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Biomedical subjects

G Mancia

Publications and source records attributed to G Mancia.

At least 199 records · Page 11Linked to original sources
PubMed1997

Effect of sympathectomy on mechanical properties of common carotid and femoral arteries.

Sympathetic stimulation is accompanied by a reduction of arterial distensibility, but whether and to what extent elastic and muscle-type arterial mechanics is under tonic sympathetic restraint is not known. We addressed this issue by measuring, in the anesthetized rat, the diameters of the common carotid and femoral arteries with an echo-Doppler device (NIUS 01). Blood pressure was measured by a catheter inserted contralaterally and symmetrically to the vessel where the diameter was measured. Arterial distensibility over the systolic-diastolic pressure range was calculated according to the Langewouters formula. Data were collected in 10 intact (vehicle pretreatment) and 9 sympathectomized (6-hydroxydopamine pretreatment) 3-month-old Wistar-Kyoto rats. Compared with the intact animals, sympathectomized rats showed a marked increase in arterial distensibility over the entire systolic-diastolic pressure range. When quantified by the area under the distensibility-pressure curve, the increase was 59% and 62% for the common carotid and femoral arteries, respectively (P<.01 for both). In the femoral but not in the common carotid artery, sympathectomy was accompanied also by an increase in arterial diameter (+18%, P<.05 versus intact). Therefore, in the anesthetized normotensive rat, sympathetic activity exerts a tonic restraint on large-artery distensibility. This restraint is pronounced in elastic vessels and even more pronounced in muscle-type vessels.

Animals↗
PubMed1997

Sympathetic activity, blood pressure variability and end organ damage in hypertension.

Animal studies have provided clearcut evidence that sympathetic factors are involved in the development and maintenance of high blood pressure (BP). This also appears to be the case in humans, in which sympathetic activation, detected through plasma noradrenaline measurement, noradrenaline spillover technique and direct recording of muscle sympathetic nerve activity, has been shown to characterize the early phases of the hypertensive state and parallel its severity. Sympathetic factors also play in a variety of pathophysiological states frequently associated with hypertension, such as obesity, insulin resistance and atherosclerosis. In addition evidence has been collected that adrenergic factors represent one of the mechanisms involved in determining BP variability, which is strictly associated with end organ damage. Taken together these findings underline the importance that the therapeutical approach to hypertension is aimed not only at lowering BP but also at reducing sympathetic activity.

Animals↗
PubMed1997

[Secondary prevention of stroke through arterial blood pressure reduction].

Large scale observational studies have conclusively demonstrated that systolic and diastolic blood pressure values are linearly related to the incidence of cerebrovascular diseases and that high blood pressure is an important risk factor for both primary and secondary development of stroke. Interventional studies have shown that blood pressure lowering by antihypertensive treatment reduces the incidence of stroke in hypertensive patients without a history of previous stroke. Whether this is the case also for the secondary prevention of cerebral ischemic attacks has not been unequivocally shown, however. The PROGRESS ("Perindopril Protection Against Recurrent Stroke Study") study has been designed and is under way to collect information on this important issue of the antihypertensive treatment, its purpose being to evaluate the blood pressure lowering effects with an ACE-inhibitor on recurrent stroke in an overall population of 6000 patients with a positive history of previous cerebral ischemic attacks or stroke.

Cerebrovascular Disorders↗
PubMed1997

The sympathetic nervous system in human hypertension.

While animal models of hypertension have clearly shown an increase in sympathetic activity, a similar demonstration in humans has been more difficult to obtain for methodological reasons. There is now clear evidence, however, of an increase sympathetic activity in essential hypertension by the finding of either an increase in plasma norepinephrine and an increase in muscle sympathetic nerve traffic. Among the mechanisms responsible for this sympathetic activation the arterial baroreflex may play a role although probably a non specific and late one. Central neural influences associated with an excessive hypothalamic response to stress may also be involved, but conclusive evidence is still lacking due to the difficulty of assessing cardiovascular reactivity to stress in man. A deeper insight into the features of human sympathetic cardiovascular control may be offered now by new techniques which allow neural cardiovascular regulation to be assessed in daily life through computer analysis of noninvasive ambulatory beat-by-beat blood pressure and heart rate recordings.

Animals↗
PubMed1997

[Antihypertensive therapy: why and how?].

Many clinical trials have shown that lowering increased blood pressure by an antihypertensive agent reduces the risk of morbidity and mortality due to hypertension. Despite these beneficial effects, several questions remain largely unanswered, particularly with respect to the degree of cardiovascular protection conferred by the antihypertensive complications. This article addresses some of these questions by reviewing the recommended means of lowering the blood pressure in hypertensive patients. The clinical value of effective blood pressure control throughout the 24 hour period is discussed together with the therapeutic strategies available to obtain this objective.

Antihypertensive Agents↗
PubMed1997

Critical appraisal of indices for the assessment of baroreflex sensitivity.

The sequence technique and the spectral estimation of the alpha coefficient are currently employed for the assessment of "spontaneous" baroreflex sensitivity (BRS). The comparison of performance and effectiveness of these techniques is obtained by the analysis of systolic blood pressure (SBP) and pulse interval (PI) tracings recorded in conscious cats before and after baroreceptor denervation. Results indicate that (1) the average BRS estimates obtained by the sequence technique and by the alpha coefficient at the respiratory frequency are similar, (2) the alpha coefficients computed at the respiratory frequency tend to be higher than alpha coefficients estimated at 0.1 Hz, and (3) in spite of what is traditionally claimed, the PI-SBP coherence does not seem to represent a reliable parameter to enhance the specificity of the spectral estimate, because coherence values often remain above the 0.5 threshold also after baroreceptor denervation.

Animals↗
PubMed1997

Blood pressures other than the one at the clinic.

While assessing the cardiovascular risk of hypertensive patients, different types of blood pressure measurements can be regarded as suitable surrogate endpoints. In this context the possible role of clinic, stress, exercise, basal, home and ambulatory blood pressures is briefly discussed. The clinical value of night-time blood pressure, of the clinic-daytime blood pressure difference and of blood pressure variability is also addressed.

Blood Pressure↗
PubMed1997

Clinical value of blood pressure variability.

Blood pressure (BP) is known to continuously fluctuate over time and both the amplitude and frequency of these changes have been reported to be clinically relevant. Indeed, it has been shown that the occurrence of pronounced BP changes at the time of the physician's visit may introduce errors in the diagnosis of hypertension and in the assessment of the efficacy of antihypertensive treatment. Moreover, several studies have provided evidence that the end organ damage of hypertension is not only more closely related to 24h average BP values than to casual BP readings, it is also significantly and independently related to the degree of BP variability during the day and night. Results from a recent follow-up study support the possibility that the degree of BP variability may also have prognostic relevance in hypertensive patients. Recent progress in technology has offered us non-invasive techniques for the assessment of beat-to-beat finger blood pressure variability and for the detailed quantification of all its frequency components from the fastest to the slowest ones. Their role as additional surrogate endpoints in essential hypertension needs to be addressed in future studies.

Blood Pressure↗
PubMed1997

[The difference between clinical ambulatory measured blood pressure and daily monitored pressure does not reflect the "white coat effect"].

The difference between clinic and average daytime ambulatory blood pressure is frequently used to identify patients with "white coat" hypertension (i.e. with a pronounced pressor response to the clinical evaluation) although there is no evidence that this difference is indeed due to a white coat effect. In 28 mild hypertensive outpatients, the blood pressure was continuously recorded by a noninvasive finger device before and during the doctor's visit. The peak blood pressure increase, recorded during the visit was compared with the difference between clinic and daytime average ambulatory blood pressure. Peak increases in systolic and diastolic finger blood pressure during the doctor's visit were 38.2 +/- 3.1 mmHg and 20.7 +/- 1.6 mmHg, respectively compared to pre visit values (means +/- standard error, both p < 0.01). Daytime average systolic and diastolic blood pressure were 135.5 +/- 2.5 mmHg and 89.2 +/- 1.9 mmHg, both being lower than the corresponding clinic blood pressure values (146.6 +/- 3.6 mmHg and 94.9 +/- 2.2 mmHg, p < 0.01). Their differences, however, were < 30% of the peak finger blood pressure increase during the physician's visit. While the physician's visit was associated with tachycardia (+9.0 +/- 1.6 b/min, p < 0.01) there was no difference between clinic and daytime average heart rate. The alerting reaction and the pressor response induced by the physician's visit is not reflected by the difference between clinic and daytime average blood pressure. Such a difference is not therefore a reliable measure of the white coat effect.

Adult↗
PubMed1996

Neural cardiovascular regulation and 24-hour blood pressure and heart rate variability.

The availability of ambulatory intraarterial blood pressure monitoring techniques offers a deeper insight into the features of blood pressure variability over 24 hours and allows better understanding of the mechanisms responsible for the continuous and marked blood pressure changes that occur throughout the day and at night. Among these mechanisms, central and reflex neural influences play a major role. This has led to the development of techniques for the assessment of 24-hour "spontaneous" baroreflex sensitivity through combined computer analysis of blood pressure and heart rate variations in the time or frequency domain. The recent introduction of continuous noninvasive ambulatory blood pressure monitors offers the unique possibility of obtaining dynamic information on neural cardiovascular control in clinical conditions in which the assessment of autonomic cardiovascular regulation may have diagnostic and prognostic implications.

Blood Pressure↗
PubMed1996

Impaired radial artery compliance in normotensive subjects with familial hypercholesterolemia.

Hypercholesterolemia impairs arteriolar dilatation, but whether the vascular abnormalities accompanying this condition include large artery function is unknown. We addressed this issue in 13 normotensive subjects with familial hypercholesterolemia (serum cholesterol 401.6 +/- 16.9 mg/dl, mean +/- S.E., FHC) and no evidence of atherosclerotic lesions, in whom radial artery (RA) diameter and blood pressure (BP) were measured beat to beat by an echotracking and a Finapres device, respectively. RA compliance (RAC) was derived from the diameter/BP relationship and expressed over the systo-diastolic BP range, both at baseline and after a 12-min brachial artery occlusion. RAC was expressed also as the area under the RAC/BP curve divided for pulse BP. Measurements included maximal forearm blood flow (plethysmography) and minimal forearm vascular resistance (FVR) which were obtained from the values following the 12-min brachial arterial occlusion. Data were collected before and after 6- and 24-month lipid lowering treatment (simvastatin 40 mg/day). Ten age-matched normotensive normocholesterolemic healthy subjects (N) served as controls. Compared to N, baseline RAC was strikingly reduced in FHC (-53.5%, P < 0.01). After ischemia RAC increased significantly and markedly in N (+38.7, P < 0.01), while only a modest and non-significant increase was observed in FHC. Minimal FVR was markedly higher in FHC than in N (3.5 +/- 0.9 vs 1.6 +/- 0.1 units, P < 0.01). In FHC (7 subjects) RAC remained unchanged after 6 months of lipid lowering treatment, but increased markedly (+55.2%, p < 0.05) when treatment was prolonged to 24 months. Lipid lowering treatment also reduced minimal FVR, the effect being significant both after 6 and after 24 months. No changes in RAC and minimal FVR were seen after 6 months in controls. Thus, in subjects with a marked increase in serum cholesterol due to FHC, not only arteriolar dilatation, but also RAC and distensibility are markedly impaired. This impairment can be favourably affected by an effective lipid lowering treatment of long duration.

Anticholesteremic Agents↗
PubMed1996

Blood pressure and heart rate variability in autonomic disorders: a critical review.

Spectral analysis (SA) of blood pressure (BP) and heart rate (HR) fluctuations has been proposed as a unique approach to obtain a deeper insight into cardiovascular regulatory mechanisms in health and disease. A number of studies performed over the last 15 years have shown that autonomic influences are involved in the modulation of fast BP and HR fluctuations (with a period <1 min), particularly at frequencies between 0.2 and 0.4 Hz [high frequency (HF) region or respiratory frequency] and around 0.1 Hz [mid frequency (MF) region]. In patients with secondary or primary autonomic dysfunction, SA of BP and HR signals recorded at rest or during orthostatic challenge in a laboratory environment have shown the occurrence of a reduction in the power of MF and/or HF, BP and HR components. Such a reduction is associated or may even precede the clinical manifestation of autonomic neuropathy. However, the above results collected in standardized laboratory conditions cannot reflect the features of neural cardiovascular control during daily life in ambulant individuals with autonomic failure. To investigate this issue, SA techniques have been applied to 24 h beat-to-beat intra-arterial and non-invasive finger BP recordings obtained in elderly subjects and in pure autonomic failure patients, respectively. In these conditions, HR powers displayed a reduction over a wide range of frequencies (from 0.5 to below 0.01 Hz). Conversely, BP powers underwent a complex rearrangement characterized by a reduction in the power around 0.1 Hz and by an increase in the powers at the respiratory frequency and at frequencies below 0.01 Hz. Dynamic quantification of the sensitivity of the baroreceptor-heart rate reflex by combined analysis of systolic BP and pulse interval (i.e. the interval between consecutive systolic peaks) powers around 0.1 Hz (alpha technique) has shown that in elderly subjects, and even more so in pure autonomic failure patients, baroreflex sensitivity is markedly reduced over the 24 h, and is no longer characterized by its physiological day-night modulation. In conclusion, although in some instances SA of cardiovascular signals may fail to fully reflect the features of autonomic cardiovascular control, the evidence discussed clearly demonstrates that this approach represents a promising tool for a dynamic assessment of the early impairment of neural circulatory control in autonomic failure. This is particularly the case when these analyses are performed on 24 h continuous BP and HR recordings in ambulant subjects.

Autonomic Nervous System Diseases↗
PubMed1996

Effects of sino-aortic denervation on spectral characteristics of blood pressure and pulse interval variability: a wide-band approach.

Sino-aortic denervation (SAD) is employed in cats to evaluate the baroreflex influence on blood pressure (BP) and pulse interval (PI) spectral components from 0.00008 to 0.9 Hz as assessed by FFT wide-band spectra and their 1/f modelling; and the linear coupling between BP and PI and between systolic and diastolic BP as assessed by coherence analysis. Specific procedures have been developed to obtain an effective smoothing of spectra and coherence functions. SAD induced an increase in BP powers from 0.03 to 0.0006 Hz and a power reduction of most of the remaining BP components; a reduction of PI powers at all frequencies; marked deviations of BP spectra from the 1/f trend; a reduction of the coherence between BP and PI from 0.12 to 0.5 Hz and a coherence enhancement at lower frequencies. These findings indicate that the arterial baroreflex modulates both fast and slow spectral components of BP and PI; homogeneously enhances PI fluctuations at all frequencies; produces differentiated effects on BP fluctuations along the frequency axis; and at low frequencies exerts the buffering action on BP through strategies which reduce the BP-PI linear link.

Animals↗
PubMed1996

Benefit and costs of anti-hypertensive treatment.

Hypertension is common throughout the world and represents the single greatest risk factor for increasing cardiovascular mortality, cardiovascular morbidity and overall mortality. Diseases associated with hypertension are not only, in general, of a chronic disabling nature, but, in most instances, require frequent hospitalization, with expensive drug treatment and management. Stroke, coronary heart disease, congestive heart failure and chronic renal insufficiency represent the most commonly encountered corollaries of inadequately treated hypertension. Anti-hypertensive treatment is accompanied by a reduction of hypertension-related cardiovascular risk and a clearcut benefit in terms of reduced incidence of major cardiovascular complications of hypertension and overall mortality. This benefit has frequently been underestimated in many clinical trials. Attempts to improve the cost-benefit ratio have included the use of treatment strategies based upon 24-h control of blood pressure, since it has been demonstrated that hypertension-related end-organ damage correlates more closely with 24-h average blood pressure and with 24-h blood pressure variability than with blood pressure measured in the clinic. It is hoped that new anti-hypertensive agents, which smoothly reduce 24-h blood pressure profile, will further reduce the incidence of hypertension-related end-organ damage.

Antihypertensive Agents↗