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Biomedical subjects

G Mancia

Publications and source records attributed to G Mancia.

At least 343 records · Page 19Linked to original sources
PubMed1992

Coronary response to diving in subjects with mild and severe left coronary artery disease.

The cold pressor test (CPT) is commonly used to determine the vasospastic origin of angina and to investigate the factors modulating coronary vasomotor tone. However, coronary vasoconstriction associated with this manoeuvre is often limited, particularly in patients with mild coronary atherosclerosis. To identify stimuli that can more powerfully constrict the coronary arteries we compared the effects on coronary blood flow (thermodilution) and vascular resistance (mean aortic pressure divided by coronary blood flow) of CPT (2 min) and diving (D, 45 s) in subjects with angiographically documented mild (n = 11) or severe (n = 11) left anterior descending coronary artery stenosis. In subjects with severe coronary artery stenosis the rate-pressure product increased to a similar extent with CPT and D. The latter stimulus, however, caused a more marked fall in coronary blood flow and a much more pronounced increase in coronary resistance as compared to CPT (+44 +/- 3.1% vs +19 +/- 1.6%, P less than 0.01). In the face of a similar increase in rate-pressure product, D caused a significant increase in coronary vascular resistance also in patients with mild coronary artery stenosis (less than or equal to 50%) in which CPT failed to induce any coronary vasoconstriction (+16 +/- 1.8% vs +0.3 +/- 1.3%, P less than 0.01). Thus, diving is a much more powerful coronary vasoconstrictor stimulus than CPT. It can thus replace CPT when an increase in coronary resistance is needed for diagnostic purposes or for investigating abnormalities in coronary vascular regulation.

Cold Temperature↗
PubMed1992

Sympathomoderating influence of benazepril in essential hypertension.

OBJECTIVE: In essential hypertension, captopril attenuates forearm vasoconstriction reflexly induced by deactivation of cardiopulmonary and arterial baroreceptors, thus exerting a sympathomoderating effect. We investigated whether this is a common effect of angiotensin converting enzyme (ACE) inhibitors. METHODS AND DESIGN: Cardiopulmonary and arterial baroreceptors were deactivated by progressively reducing central venous pressure (CVP) through progressively greater lower body negative pressures in eight untreated mild essential hypertensives on a moderately low-sodium diet (50 mmol/l per day). This deactivation was performed after oral administration of the non-sulphidrylic ACE inhibitor benazepril (10 mg) and placebo according to a double-blind randomized crossover experimental design. RESULTS: After placebo, the reduction in CVP increased forearm vascular resistance (FVR; mean arterial pressure: plethysmographic forearm blood flow ratio). After benazepril, baseline blood pressure (beat-to-beat finger pressure) and FVR were significantly reduced whilst plasma angiotensin II was suppressed and PRA increased (both measured by radioimmunoassay). The FVR increases induced by progressive CVP reduction were less than after placebo administration, and the overall difference was statistically significant. Benazepril did not affect the reflex FVR reduction observed by increasing CVP through leg raising, nor the reflex changes in plasma norepinephrine measured by high-performance liquid chromatography accompanying the changes in FVR. CONCLUSIONS: Benazepril attenuates sympathetic vasoconstriction as does captopril. This effect (which is mainly operative during an increased sympathetic drive and exerted through a reduction of adrenoceptor responsiveness) is thus likely to be a class- rather than a compound-related feature.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Persistent blood pressure increase induced by heavy smoking.

OBJECTIVE: To test the hypothesis that heavy smoking is associated with a persistent increase in blood pressure. DESIGN: In 10 normotensive smokers asked to smoke one cigarette every 15 min for 1 h, blood pressure and heart rate were continuously monitored during the smoking period and during the preceding non-smoking hour. In six other normotensive smokers asked to smoke two cigarettes per hour throughout the whole day, blood pressure and heart rate were monitored non-invasively in ambulatory conditions for 8 h (0900-1700 h). Blood pressure monitoring was repeated during a non-smoking day. METHODS: Beat-to-beat blood pressure and heart rate were monitored at rest by means of the Finapres device. Blood pressure signal was sampled at 165 Hz by a computer to calculate hourly data. Ambulatory blood pressure and heart rate were measured once every 10 min. RESULTS: In resting conditions, the first cigarette caused an immediate and marked increase in blood pressure and heart rate, and the peak blood pressure and heart rate achieved were similar for the remaining three cigarettes. In each instance, the hemodynamic effects were so prolonged that throughout the smoking hour, blood pressure and heart rate were persistently higher than during the non-smoking hour. The standard deviations of systolic and diastolic blood pressure and heart rate were also higher during the smoking hour, indicating an increase in blood pressure and heart rate variability. In the six ambulant smokers, daytime blood pressure and heart rate were also persistently higher during smoking than during non-smoking. CONCLUSIONS: Heavy smoking is associated with a persistent rise in blood pressure and also with an increase in blood pressure variability. These effects (which may escape clinic blood pressure measurements performed during non-smoking) may account for some of the smoking-related cardiovascular risk.

Adult↗
PubMed1992

Limited reproducibility of hourly blood pressure values obtained by ambulatory blood pressure monitoring: implications for studies on antihypertensive drugs.

OBJECTIVE: To assess the reproducibility of average hourly blood pressure values obtained by 24-h non-invasive ambulatory monitoring. PATIENTS: Fifteen outpatients with essential hypertension. In all subjects antihypertensive treatment was withdrawn for 4 weeks before and during the 4 weeks of the study. METHODS: The 24-h blood pressure was monitored by a SpaceLabs 5300 device (four readings per hour during the day and three readings per hour during the night) twice, at a 4-week interval. Systolic (SBP) and diastolic blood pressure (DBP) were averaged for each hour and for the whole 24-h period, and hourly and 24-h reproducibility was quantified by the standard deviation of the mean difference (SDD) between the values obtained in the two recordings. RESULTS: The SDD of hourly SBP and DBP was much greater than that of the 24-h values and ranged widely between the hours of recording. The SDD of hourly SBP and DBP were also variably greater than the SDD of the 24-h value in another 14 untreated essential hypertensives in whom 24-h ambulatory blood pressure was monitored intra-arterially twice at a 4-week interval to calculate hourly average blood pressure on thousands rather than on three or four values per hour. CONCLUSION: Reproducibility is less for hourly than for 24-h average blood pressure. This feature (which probably depends on behavioural differences between two recordings) suggests that ambulatory blood pressure measurement partly loses its advantages for reproducibility and reduction in trial size if the results are analysed over hourly periods.

Adolescent↗
PubMed1992

Effect of oral dilevalol on forearm circulation in essential hypertension.

In 7 patients with untreated mild essential hypertension, a single 200-mg dilevalol dose was administered orally. Blood pressure (BP, left brachial artery catheter), heart rate (HR), and left and right forearm blood flows were measured and left and right forearm vascular resistances were calculated before and for approximately 3 h after drug administration. Dilevalol administration was followed by a sustained reduction in BP, little change in HR, and a similar pronounced and sustained increase in left and right forearm blood flows and reduction in left and right forearm vascular resistances. At the end of the observation period, the changes in left forearm circulation were unaffected by left brachial artery infusion of saline but markedly reduced by left brachial artery infusion of propranolol at doses that had no effect on BP, HR, and contralateral forearm vasodilatation. Thus, at an oral dose exerting an antihypertensive effect, dilevalol induces a marked and persistent vasodilation due largely to the beta-adrenoceptor agonism of the drug.

Administration, Oral↗
PubMed1992

Alpha 1-blocking properties of carvedilol during acute and chronic administration.

Carvedilol is a beta-adrenergic-blocking drug with vasodilating properties. This vasodilation has been ascribed to alpha 1-adrenergic blockade, but it has never been shown in the clinical setting. We addressed this issue by studying eight patients with mild essential hypertension who were given prazosin, 2 mg or carvedilol, 25 mg p.o. following a 2-week washout from previous treatment, according to a randomized double-blind, crossover experimental design. Before and 2 h after the administration of either prazosin or carvedilol, the patients were infused i.v. with increasing doses of phenylephrine (0.2-1.2 microgram/kg/min) and isoproterenol (0.01-0.05 microgram/kg/min). The patients were thereafter maintained on carvedilol 25 mg daily for 3 weeks, and the i.v. phenylephrine and isoproterenol infusions were repeated 2 h after the last tablet administration. The results showed that the single dose of carvedilol and prazosin lowered blood pressure (beat-to-beat finger pressure measurement) to a similar extent, but that heart rate was unaffected by prazosin and reduced by carvedilol. The tachycardic response to isoproterenol was abolished by carvedilol and unaffected by prazosin, whereas the pressor response to phenylephrine was reduced by carvedilol and virtually abolished by prazosin. The antihypertensive, beta-blocking and alpha 1-adrenergic-blocking effects of carvedilol were unchanged following prolonged administration of the drug. Thus, at a clinically effective dose, carvedilol not only has beta- but also sizeable alpha 1-blocking effects. These effects are preserved during prolonged administration of the drug. For a comparable antihypertensive action, however, the alpha 1-blocking effect is less pronounced than that of an alpha 1-blocker such as prazosin.

Adrenergic alpha-Antagonists↗
PubMed1992

ACE inhibition attenuates sympathetic coronary vasoconstriction in patients with coronary artery disease.

BACKGROUND: In humans, angiotensin converting enzyme (ACE) inhibition attenuates the vasoconstriction induced by sympathetic stimulation in a number of peripheral districts. Whether this is also the case in the coronary circulation is unknown, however. METHODS AND RESULTS: In nine normotensive patients with angiographically assessed coronary atherosclerosis, we measured the changes in mean arterial pressure (intra-arterial catheter), heart rate, rate-pressure product (RPP), coronary sinus blood flow (CBF, thermodilution method), and coronary vascular resistance (CVR, ratio between mean arterial pressure and CBF) induced by the cold pressor test (CPT, 2 minutes) and diving (30 seconds), i.e., two stimuli eliciting a sympathetic coronary vasoconstriction. The measurements were performed in the control condition and 30 minutes after captopril 25 mg p.o. In the control condition, CPT caused an increase in mean arterial pressure and heart rate. Despite the increase in RPP (+20.7 +/- 3.2%, p less than 0.01), CBF did not change and CVR increased (+12.2 +/- 4.0%, p less than 0.05). diving caused an increase in mean arterial pressure and a reduction in heart rate. RPP increased (+14.3 +/- 3.5%, p less than 0.01), but despite this increase, there was a reduction in CBF and a marked increase in CVR (+37.3 +/- 7.4%, p less than 0.01). Captopril did not modify the blood pressure and heart rate responses to both stimuli except for a slight accentuation of the bradycardia to diving. Despite the unchanged or only slightly reduced RPP response, the increase in CVR was markedly and significantly attenuated (p less than 0.01). CONCLUSIONS: ACE inhibition attenuates sympathetic coronary vasoconstriction in patients with coronary artery disease. This is probably due to removal of the facilitating influence of angiotensin II on sympathetic modulation of coronary vasomotor tone.

Angiotensin II↗
PubMed1992

Cardiac parasympathetic hyperresponsiveness in spontaneously hypertensive rats.

The bradycardic response to baroreceptor stimulation is impaired in human and experimental hypertension. Because this bradycardia mainly depends on the vagus, this may reflect a reduced cardiac parasympathetic responsiveness, which would parallel the reduced cardiac adrenergic responsiveness observed in hypertension. To test this hypothesis, 12-week-old spontaneously hypertensive rats (n = 12) and normotensive Wistar-Kyoto rats (n = 11) were anesthetized with ketamine and underwent bilateral vagotomy. Cardiac parasympathetic responsiveness was assessed from the bradycardia induced by 1) graded electrical stimulation of the right efferent vagus (1-16 Hz) and 2) graded intravenous injections of methacholine (1-8 micrograms.kg-1). The slope of the linear regression between the bradycardiac response and the applied stimulus was taken as the measure of cardiac parasympathetic responsiveness. To identify the onset of possible alterations in cardiac parasympathetic responsiveness in hypertension, the study was extended to younger (8-week-old) spontaneously hypertensive (n = 11) and Wistar-Kyoto (n = 13) rats. With vagal stimulation, cardiac parasympathetic responsiveness was greater in 12-week-old spontaneously hypertensive rats than in 12-week-old Wistar-Kyoto rats (24.8 +/- 5.4 versus 10.1 +/- 1.2 beats per minute per hertz, mean +/- SEM, p less than 0.035). This was also the case with methacholine (18.8 +/- 3.5 versus 13.1 +/- 4.4 beats per minute per microgram per kilogram, p less than 0.045). In contrast, cardiac parasympathetic responsiveness was similar, with both vagal stimulation and methacholine, when tested in the younger spontaneously hypertensive and Wistar-Kyoto groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Evaluation of noninvasive blood pressure monitoring devices Spacelabs 90202 and 90207 versus resting and ambulatory 24-hour intra-arterial blood pressure.

This study evaluated the accuracy of blood pressure values provided by the Spacelabs 90202 and 90207 devices in comparison with intra-arterial recording in 19 subjects at rest and in nine subjects in ambulatory conditions (Oxford method). At rest Spacelabs monitors reflected intra-arterial systolic blood pressure values very closely but overestimated to a considerable extent intra-arterial diastolic blood pressure (Spacelabs-intra-arterial differences, -0.8 +/- 9.2, NS, and 9.1 +/- 8.8 mm Hg, p less than 0.01, for systolic and diastolic blood pressures, respectively). In ambulatory conditions Spacelabs-intra-arterial average differences in 24-hour values were +0.4 +/- 5.1 mm Hg for systolic blood pressure (NS) and +14.0 +/- 2.9 mm Hg for diastolic blood pressure (p less than 0.01) when group data were considered. The performance of both Spacelabs devices was worse when assessed in individual subjects or for each hourly interval. In spite of these differences between noninvasive and intra-arterial absolute blood pressure values, however, Spacelabs 90202 and 90207 monitors were able to faithfully reflect directional hour-to-hour changes in intra-arterial blood pressure (chi 2 = 18.2 and chi 2 = 23.1 for systolic and diastolic blood pressures, respectively, p less than 0.01). No differences were found between the performance of the two Spacelabs devices. Thus, although the absolute accuracy of blood pressure values provided by these monitors in ambulatory subjects is still limited, they seem to be suitable for studies aimed at assessing 24-hour blood pressure profiles quantitatively as well as qualitatively.

Adolescent↗
PubMed1992

Physical exercise in essential hypertension.

Although several studies have shown that physical training lowers blood pressure values both in normotensives and in hypertensives, the mechanisms accounted for this effect are not clearly elucidated. It has been reported that the decrease in blood pressure and heart rate that accompanies physical training is associated not only with an increase in vagal tone but also with a reduction in plasma norepinephrine levels. Whether this reduction really means a decrease in sympathetic neural discharge is unknown, however. To clarify this issue, we have performed in 7 normotensives direct recording of postganglionic muscle sympathetic nerve activity from the peroneal nerve by microneurography before and after 10 weeks of an endurance training which increased oxygen consumption by 10%. It was shown that the blood pressure lowering effect of the training program was accompanied by a marked reduction in resting sympathetic nerve activity. These data provide the first direct evidence that in man, the blood pressure reduction induced by physical training is mediated by the neural sympathetic mechanisms.

Blood Pressure↗
PubMed1992

Ambulatory blood pressure monitoring.

This paper reviews the evidence that, in patients with hypertension, end-organ damage correlates more closely with blood pressure values obtained by ambulatory blood pressure monitoring than with those obtained by conventional sphygmomanometry. However, ambulatory blood pressure monitoring is not suitable for routine use in the clinical setting because of a lack of standard reference values and data regarding the prognostic significance of this method. Ambulatory blood pressure values are reproducible and this method avoids the so-called placebo effect; thus, this method is useful in clinical studies investigating the efficacy and duration of action of antihypertensive drugs. Data from 1 study in which hypertensive patients were treated with slow release verapamil 240 mg, enalapril 20 mg, nitrendipine 20 mg and placebo, given once daily for 8 weeks according to a double-blind parallel group design, showed that mean 24-hour ambulatory blood pressure was reduced by all 3 drugs compared with placebo. Verapamil and enalapril showed similar antihypertensive efficacy and both drugs reduced night-time blood pressure more effectively than nitrendipine.

Blood Pressure Monitors↗
PubMed1992

Changes in 24 hour blood pressure and in cardiac and vascular structure in normotensive subjects with parental hypertension.

Subjects with family history of hypertension represent a suitable model to investigate the mechanisms responsible for early cardiovascular structural and functional changes occurring in essential hypertension. In our study we have addressed the factors involved in determining the mild elevation in office blood pressure frequently observed in normotensive subjects with hypertensive parents. In 15 normotensive subjects with both parents hypertensive (FH++) and in 15 normotensive subjects with one parent hypertensive (FH(+)-) we found no evidence of a hyperreactivity to stress as compared to the responses of 15 normotensive subjects with no parental hypertension (FH--). On the contrary FH++ subjects were characterized by a significant although mild increase in their blood pressure values recorded either at rest and in ambulatory conditions over the 24 hours, including night sleep. FH++ and FH(+)- subjects also showed a greater left ventricular mass thickness and a greater minimal forearm vascular resistance than FH-- subjects. Thus, the elevation in blood pressure found in the pre-hypertensive stage in subjects with positive family history for hypertension does not reflect a hyperreactivity to the stress associated with physician's visit but indicates an early and persistent blood pressure elevation. This blood pressure elevation is accompanied by early cardiovascular structural changes which may indicate that these subjects are exposed to a higher risk even before developing overt hypertension.

Adult↗
PubMed1992

Cigarette smoking and the adrenergic nervous system.

The acute increase in blood pressure and heart rate that accompanies cigarette smoking is associated with a rise in plasma catecholamines and it is thus believed to result from stimulation of the adrenergic nervous system. We have employed direct recording of efferent post-ganglionic sympathetic nerve activity by the microneurographic technique from the peroneal nerve to determine whether this stimulation occurs centrally or peripherally. It was shown that during cigarette smoking blood pressure, heart rate, plasma norepinephrine and epinephrine do increase markedly. Sympathetic nerve activity, however, shows a concomitant specular reduction. Thus peripheral (adrenal gland stimulation, reduction in norepinephrine reuptake, reduction in catecholamine clearance, etc.) rather than central mechanisms explain the adrenergic involvement in the acute hemodynamic effect of smoking, the central sympathetic drive being inhibited rather than excited probably as a result of arterial baroreceptor stimulation.

Blood Pressure↗
PubMed1992

Ambulatory blood pressure monitoring and antihypertensive treatment.

Ambulatory blood pressure monitoring is becoming increasingly popular among clinicians and investigators because of its potential to overcome the well-known limitations inherent to conventional blood pressure measurement. This paper will focus on the use of this approach in the evaluation of antihypertensive treatment. It will be argued that due to lack of prognostic validity and high cost, ABPM should not be employed routinely in treating hypertensives. It should always be employed, however, for the evaluation of the efficacy of new hypertensive drugs for which its superiority over sphygmomanometry is indisputable. This is exemplified by the results of a recent multicenter, double-blind, parallel group study on the effect of verapamil SR 240 mg, enalapril 20 mg and nitrendipine 20 mg and placebo, all administered once a day for eight weeks. Compared to placebo, all drugs reduced 24-hour mean blood pressure sufficiently. The reduction was evident throughout the daytime but nighttime blood pressure was more effectively lowered by verapamil and enalapril than by nitrendipine, documenting a difference that was not visible by using conventional measurements.

Ambulatory Care↗
PubMed1992

Ambulatory blood pressure monitoring in elderly patients with isolated systolic hypertension.

OBJECTIVES: This study compared clinic and ambulatory blood pressure measurement and the reproducibility of these measurements in older patients with isolated systolic hypertension (ISH). PATIENTS: Eighty-seven patients aged greater than or equal to 60 years with ISH on clinic measurement were followed in the placebo run-in phase of the Syst-Eur trial. METHODS: Clinic blood pressure was defined as the mean of two blood pressure readings on each of three clinic visits (six readings in total). Ambulatory blood pressure was measured over 24 h using non-invasive ambulatory blood pressure monitors. RESULTS: Daytime ambulatory systolic pressure was, on average, 21 mmHg lower than the clinic blood pressure, whereas diastolic pressure was, on average, similar with both techniques of measurement. In the 42 patients who had repeat measurements, clinic blood pressure levels nad the amplitude of the diurnal blood pressure profile (fitted by Fourier analysis) were equally reproducible. However, both were less reproducible than ambulatory blood pressure levels. The repeatability coefficients, expressed as per cent of near maximum variation (four times the standard deviation of a given measurement), were 52% and 45% for the clinic systolic and diastolic pressures, 56% and 42% for the amplitude of the diurnal profile, and 29% and 26% for mean 24-h pressures. CONCLUSIONS: In older patients with ISH, clinic and ambulatory systolic blood pressure measurements may differ largely: the prognostic significance of this difference remains to be elucidated. Furthermore, in these patients the level of pressure is more reproducible by daytime ambulatory blood pressure measurement than by clinic measurement.

Aged↗
PubMed1992

Effects of graded vasoconstriction upon the measurement of finger arterial pressure.

OBJECTIVE: To assess the effects of incremental phenylephrine infusion rates and subsequent graded vasoconstriction upon the performance of the Ohmeda Finapres. DESIGN: Blood pressure in eight hypertensive patients in the finger and the brachial artery was recorded simultaneously. Systolic blood pressure (SBP), diastolic blood pressure (DPB) and mean arterial pressure (MAP) were compared as well as additional waveform characteristics like the pressure at moment of the dicrotic notch and calculation of the pulsatile-systolic areas. RESULTS: Before phenylephrine infusion SBP and DBP were higher in the finger. At maximal infusion (1.6 micrograms/kg/min) the increase in brachial SBP was significantly underestimated by Finapres. Thus, the computed sensitivities of baroreflex control for SBP differed significantly between the two measurements. Under control conditions, the shape of the finger waveform differed from the brachial-artery waveform in terms of: (1) a more peaked appearance; (2) a dicrotic notch (Pnotch) which is located at a lower percentage of pulse pressure; and (3) a larger pulsatile-systolic area. At maximal infusion rates finger Pnotch increased whilst intrabrachial Pnotch did not. In contrast, the brachial and finger pulsatile-systolic areas changed fully in parallel. CONCLUSIONS: Phenylephrine infusion caused a significant, and clinically important, underestimation of the increase in brachial SBP when assessed by Finapres, whereas MAP and DBP and pulsatile-systolic area track intra-arterial pressure reliably.

Arteries↗
PubMed1992

Twenty-four hour blood pressure monitoring and end-organ damage.

Ambulatory blood pressure monitoring (ABPM) over 24 hours has become quite common. Evidence suggests that the mean 24-hour measurement is more closely associated with end organ damage, including end-points such as left ventricular hypertrophy (LVH), than is a single blood pressure measurement taken in the doctor's office. Clinicians disagree about the particular significance of blood pressure measurements obtained during exercise, blood pressure variability, and blood pressure load (a measurement above 140/90 over 24 hours). However, the morning peak in blood pressure appears to be associated with the highest incidence of coronary events, and end organ damage may be greater in subjects in whom nocturnal blood pressure falls only slightly from a diurnal baseline (non-dippers). From now, ABPM serves mainly as a research tool. Longitudinal controlled studies are needed to compare the value of ABPM to office blood pressure readings in terms of how these measurements can predict cardiovascular end-points or, more realistically, surrogate end-points, such as the development or regression of LVH.

Blood Pressure Determination↗