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S Guzzetti

Publications and source records attributed to S Guzzetti.

At least 37 records · Page 2Linked to original sources
PubMed1994

Altered dynamics of the circadian relationship between systemic arterial pressure and cardiac sympathetic drive early on in mild hypertension.

1. This study was designed to test the hypothesis that simultaneous non-invasive assessment of the circadian variations in both intermittent arterial pressure and the continuous 24 h changes of spectral markers of cardiac neural control could provide new information on cardiovascular regulatory mechanisms, in hypertensive patients and normotensive subjects. To test this hypothesis we studied 18 subjects with mild hypertension and 11 normotensive subjects in whom we recorded simultaneously non-invasive intermittent arterial pressure and Holter electrocardiogram for 24 h. We also studied the same subjects during resting and standing conditions in the clinical laboratory. 2. The normalized power of the low-frequency (approximately 0.1 Hz) spectral component of R-R interval variability, considered mainly a marker of sympathetic drive to the sino-atrial node, was, at rest, significantly higher in the hypertensive than in the normotensive subjects, as already reported. Moreover, the values of the low-frequency component at rest recorded in the clinical laboratory were significantly correlated with those obtained from ambulatory recording during night rest. The decrease in the values of arterial pressure during the night-time was accompanied by a reduction in the power of the low-frequency component only in the case of normotensive subjects. Accordingly, the slope of the regression of the low-frequency component as a function of systolic arterial pressure during ambulatory recordings was steep in normotensive subjects and flat in hypertensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Morning and Monday: critical periods for the onset of acute myocardial infarction. The GISSI 2 Study experience.

The onset of acute myocardial infarction (AMI) is unevenly distributed over the 24 h and the week. While presence of a morning peak is generally agreed upon, contrasting results had been obtained regarding other periods of the day, probably due to differences of origin, size and composition of the populations. The 24 h and weekly distributions were studied within 6 h from the beginning of the symptoms in a population following a Latin life-style, who were enrolled in the GISSI 2 Study (n = 11472). Subgroups (smokers, the elderly (> 65 years), diabetics, hypertensives) were also considered. Six hour periods starting at midnight were tested for uniformity. Circadian non-uniformity was found. Events increased in the morning hours and reduced during the night regardless of the day of the week. The night and day difference was attenuated in smokers and diabetics. Non-uniformity of the events was also found among the days of the week. AMI significantly increased in non-smokers on Monday. We suggest that there is a night-day gradient (characterized by the short time interval between the two frequency extremes) in the time of onset of AMI. The different distribution in smokers stresses the possible unfavourable and masking effect of a heightened sympathetic tone during the day while the general protective role of the night hours is preserved. Moreover, the increased incidence of events on Monday may suggest the importance of the shift from a period of non-scheduled to scheduled activity.

Aged↗
PubMed1994

Influences of neural mechanisms on heart period and arterial pressure variabilities in quadriplegic patients.

The heart period (R-R) variability power spectrum presents two components, at low (LF; approximately 0.10 Hz) and high (approximately 0.25 Hz) frequencies, whose reciprocal powers appear to furnish an index of sympathovagal interaction modulating heart rate. In addition, the LF component of the systolic arterial pressure variability spectrum furnishes a marker of sympathetic modulation of vasomotor activity. The contribution of spinal and supraspinal neural circuits to the genesis of these rhythmic oscillatory components remains largely unsettled. Therefore we performed spectral analysis of R-R and systolic arterial pressure variabilities in 15 chronic neurologically complete quadriplegic patients (QP) and in 15 control subjects during resting conditions, controlled respiration, and head-up tilt. At rest, in seven QP the LF component was undetectable in both cardiovascular variability spectra; in two QP this component was present only in R-R variability spectrum, whereas the remaining six showed a significantly reduced LF in both signals. In QP, the LF component, when present, underwent paradoxical changes with respect to controls, decreasing during tilt and increasing during controlled respiration. In five QP in whom the recording session was repeated after 6 mo, a significant increase in LF was observed in both variability spectra. These data confirm the finding that a disconnection of sympathetic outflow from supraspinal centers can cause the disappearance of the LF spectral component. However, LF presence in some QP supports the hypothesis of a spinal rhythmicity likely to be modulated by the afferent sympathetic activity.

Adolescent↗
PubMed1994

[Asymptomatic hyperparathyroidism. Influence of PTH values on the therapeutic decision].

The majority of patients affected by primary hyperparathyroidism present now in surgical series are little or totally asymptomatic. This is due to widespread use of multiphasic screening for hypercalcemia as far as to more liberal indications for parathyroid exploration. The debate about the need for parathyroidectomy is open in these patients, having few or no signs at all of primary hyperparathyroidism, because conservative treatment has yielded confused results. The authors analyzed preoperative biochemical values and surgical outcome from 26 patients affected by primary hyperparathyroidism. Thirteen cases had overt primary hyperparathyroidism (group A) and 13 had asymptomatic disease (group B). Patients in group A had higher preoperative PTH values than patients in group (p < 0.05). After surgery, the patients in group A showed parathyroid glands which weighted significatively more than ones in group B (p +/- 0.01). Further, a significant correlation between preoperative PTH value and glandular weight was demonstrated in all cases. The authors conclude surgery for patients having mild primary hyperparathyroidism may give some problems related to the very small size of abnormal glands found during operation. We advise a close follow-up for these patients initially without treatment: surgery should be recommended for those showing PTH values higher than 150 pg/ml.

Adult↗
PubMed1994

Non-linear dynamics of cardiovascular variability signals.

Long-term regulation of beat-to-beat variability involves several different kinds of controls. A linear approach performed by parametric models enhances the short-term regulation of the autonomic nervous system. Some non-linear long-term regulation can be assessed by the chaotic deterministic approach applied to the beat-to-beat variability of the discrete RR-interval series, extracted from the ECG. For chaotic deterministic systems, trajectories of the state vector describe a strange attractor characterized by a fractal of dimension D. Signals are supposed to be generated by a deterministic and finite dimensional but non-linear dynamic system with trajectories in a multi-dimensional space-state. We estimated the fractal dimension through the Grassberger and Procaccia algorithm and Self-Similarity approaches of the 24-h heart-rate variability (HRV) signal in different physiological and pathological conditions such as severe heat failure, or after heart transplantation. State-space representations through Return Maps are also obtained. Differences between physiological and pathological cases have been assessed and generally a decrease in the system complexity is correlated to pathological conditions.

Algorithms↗
PubMed1992

Circadian variation of spectral indices of heart rate variability after myocardial infarction.

The circadian variations of spectral indices of heart rate variability were analyzed in 20 patients 4 weeks after a first and uncomplicated myocardial infarction (MI) and in 20 control subjects. R-R interval and variance showed a characteristic day-night pattern with a significant reduction of the latter parameter in patients after MI (10,967 +/- 1109 msec2 vs 16,860 +/- 2132 msec2). Control subjects were characterized by a predominance of low-frequency (approximately 0.1 Hz) component during the day and of high-frequency (approximately 0.25 Hz) component during the night, which reflected the expected 24-hour pattern of variation of sympatho-vagal balance. A 24-hour elevation (64 +/- 3 normalized units [nu] vs 56 +/- 2 nu; p less than 0.05) of the low-frequency component and a smaller (23 +/- 2 nu vs 32 +/- 2 nu; p less than 0.05) high-frequency component during the night differentiated patients after MI from subjects. The difference between the two groups was even more evident when the 24-hour sympatho-vagal balance was assessed with the low frequency/high frequency ratio. Thus spectral analysis of heart rate variability indicates that in patients after MI there is an alteration of neural control mechanisms as indicated by the presence of signs of sympathetic activation and by the attenuation of the nocturnal increase in vagal tone.

Aged↗
PubMed1992

AIDS-defining diseases in 250 HIV-infected patients; a comparative study of clinical and autopsy diagnoses.

OBJECTIVE: To evaluate the correlation between clinical and autopsy findings in 250 AIDS patients. METHODS: Clinical and autopsy diagnoses of AIDS-defining diseases in 250 AIDS patients who died in Milan between May 1984 and February 1991 were compared. RESULTS: Pneumocystis carinii (PCP) and oesophageal candidiasis were the most frequent clinical diagnoses, while cytomegalovirus (CMV) infection was observed in almost half of the autopsies. Forty-seven per cent of the diseases found at autopsy had not been diagnosed during life; CMV infection, mycoses, HIV-specific brain lesions, cerebral lymphomas and progressive multifocal leukoencephalopathy (PML) had a higher rate of non-diagnosis in life. CMV visceral infection accounted for the majority of the diseases not recognized in life. In contrast, clinically diagnosed PCP, oesophageal candidiasis and, to a lesser degree, brain toxoplasmosis were often not found at autopsy, possibly indicating a significant rate of recovery and prevention of relapse. Finally, bacterial pneumonia and sepsis, although not AIDS indicator diseases, were observed in approximately one-third of the autopsies. CONCLUSION: Considerable differences in the frequency and type of the AIDS-defining diseases diagnosed during life and at post mortem were found.

AIDS-Related Opportunistic Infections↗
PubMed1991

Impaired heart rate variability in patients with chronic Chagas' disease.

Spectral analysis of heart rate variability was used to investigate the possible alteration in sympathovagal control of heart rate in patients with Chagas' disease. The study included 31 subjects, divided into three groups: controls, Chagas' 1 (subjects with only positive serology for Chagas' disease) and Chagas' 2 (subjects with positive serology and electrocardiographic abnormalities that are usually found in this disease). The subjects were studied during rest, while standing, and during handgrip exercise. With this approach, the low frequency (approximately 0.1 Hz) spectral component of R-R interval variability is considered to be a marker primarily of sympathetic activity, whereas the high frequency (approximately 0.25 Hz) component, which is related to respiration, seems mainly to reflect vagal activity. We observed significant (p less than 0.05) differences among the three groups during standing: although in the control subjects the low-frequency component increased (delta = 30 +/- 5 normalized units, nu), there was no increase in Chagas' 1 (delta = -1 +/- 8 nu) and Chagas' 2 (delta = -2 +/- 8 nu) patients. During handgrip exercise, another test that is capable of exciting sympathetic outflow, there was an increase of low frequency only in control subjects. These results confirm the occurrence of quantitative and assessable abnormalities in the neural control of heart rate variability in Argentinian patients with chronic Chagas' disease, even in the absence of heart failure.

Chagas Disease↗
PubMed1991

Altered pattern of circadian neural control of heart period in mild hypertension.

We addressed the problem of the circadian changes in neural control of heart period in ambulant hypertensive subjects. A running spectral analysis of R-R variability from Holter tapes provided markers of sympathetic, i.e. low-frequency component (LF) almost equal to 0.10 Hz, and vagal, i.e. high-frequency component (HF) almost equal to 0.25 Hz, controlling activities for the 24-h period of the recording. Significant circadian differences were observed in LF between the two groups of subjects: during night-time rest (0300-0400 h), LF was greater in hypertensives than in normotensives (56 +/- 2 and 48 +/- 2 nu, respectively; P less than 0.05). Furthermore, the difference between daytime and night-time LF values was progressively reduced with increasing severity of the hypertensive state, as assessed by resting arterial pressure levels. Spectral analysis of R-R variability suggests that essential hypertension may be characterized by a reduced day-night oscillation in sympathetic activity than can be quantified non-invasively using this approach.

Adult↗
PubMed1990

Effects of sympathetic activation on heart rate variability in Chagas' patients.

To assess the alterations present in neural control of heart rate in patients with signs of Chagas' disease we studied the spectral components of heart rate variability in 10 Chagas' patients, without cardiac failure, and in 10 control subjects during supine and standing position. Chagas' patients during standing did not present the changes in the spectral components of heart rate variability which normally accompany sympathetic activation and vagal withdrawal.

Arrhythmias, Cardiac↗
PubMed1990

Continuous 24-hour assessment of the neural regulation of systemic arterial pressure and RR variabilities in ambulant subjects.

In this study, we tested the hypothesis that the neural control of circulation in humans undergoes continuous but in part predictable changes throughout the day and night. Dynamic 24-hour recordings were obtained in two groups of ambulant subjects. In 18 hospitalized patients free to move, direct high-fidelity arterial pressures and electrocardiograms were recorded, and in an additional 28 nonhospitalized subjects, only electrocardiograms were obtained. Spectral analysis of systolic arterial pressure and of RR interval variabilities provided quantitative markers of sympathetic and vagal control of the sinus node and of sympathetic modulation of vasomotor tone. With this approach, the low-frequency (approximately 0.1 Hz) component of RR interval and systolic arterial pressure variabilities is considered a marker primarily of sympathetic activity, whereas the high-frequency (approximately 0.25 Hz) component of RR interval variability, related to respiration, seems to be a marker primarily of vagal activity. We observed a pronounced and consistent reduction in the markers of sympathetic activity and an increase in those of vagal activity during the night. In the invasive studies, while the subjects were still lying in bed after waking up, the markers of sympathetic activity rose rapidly and concomitantly with a simultaneous vagal withdrawal. Noninvasive studies confirmed the early morning rise of the markers of sympathetic activity and the circadian pattern of sympathovagal balance. These data indicate that the ominously increased rate of cardiovascular events in the morning hours may reflect the sudden rise of sympathetic activity and the reduction of vagal tone.

Blood Pressure↗
PubMed1989

Compressed spectral arrays for the analysis of 24-hr heart rate variability signal: enhancement of parameters and data reduction.

Heart rate variability signal in the form of an R-R interval tachogram is detected in Holter type 24-hr ECG recordings. Spectral analysis is carried out over consecutive nonoverlapping records, and the information is displayed in the form of a compressed spectral array through parametric techniques. The trends of spectral parameters such as low-frequency (LF) and high-frequency (HF) powers and central frequencies are also plotted, together with the classical mean R-R value and variance relative to each single spectrum. These parameters quantify the effect of sympatho-vagal balance on heart rate control during the 24-hr period and provide important elements for the diagnostic evaluation of various pathologies, like hypertension. A spectral compression algorithm which checks the position of the poles relative to LF and HF bands inside the unitary circle in the complex zeta-plane is also developed. Applications of this procedure are foreseen in the clinical evaluation of ambulant patients as well as in the study of physical and psychological stress.

Algorithms↗
PubMed1988

Spectral analysis of heart rate variability in the assessment of autonomic diabetic neuropathy.

We studied heart rate variability in 49 uncomplicated diabetics (27 with insulin therapy; 22 with oral hypoglycemic agents) and in 40 age-matched controls. An automatic autoregressive algorithm was used to compute the power spectral density (PSD) of beat by beat RR variability derived from the surface ECG. The PSD contains two major components (a low frequency approximately 0.1 Hz (LF) and a high frequency, respiratory linked, approximately 0.25 Hz (HF] that provide, respectively, quantitative markers of sympathetic and vagal modulatory activities and of their balance. As compared to controls, in diabetics, besides a reduced RR variance at rest (2722 +/- 300 and 1436 +/- 241 ms2, respectively), we observed during passive tilt an altered response of spectral indices of sympathetic activation and vagal withdrawal, suggestive of a complex modification in the neural control activities. In addition, we compared this approach to the commonly used clinical tests score, and observed that the latter provides overall results similar to those obtained with spectral changes induced by tilt (r = 0.42; P less than 0.01). Of potential clinical importance is that the data obtained with spectral analysis appear more thoroughly quantifiable and do not require the active collaboration of the patients.

Adolescent↗
PubMed1988

Sympathetic predominance in essential hypertension: a study employing spectral analysis of heart rate variability.

In this study on 91 subjects we tested the hypothesis of an enhanced sympathetic activity in uncomplicated essential hypertension employing spectral analysis of heart rate variability. With this technique the tonic sympathetic and vagal activities and their changes are respectively assessed by the power of approximately 0.1 Hz (low frequency, LF) and approximately 0.25 Hz (respiratory linked, high frequency, HF) components of the spectrum of the beat by beat variability of RR interval. When comparing the 40 subjects with diastolic blood pressure consistently greater than 95 mmHg (hypertensives, Ht), with 35 age-matched controls (diastolic arterial pressure less than 90 mmHg, Nt), we observed that LF was greater and HF smaller in Ht as compared to Nt, thus suggesting an enhanced sympathetic activity and a reduce vagal activity in Ht. Additionally, passive tilt, which in Nt enhances LF [delta = 26 +/- 2 normalized units (nu)] and reduces HF (delta = -22 +/- 2, nu), produced smaller (P less than 0.05) changes in Ht (delta LF = 6.3 +/- 2.7 and delta HF = -7.5 +/- 2.3 nu). Furthermore, the values of LF at rest and the altered effects of tilt on LF and HF were significantly correlated with the degree of the hypertensive state. Chronic beta-adrenergic blockade (atenolol 100 mg once daily for 2 weeks, n = 13) reduced heart rate and blood pressure (from 162/103 to 136/88 mmHg) together with a significant diminution of LF and an increase of HF. Thus, spectral analysis of RR variability appears to be a convenient non-invasive technique to follow the progressive alterations in sympatho-vagal balance present in essential hypertension.

Adult↗
PubMed1988

Cerebral complications of coronary by-pass surgery. A prospective study.

A prospective study was undertaken of cerebral complications in 91 patients undergoing coronary by-pass surgery. Patients showing clinically relevant neurological complications had longer pump-times but did not differ in pre-operative variables. Worsening of neurological state correlated with duration of pump-time but not with pre-operative variables. Duration of pump-time appears to be the main predictor of neurological complications after coronary by-pass surgery.

Adult↗