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Biomedical subjects

G Mancia

Publications and source records attributed to G Mancia.

At least 253 records · Page 14Linked to original sources
PubMed1995

Spectral analysis of blood pressure and heart rate variability in evaluating cardiovascular regulation. A critical appraisal.

Blood pressure variability includes rhythmic and nonrhythmic fluctuations that, with the use of spectral analysis, appear as clear peaks or broadband power, respectively. This review offers a concise and critical description of the spectral methods most commonly used (fast Fourier transform versus autoregressive modeling, time-varying versus broadband spectral analysis) and an evaluation of their advantages and disadvantages. It also provides insight into the problems that still affect the physiological and clinical interpretations of data provided by spectral analysis of blood pressure and heart rate variability. In particular, the assessment of blood pressure and heart rate spectra aimed at providing indexes of autonomic cardiovascular modulation is discussed. Evidence is given that multivariate models--which allow evaluation of the interactions between changes in blood pressure, heart rate, and other biological signals (such as respiratory activity) in the time or frequency domains--offer a more comprehensive approach to the assessment of cardiovascular regulation than that represented by the separate analysis of fluctuations in blood pressure or heart rate only.

Autonomic Nervous System↗
PubMed1995

Sympathectomy and cardiovascular spectral components in conscious normotensive rats.

We examined the extent to which sympathetic influences are reflected by spectral powers of blood pressure and pulse interval in specific frequency bands in spontaneously behaving Wistar-Kyoto rats subjected to continuous intraarterial blood pressure recording. The rats were pretreated with 6-hydroxydopamine (150 mg/kg twice in 1 week, n = 19) to produce chemical sympathectomy or received vehicle (n = 15). In the sympathectomized group, additional monitoring sessions were performed with rats under alpha-adrenergic receptor blockade with phenoxybenzamine (n = 8), beta-receptor blockade with propranolol (n = 7), or cholinergic receptor blockade with atropine (n = 8). Blood pressure signals were analyzed by a computer to calculate spectral powers (fast Fourier transform) in the low-frequency (0.025 to 0.1 Hz), mid-frequency (0.1 to 0.6 Hz), and high-frequency (0.8 to 3.0 Hz) bands. In sympathectomized rats, low-frequency power of blood pressure was 70% greater than in intact rats, whereas mid-frequency power was 60% smaller (P < .05 for both) and high-frequency power was unchanged. High-frequency power of pulse interval was also unchanged in sympathectomized rats, whereas low- and mid-frequency powers were reduced by approximately 50% (P < .05). No further alterations in spectral powers were observed by adding alpha- or beta-adrenergic blockade to sympathectomy, whereas adding cholinergic blockade caused a striking reduction in all pulse interval powers. Thus, mid-frequency blood pressure power depends on sympathetic but also to a substantial extent on nonsympathetic influences. Sympathetic influences do not contribute to low-frequency blood pressure power, having instead a restraining effect. The low- and mid-frequency pulse interval powers depend on both sympathetic and vagal influences. Thus, no blood pressure or pulse interval power in the mid- and low-frequency ranges can be regarded as a specific marker of sympathetic activity.

Adrenergic alpha-Antagonists↗
PubMed1995

Sympathetic modulation of radial artery compliance in congestive heart failure.

Animal studies have suggested that arterial compliance can be modulated by adrenergic influences. Whether this adrenergic modulation also occurs in humans is still a matter of debate. In the present article we address this issue by examining the relationships between sympathetic tone and arterial compliance in a variety of physiological and pathophysiological conditions. We have found that cigarette smoking, ie, an action that produces a marked sympathetic activation, causes a significant reduction in radial artery compliance, as measured by an echotracking device capable of providing continuous beat-to-beat evaluation of this hemodynamic variable. When expressed as compliance index, ie, as the ratio between the area under the compliance-pressure curve and pulse pressure, the reduction amounted to 35.7 +/- 4.8% (mean +/- SEM) and was independent of the smoking-related blood pressure increase. Furthermore, pharmacological stimulation of adrenergic receptors located in the arterial wall was also shown to affect arterial compliance because the radial artery compliance index was markedly reduced (- 29.5 +/- 3.9%) during phenylephrine infusion in the brachial artery at doses devoid of any systemic blood pressure effect. Evidence was also obtained that the relationship between sympathetic activation and arterial compliance has pathophysiological relevance, because in 17 patients with congestive heart failure (New York Heart Association classes II through IV) there was a significant inverse correlation (r = .62, P < .01) between muscle sympathetic nerve activity (directly measured by microneurography in the peroneal nerve) and radial artery compliance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Angiotensin-converting enzyme inhibition and radial artery compliance in patients with congestive heart failure.

Congestive heart failure is characterized by a clear-cut impairment of arterial compliance of medium-sized arteries, but whether this alteration is irreversible or can be favorably affected by cardiovascular drugs currently used in congestive heart failure treatment is unknown. We studied 9 congestive heart failure patients (New York Heart Association class II; age, [mean +/- SEM] 60.7 +/- 3.3 years) receiving diuretic and digitalis treatment in whom arterial compliance was assessed at the level of the radial artery by an echotracking device capable of measuring the arterial diameter along the entire cardiac cycle. Beat-to-beat arterial blood pressure was concomitantly measured by a Finapres device that allowed diameter-pressure curves and compliance-pressure curves (Langewouters' formula) to be calculated for the entire systolic-diastolic blood pressure range. Arterial compliance was expressed as the area under the compliance-pressure curve normalized for pulse pressure (compliance index). Data were collected before and after 4 and 8 weeks of oral administration of benazepril (10 mg/day). Ten healthy subjects were studied before and after an observational period of 4 weeks (5 subjects) or 8 weeks (5 subjects), and 9 age-matched mildly essential hypertensive subjects studied before and after 4 to 12 weeks of benazepril administration served as control subjects. In congestive heart failure patients, baseline compliance index was significantly less than in normotensive and hypertensive subjects. However, the compliance index showed a marked increase after 4 weeks of benazepril administration (+95.7 +/- 24.9%, P < .05); the increase was also marked after 8 weeks of angiotensin-converting enzyme inhibitor treatment (+77.7 +/- 4.2%, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Radial artery compliance in young, obese, normotensive subjects.

Obesity is characterized by a number of cardiovascular alterations, and whether these alterations involve arterial compliance is unknown. In 12 young, obese, normotensive subjects (age, 23.9 +/- 1.3 years; mean +/- SEM) and 12 age- and sex-matched lean control subjects we measured blood pressure, radial artery diameter, and radial artery compliance continuously over the systodiastolic pressure range with a Finapres device and recently developed echo-tracking device. Measurements were obtained at baseline and after prolonged ischemia, that is, when diameter and compliance are increased. Blood pressure values were normal in both groups (obese subjects: 109.2 +/- 4.9/68.2 +/- 2.7 mm Hg; lean control subjects: 108.2 +/- 4.1/60.7 +/- 3.8 mm Hg), but in addition to a marked increase in body mass index (38.5 +/- 0.8 versus 23.1 +/- 0.9 kg/m2, P < .01), obese subjects showed a slight and nonsignificant increase in heart rate (71.1 +/- 3.2 versus 66.7 +/- 3.3 beats per minute, P = NS), increases in left ventricular wall thickness and left ventricular mass index (121.5 +/- 4.8 versus 103.4 +/- 3.3 kg/m2, P < .01), no changes in plasma renin activity and plasma norepinephrine (compared with normal values), and a marked reduction in total body glucose uptake (glucose clamp technique). Obese subjects showed radial artery diameter and compliance values that were greater than those seen in control subjects throughout the systodiastolic pressure range. The differences were 13% (P < .05) and 96% (P < .01), respectively, and both diameter and compliance remained higher in obese than lean subjects after forearm ischemia. In obese and lean subjects baseline radial artery diameter values correlated highly with body weight, body surface area, and body mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Blood pressure variability and its implications for antihypertensive therapy.

Although it is clear that antihypertensive treatment is beneficial in reducing stroke morbidity and mortality, the results of the major outcome studies show less impact on coronary heart disease. Studies utilizing 24-h blood pressure (BP) monitoring show a positive association between target organ damage and the level of 24-h BP, and with variability in BP, which is an independent determinant of target organ damage. Current understanding of the pathogenesis and pathophysiology of coronary heart disease suggests that optimal antihypertensive treatment should ensure the following: effective 24-h BP control, smooth antihypertensive effect with reduced variability; attenuation of the early morning surge in BP; maintenance of the normal circadian pattern of BP; effective therapeutic coverage in the face of suboptimal compliance; and lack of reflex activation of the sympathetic nervous system. On the basis of our current understanding, this optimum is most likely to be achieved by the use of antihypertensive agents with a long duration of action.

Antihypertensive Agents↗
PubMed1995

Ambulatory blood pressure monitoring in the evaluation of antihypertensive treatment: additional information from a large data base.

Aims of our study were i) to compare in a large number of hypertensive subjects the relative effect of antihypertensive treatment on clinic (C) blood pressure (BP) and various ambulatory (A) BP components, and ii) to determine whether antihypertensive treatment affects BP variability. In 266 mild essential hypertensive outpatients (age: 18-78 years) CBP (trough measurements) and ABP (Spacelabs 90202 or 90207) were measured after 3 to 4 weeks of wash-out and after 4 to 8 weeks of treatment with an ACE-inhibitor (n = 135) or a calcium-antagonist (n = 131). ABP recordings were analyzed to obtain average 24 h, day-time (6 a.m. to midnight) and night-time (midnight to 6 a.m.) systolic and diastolic BP values and standard deviations (BP variabilities). Treatment reduced both CBP and ABP. Treatment-induced changes in CBP showed a poor correlation with those in 24h, day- and night-time BP (r never > 0.23) and the correlation was poor also when trough ABP (mean of last 2 h) was considered. Twenty-four hour, day- and night-time BP were similarly reduced by treatment with a direct relationship between the initial BP values and the subsequent BP falls. BP standard deviations were also reduced by treatment in relation to the pretreatment values but the overall reduction was small, limited to the day-time and proportional or less than proportional to the reduction in mean values, with no changes or an increase in variation coefficients. The effects of ACE-inhibitor and calcium-antagonist treatments were superimposable. Our results from a large data base show that antihypertensive treatment effectively reduces all ABP components. The reduction cannot be predicted by the concomitant fall in CBP but it relates to the initial ABP values. Treatment has a limited effect on BP variability, this being the case both for ACE-inhibitors and calcium-antagonists.

Adolescent↗
PubMed1995

Improving the management of hypertension in clinical practice.

Antihypertensive therapy is unquestionably beneficial, but current management of hypertension does not reduce cardiovascular risk to normotensive levels. Treatment of the hypertensive patient may be improved by a number of measures. These include control of SBP as well as DBP, with reduction to < 140/90 mmHg. Treatment of concomitant diseases and of other risk factors is likely to be of benefit, as is 24 h control of BP. Variability of BP appears to influence clinical outcome, but it is unclear whether this can be reduced by treatment. Poor patient compliance with treatment instructions may be an important factor in disappointing therapeutic performance, but could be improved with less complex treatment regimens.

Antihypertensive Agents↗
PubMed1995

Cardiac and vascular structural changes in normotensive subjects with parental hypertension.

OBJECTIVE: To evaluate whether a predisposition to hypertension is associated with early cardiac and vascular alterations. SUBJECTS: Twenty-five normotensive subjects with both parents hypertensive (group 1) and 28 age- and sex-matched control subjects with both parents normotensive (group 2). METHODS: In the two groups the measurements included: clinic blood pressure; left ventricular end-diastolic diameter, septal wall thickness and posterior wall thickness (by echocardiography); minimal forearm and calf vascular resistances (i.e. resistance assessed immediately after prolonged ischaemia, which depends on arteriolar wall thickness); and baseline and postischaemic radial artery compliance-pressure curves over the systolodiastolic pressure range (by echotracking device and finger blood pressure). RESULTS: Group 1 had a slightly higher clinic blood pressure, and septal and posterior wall thickness, than group 2. Minimal forearm vascular resistance was clearly greater in group 1 than in group 2, whereas minimal calf vascular resistance was not significantly different in the two groups. Radial artery compliance was also similar in the two groups. CONCLUSIONS: Parental predisposition to hypertension is accompanied by cardiac and arteriolar structural changes qualitatively similar to those found in hypertensive patients, although arteriolar structural changes do not involve all vascular beds. Arterial compliance is not altered in this condition. Vascular changes may be determined by mechanisms other than blood pressure elevation.

Adult↗
PubMed1995

[Changes in the compliance of the radial artery in normotensive subjects with familial hypercholesterolemia].

BACKGROUND: Recent studies have shown that in normotensive hypercholesterolemic subjects endothelial dependent dilatation of arterioles is impaired. METHODS: We studied the effects of hypercholesterolemia on arterial compliance in normotensive subjects of both sexes, with a normal serum cholesterol (n = 8, total serum cholesterol = 209 +/- 7 mg/dl, means +/- SEM), an elevated serum cholesterol (n = 8, 285 +/- 8 mg/dl) and familial hypercholesterolemia (n = 8, 393 +/- 20 mg/dl). All subjects were normotensive and devoid of clinical and laboratory evidence of atherosclerotic lesions. The mean age of the 3 groups was 46.7 +/- 2.5, 51.5 +/- 2.9 and 49.8 +/- 2.9 years respectively. In hypercholesterolemic subjects use of hypolipidemic drugs was stopped 2 months before the study. Arterial compliance was measured from the radial artery by an echo-tracking device capable of providing radial artery diameter and, with the addition of a Finapres device, diameter/pressure and compliance/pressure curves continuously over the systolic-diastolic blood pressure range. RESULTS: Mean arterial pressure was similar in the three groups (84.5 +/- 6.1, 79.8 +/- 2.4 and 73.1 +/- 4.4 mm Hg). Arterial compliance was similar in normocholesterolemic and non familial hypercholesterolemic subjects but it was strikingly reduced (50%) in familial hypercholesterolemic subjects. The reduction was even more evident following prolonged local ischemia because while in the first two groups arterial compliance increased after ischemia, in familial hypercholesterolemia no increase occurred. CONCLUSIONS: Thus, familial hypercholesterolemia is accompanied by a striking CONCLUSIONS: Thus, familial hypercholesterolemia is accompanied by a striking reduction in radial artery compliance, i.e. a marked increase in arterial wall stiffness. This may increase the traumatic effect of blood pressure on the arterial wall, favouring atherosclerosis. The lack of compliance alterations in non familial hypercholesterolemia suggests that this hemodynamic disturbance either occurs when serum cholesterol is more markedly increased or it has a genetic origin.

Analysis of Variance↗
PubMed1995

[The intervention trial in the evaluation of antihypertensive therapy].

Several epidemiological studies carried out over the past 30 years have unequivocally shown that hypertension is a major risk factor for cardiovascular diseases, the incidence of cerebral, coronary, and peripheral artery disease being progressively higher as blood pressure values become more and more elevated. Interventional clinical trials have also shown that antihypertensive treatment is able, by decreasing high blood pressure values, to reduce the cardiovascular risk profile of the hypertensive patient, although not to normalize it. Furthermore, antihypertensive treatment has been demonstrated to be more effective in protecting against stroke and congestive heart failure than against coronary artery disease. This paper will review the results of the various interventional trials carried out in hypertensive states of different clinical severity and in isolated systolic hypertension of the elderly. It will also briefly discuss the peculiar features of the ongoing interventional clinical trials, whose results will allow clarification of important and still unsolved issues concerning antihypertensive therapy.

Aged↗
PubMed1995

[The role of the sympathetic nervous system in essential arterial hypertension and organ damage].

Experimental evidence collected in animals and man supports the concept that adrenergic neural factors may be involved in the development of the hypertensive state and hypertension-related cardiovascular and metabolic complications. The various methodological approaches employed in evaluating sympathetic tone in man have shown that a hyperadrenergic state is evident in the early hypertensive phases. Sympathetic activation becomes more evident in stable hypertension and contributes to the maintenance of high blood pressure values. Adrenergic factors are also involved in the pathogenesis of cardiac and vascular hypertrophy, i.e. cardiovascular hypertensive complications that in the past have been regarded as mainly dependent on hemodynamic mechanisms. Sympathetic overactivity may also play an important role in the atherogenic process and may contribute to the insulin resistance state that often characterizes the hypertensive patient. The role of neural sympathetic factors in the pathophysiology of hypertension and its complications suggests that modulation of sympathetic activity should be an important target of modern antihypertensive treatment, aimed not only at lowering blood pressure, but also at reducing the patient's cardiovascular risk profile.

Animals↗
PubMed1995

Diurnal blood pressure profile in older patients with isolated systolic hypertension. The SYST-EUR Investigators.

This study describes the diurnal blood pressure (BP) profile and identifies its correlates in older patients with isolated systolic hypertension (ISH). The ambulatory BP readings of 408 patients, aged > or = 60 years, with ISH on clinic measurement, enrolled in the placebo run-in phase of the Syst-Eur Trial were examined. The time-weighted 24 h BP, daytime and night-time BP and the cusum-derived crest and trough BP were computed to express the BP level. The daily alteration between the high and low BP span was estimated from the day-night BP difference, the cusum derived circadian alteration magnitude and plot height, as well as the amplitude of the Fourier curve. The 24 h SBP and DBP tended to be higher in men (150 +/- 15/82 +/- 9 mm Hg) than in women (147 +/- 17/79 +/- 10 mm Hg), but the sex difference was only significant for DBP. In multiple regression analysis, the 24 h SBP increased (P < 0.05) by 3 mm Hg for each 10 year increment in age and was also 10 mm Hg higher (P < 0.001) in smokers than in non-smokers; the 24 h DBP was 2 mm Hg higher (P < 0.05) in men than in women and decreased (P < 0.05) by 1.5 mm Hg for each 10 year increment in age. The day-night difference in SBP increased with 2 mm Hg for each 10 mm Hg increase in the conventional pressure, decreased with 5 mm Hg for each 10 year increment in age and was 6 mm Hg higher in smokers than in non-smokers; the day-night difference in diastolic pressure was 2 mm Hg greater in women than in men. We conclude that the main determinants of the diurnal BP variation in older patients with isolated systolic hypertension were sex, age, smoking habits and the level of pressure on conventional measurement.

Age Distribution↗
PubMed1995

Ambulatory blood pressure normality: results from the PAMELA study.

OBJECTIVE: To determine ambulatory and home blood pressure means and distributions in relation to clinic blood pressure in a general population. METHODS: We obtained a random sample of 2400 subjects stratified by sex and 10 year age groups to be representative of residents aged 25-64 years of the city of Monza. Participation rate was 69% (1651 subjects). Blood pressure measurements consisted of clinic blood pressure (average of three measurements, sphygmomanometry), home blood pressure (average of morning and evening measurements, semiautomatic device) and ambulatory blood pressure (automatic readings at 20 min intervals, Spacelabs 90207). Clinic blood pressure was obtained both before and after home and ambulatory blood pressures. Data analysis did not include 213 subjects receiving antihypertensive drug treatment and was therefore limited to 1438 participants. RESULTS: In the 1438 subjects, clinic, home and ambulatory blood pressure showed a normal-like distribution, with a taller peak and a narrower base for ambulatory than for home and clinic values. Clinic, home and ambulatory blood pressures were significantly related to each other (P always < 0.001). The means of the two clinic blood pressures obtained on consecutive days were superimposable (127.4 +/- 17.0/82.3 +/- 9.8 and 128.2 +/- 16.5/81.9 +/- 9.9 mmHg) and both were markedly higher than home and 24 h average blood pressures (8.2 mmHg), which were similar to one another. The differences between clinic and home or 24 h average blood pressure were similar in both sexes but increased with increasing age and clinic blood pressure values. The influence of clinic blood pressure values on the clinic-ambulatory or clinic-home blood pressure differences was more important than age. Although higher than the 24 h average value, daytime average blood pressure was also lower than clinic blood pressure. Night-time blood pressure was markedly lower than the daytime value in both sexes and at all ages. CONCLUSION: Data from a large and unbiased sample of a general population show that home and 24 h or daytime average blood pressures are much lower than clinic blood pressure. The relatively close correlation between blood pressure values measured with the different methods used has allowed calculation of home and ambulatory blood pressure values corresponding to the accepted upper limit of normality of clinic blood pressure (140/90 mmHg). The upper limit of normality for the population was for both home and ambulatory blood pressures in the range 120-130 and 75-81 mmHg for systolic and diastolic values, respectively, with slight differences depending on sex and age. Taking 140/90 mmHg as the upper normal limit of the population is therefore an error that leads to individuals whose home or ambulatory blood pressures are high being considered as normotensive.

Adult↗
PubMed1995

Sympathetic, parasympathetic and non-autonomic contributions to cardiovascular spectral powers in unanesthetized spontaneously hypertensive rats.

OBJECTIVE: To determine whether spectral powers of blood pressure and pulse interval can specifically reflect sympathetic and parasympathetic effects in unanesthetized, free-moving spontaneously hypertensive rats (SHR). DESIGN: Spectral powers were observed before and after various autonomic interventions in chronically instrumented rats. MATERIALS AND METHODS: Chemical sympathectomy was produced in 12-week-old SHR by repeated injections of 6-hydroxydopamine, while control rats were given vehicle alone. Chronic arterial and venous catheters were inserted in the femoral artery and vein. Blood pressure was recorded beat-to-beat for 90 min in free-moving rats; further recording sessions were obtained under additional alpha-receptor blockade with phenoxybenzamine at 1 mg/kg and/or additional cholinergic blockade with atropine at 0.8 mg/kg. Off-line computer analysis (fast Fourier transform) provided estimates of low- (0.025-0.1 Hz), mid- (0.1-0.6 Hz) and high-frequency (0.8-3.0 Hz) powers for blood pressure and pulse interval over consecutive periods of 100 s. RESULTS: The most noticeable findings were that sympathectomy produced a striking increase in the low-frequency power of blood pressure and a tendency (borderline statistical significance) to reduce the mid-frequency power of blood pressure. Additional alpha-receptor blockade had no effect on any spectral power whereas additional cholinergic blockade caused a further increase in the low-frequency blood pressure power and a drastic reduction in all pulse interval powers. CONCLUSIONS: In the unanesthetized SHR, sympathetic activity opposes low-frequency and marginally promotes mid-frequency blood pressure fluctuations; the pulse interval spectral expression of vagal effects is spread throughout the range of frequencies explored and is not confined to the high-frequency band. These data indicate that in SHR no spectral power can specifically reflect the effects of either autonomic limb.

Adrenergic Fibers↗
PubMed1995

Reproducibility of ultrasound assessment of common carotid and femoral artery compliance and distensibility in the anesthetized rat.

OBJECTIVE: To validate ultrasound assessment of common carotid and femoral artery compliance and distensibility in the anesthetized rat. MATERIALS AND METHODS: A reproducibility study was performed by taking measurements twice on two different days in anesthetized Wistar-Kyoto (WKY) rats. The common carotid or femoral arterial diameter on one side and the contralateral arterial blood pressure were measured using a 10-MHz probe echo-Doppler device and an arterial catheter, respectively. The pressure and diameter data were stored in a computer programmed to calculate the arterial compliance and distensibility coefficients (Reneman formulas) and compliance and distensibility indices (arctangent model of Langewouters). A second experimental session was repeated 1 day later, and mean values, day-to-day mean differences and repeatability coefficients were calculated for each parameter. RESULTS: For both the common carotid and the femoral artery, the mean values for heart rate, mean arterial pressure, arterial diameter, arterial compliance and arterial distensibility were similar on the first and second days; mean day-to-day differences were small and repeatability coefficients were in the range 5-10% of the mean value for diameter and mean arterial pressure and 10-20% of the mean value for compliance and distensibility. CONCLUSIONS: In the anesthetized rat, ultrasound evaluation of the mechanical properties of the common carotid and femoral arteries is a reliable and reproducible technique.

Anesthesia, General↗