modest leftward shift of the NE dose-response curve but increased the maximal responses to all NE concentrations by 200% to 800%. Nifedipine caused a modest inhibition of the response to NE in the absence of Ang II. In contrast, the enhanced response to NE in the presence of Ang II was nearly abolished. These results support our conclusions that 1) Ang II enhances the vasoconstrictor response to alpha-adrenergic stimulation, 2) the magnitude of enhancement is greater under conditions of reduced alpha-receptor reserve, and 3) calcium channel activation plays a major role in the amplified response.

Angiotensin II↗
PubMed1988

[Intravenous infusion of recombinant tissue-type plasminogen activator (rt-PA) and urokinase in acute myocardial infarct: intermediate results of the G.A.U.S. study (German Activator Urokinase Study)].

The effects of recombinant tissue plasminogen activator (rt-PA) and urokinase on patency and early reocclusion of infarct-related coronary arteries were investigated in a single blind, randomised multicenter trial in up to now 125 patients with acute myocardial infarction of less than six hours duration. Both, 70 mg of single-chain rt-PA with an initial bolus of 10 mg, and 3 million U of urokinase with an initial bolus of 1,5 million U were given intravenously over 90 minutes. The first angiogram at the end of the infusion revealed a patent infarct-related artery (TIMI grade 2 or 3) in 68% of 62 patients with rt-PA vs. 63% of 63 patients with urokinase (n.s.). Twenty-four hours later patent infarct-related arteries occurred in the same frequency in the rt-PA group and in the urokinase group (71.5% vs. 74.6%, n.s.), although additional recanalisation procedures in sequence with the first angiography were performed more frequent in the rt-PA group. There were two cardiac deaths in either group. In-hospital reinfarction rate was 9.7% vs. 17.5% for patients treated with rt-PA and urokinase, respectively. Both drugs were well tolerated, no significant difference of cardiovascular or bleeding complications could be observed between the two groups. It is concluded that rt-PA and urokinase in the dosages used provide similar efficiency and safety in the treatment of acute myocardial infarction.

Adult↗
PubMed1988

Ambulatory blood pressure measurements: practical considerations, methodology, feasibility, and implications in the management of hypertension.

Automated ambulatory blood pressure monitoring is a safe new technique that allows a more exact assessment of the diagnosis and treatment of hypertension than has been possible previously. It should be of great value in helping avoid unnecessary pharmacologic treatment of certain patients and in tailoring therapy to individual needs. Further research is needed to determine the role of ambulatory monitoring in the detection of hypertension, in the assessment of cardiovascular symptoms, and in the definition and treatment of labile hypertension. Because this technique has been developed subsequent to the research that underlies our current understanding of the effect of hypertension and the treatment of hypertension on cardiovascular disease, further prospective studies are needed to confirm its value in predicting hypertensive complications. A growing body of evidence indicates that ambulatory blood pressure may be a much more powerful predictor of cardiovascular risk than conventional blood pressure measurements.

Ambulatory Care↗
PubMed1988

Feeding patterns of urban black infants.

Feeding patterns of 116 urban black infants were studied from 3 weeks to 6 months of age. Dietary data were collected using a diet history and a food frequency checklist completed by trained interviewers at each well child clinic visit at 3 weeks and at 2, 4, and 6 months of age. At 3 weeks, 20% of the infants were solely breast fed, 58% were formula fed, and 22% were partially breast fed. Twenty percent of 3-week-old infants were receiving baby foods. This increased to 48% at 2 months, and to 72% at 4 months. By 6 months of age, 98% of infants received baby foods. Nursing mothers tended to introduce baby foods later than formula-feeding mothers. This is consistent with other studies. Commercially prepared baby foods were used much more commonly than were foods prepared at home. Infant cereal was most often introduced first, followed by strained juices, strained fruits, strained vegetables, combination dinners, desserts, and plain meats, in that order. Table foods contributed very little to caloric intakes of infants less than 4 months of age. Liberal amounts of water and sugar water were given to infants in this cultural group.

Adult↗
PubMed1987

Studies of the penetration of the blood brain barrier by atrial natriuretic factor.

The atrial natriuretic factors (ANF) have been detected in various areas of the brain. To determine whether circulating blood borne ANF could contribute to the ANF content in the central nervous systems we examined the ability of ANF-99-126 or ANF-102-126 to penetrate the blood brain barrier. Carotid artery injections of [3H] inulin with [125I] ANF in anesthetized rabbits resulted in a comparably minimal brain uptake index (BUI) for each labeled substance as measured in cerebral cortex extracts. Injection of [3H] HOH and [125I] ANF resulted in a mean BUI in cortex of 4.9 +/- .6 (SEM)% for ANF relative to triated water; this low uptake was not significantly saturable. The BUI ratio for ANF/HOH in olfactory bulb was somewhat higher though still low, at 7.0 +/- 9%, possibly reflecting the high density of ANF receptors in this structure. Infusion of [125I] ANF into the carotid artery of anesthetized rabbits resulted in little radioactivity being detected in the cerebrospinal fluid. Infusion of unlabeled ANF, which raised plasma levels as high as 26.3 ng/ml, resulted in little change in CSF levels. Our results demonstrate that the uptake of ANF into the brain is minimal and supports the idea that local synthesis of ANF predominantly accounts for the brain pool of this peptide.

Animals↗
PubMed1987

Effect of antihypertensive therapy on the circadian blood pressure pattern.

This study employed 24-hour automated ambulatory blood pressure monitoring to evaluate whole-day patterns of blood pressure in age-matched groups of normotensive volunteers, untreated hypertensive patients, and hypertensive patients treated with prazosin. As would be expected, overall systolic and diastolic blood pressures were found to be lowest in the normotensive subjects and highest in the untreated hypertensive patients. The systolic and diastolic blood pressure values for patients receiving prazosin twice daily were significantly lower than in the untreated patients; they were slightly, but not significantly, higher than the values recorded for the normotensive volunteers. The data from 24-hour monitoring revealed no between-group differences in the actual circadian rhythm of the blood pressure. This finding established that the blood pressure pattern for hypertensive patients treated with prazosin was parallel to that for normal individuals. Thus, prazosin administered twice daily reduces blood pressure throughout a full 24-hour period in a fashion that maintains the normal circadian pattern of the blood pressure.

Blood Pressure↗
PubMed1987

Blood pressure monitoring for assessing the duration of action of antihypertensive treatment.

The duration of antihypertensive action of the alpha-adrenergic blocking agent, prazosin, was studied in 12 hypertensive patients in whom twice-daily doses of this agent were found to be effective and well tolerated during a preliminary titration period. The patients then entered a cross-over phase of study. On a randomized basis, they were given prazosin either twice daily for eight weeks followed by an eight-week period in which they received the same total dose once daily (each morning), or they were given the treatment for a once-daily period followed by a twice-daily period. Using the conventional sphygmomanometer, there were no significant differences in blood pressures for the patients as a whole between the measurements during once-daily dosage (measured approximately 24 hours after the last administration of drug) and those during twice-daily dosage (measured approximately 12 hours after the last administration); but for both methods of administration, blood pressures were significantly lower than pre-treatment values. Automated whole-day ambulatory blood pressure monitoring showed a tendency for blood pressures to be lower with once-daily than with twice-daily treatment during the first 12 hours after the morning doses were given, but there was a reversal of this pattern during the early morning hours preceding the next dose. However, for at least half of the patients these differences were only minimal. Thus, prazosin may be effective in some patients as once-daily treatment, especially after several weeks of therapy. Moreover, automated whole-day blood pressure monitoring appears to be a valuable technique for guiding dosage requirements for patients on an individual basis.

Adult↗
PubMed1987

The adrenergic inhibitors.

Although most of the centrally and peripherally-acting adrenergic inhibitors have been available for several years, they continue to contribute importantly to antihypertensive therapy. There are remarkably few contraindications to their use. They are useful in hypertension of all grades of severity, and are also valuable in complicated forms of hypertension, such as those associated with renal insufficiency, diabetes mellitus, and chronic obstructive lung disease. They can produce some fairly predictable side effects in patients, but generally do not cause significant metabolic changes. These drugs also seem to be tolerated well by physically active patients. They appear to have desirable effects on cardiac structure. In general, the adrenergic inhibitors cause regression of a left ventricular hypertrophy, which may well be a valuable property, especially in older hypertensive patients.

Adrenergic alpha-Antagonists↗