PubMed Health⌕ Search

Biomedical subjects

F Bellavere

Publications and source records attributed to F Bellavere.

At least 19 recordsLinked to original sources
PubMed2000

Power spectral analysis of heart rate in hypothyroidism.

OBJECTIVE: The aim of the present study was to evaluate the impact of hypothyroidism on the autonomic regulation of the cardiovascular system by analysing separately sympathetic and parasympathetic influences on the heart. DESIGN: In seven newly diagnosed untreated hypothyroid patients we analysed power spectral density of heart rate cyclic variations at rest, while lying, and while standing. The same protocol was repeated after the induction of stable euthyroidism by levothyroxine (L-T(4)) treatment. The results were also compared with those obtained from seven age-, sex- and body mass index-matched control subjects. METHODS: Heart rate variability was evaluated by autoregressive power spectral analysis (PSA). This method allows reliable quantification of low frequency (LF) and high frequency (HF) components of the heart rate power spectral density. These are considered to be under mainly sympathetic and purely parasympathetic control respectively. In addition, heart rate variations during deep breathing, lying to standing, and Valsalva's manoeuvre were assessed. RESULTS: PSA showed a sharp reduction in the HF (parasympathetic) component in hypothyroid subjects compared with controls (lying, 29.4+/-5.4 vs 47.7+/-6.3 normalized units (NU) (means +/- s.e.m.), P<0.05; standing, 14.0+/-3.5 vs 32.1+/-3.6NU, P<0.005). Conversely, the LF (mainly sympathetic) component was higher in hypothyroid subjects than in controls (lying, 61.6+/-6.4 vs 45.4+/-6.7 NU; standing, 71.7+/-8.0 vs 53.1+/-5.6NU), this difference being significant in the standing position. Hence, the LF/HF ratio, which is considered an index of sympathovagal balance, was increased in hypothyroid subjects while both lying (2.75+/-0.6 vs 1.16+/-0.3; P<0.05) and standing (10.0+/-3.7 vs 1.85+/-0.3; P<0. 02). Total heart rate variability, expressed as total power spectral density, was lower in hypothyroid patients than in control subjects, this difference being significant in the lying position (574+/-126 vs 2302+/-994ms(2), P<0.05). In patients re-examined after L-T(4) therapy, complete normalization of cardiovascular parameters was observed (LF/HF ratio, lying, 1.26+/-0.4; standing, 2.56+/-0.8, both P<0.01 vs baseline values). The response to conventional cardiovascular autonomic tests was not significantly different between hypothyroid patients and healthy controls, and did not change in patients after therapy. CONCLUSIONS: These results suggest that, contrary to the clinical picture, thyroid hormone deficiency is associated with an increased sympathetic influence on the autonomic cardiovascular system. The changes in sympathetic function could be explained by a secondary adaptation to an altered cardiovascular responsiveness.

Electrocardiography↗
PubMed1997

Comparative assessment of peripheral sympathetic function by postural vasoconstriction arteriolar reflex and sympathetic skin response in NIDDM patients.

PURPOSE: The aim of the study was to compare peripheral sympathetic adrenergic and cholinergic nerve function in NIDDM (non-insulin-dependent diabetes mellitus) patients with various degrees of diabetic neuropathy and neuropathic foot ulceration. The parameters used were postural vasoconstriction arteriolar reflex (VAR) and sympathetic skin response (SSR), respectively. PATIENTS AND METHODS: Forty-seven NIDDM patients were studied. No patients had clinically significant peripheral vascular disease. They were divided according to peripheral somatic neuropathy, assessed by clinical score and vibration perception threshold (VPT). Twenty-two patients showed no significant evidence of peripheral neuropathy and normal VPT (DN-); 15 had signs and symptoms of neuropathy and VPT alteration (DN+); 10 had diabetic neuropathy and foot ulceration (DNU). Twenty-two normal subjects were also examined as a control group. Resting arteriovenous shunt skin blood flow, measured using laser-Doppler flowmetry, and the VAR of the big toe on lowering the foot were studied. Sympathetic skin response was assessed by an EMG apparatus. Autonomic function was also investigated by using standard cardiovascular reflex tests. RESULTS: Resting blood flow values were similar in the three NIDDM groups and in the control group. VAR to foot lowering was significantly impaired in all NIDDM groups by comparison with controls (72.8 +/- 2.1%, mean +/- SEM), this impairment being progressively more pronounced in DN- (58.8 +/- 2.3%, P < 0.001), DN+ (33.3 +/- 3.0%, P < 0.001 versus DN-) and DNU (8.6 +/- 2.7%, P < 0.001 versus DN+). Sympathetic skin response was assessed in 28 patients and was significantly impaired in DN-compared with the control group (2.53 +/- 0.04 versus 2.71 +/- 0.04 log mcV, P < 0.01). This impairment was severe in the DNU compared with the DN+ group (1.36 +/- 0.05 versus 2.26 +/- 0.04 log mcV, P < 0.005). A positive correlation was found between VAR values and SSR (P < 0.001), and these measurements were also closely correlated with several parameters of central autonomic and somatic neuropathy. CONCLUSION: These results indicate that peripheral sympathetic adrenergic and cholinergic fibers simultaneously undergo early alterations in diabetic patients, even when there is no clinical neuropathy. Our data also show almost complete abolition of peripheral sympathetic activity in NIDDM patients with foot ulceration.

Blood Flow Velocity↗
PubMed1996

Acute effect of insulin on autonomic regulation of the cardiovascular system: a study by heart rate spectral analysis.

Insulin is suggested to have direct effects on the cardiovascular system but these are not well described. We assessed the possible influence of insulin on autonomic control of heart function. A 2-h hyperinsulinaemic euglycaemic clamp was performed in 10 healthy women (mean age 21.7 +/- 1.3 years), at two different insulin infusion rates: 80 mU m-2 and 400 mU m-2 min-1, in 7 and 3 subjects, respectively. Saline alone was infused in 4 controls. Power spectral analysis (PSA) of heart rate was recorded before and after 90-120 min of insulin infusion, as were blood pressure and heart rate. Although there were no significant changes in heart rate or blood pressure, PSA showed marked reductions of high frequency (HF) bands after insulin (2.60 +/- 0.12 vs 2.09 +/- 0.16 log ms2, p < 0.005), as at both low and high infusion rates (2.46 +/- 0.13 to 2.14 +/- 0.23 log ms2, p < 0.05, and 2.92 +/- 0.18 to 1.98 +/- 0.06 log ms2, p < 0.01, respectively). There were no significant changes of low frequency (LF) bands. Densities at LF and HF did not change significantly in control studies. As HF and LF are considered to reflect parasympathetic and mainly sympathetic control respectively, our observation of an increased LF/HF ratio (0.13 +/- 0.10 vs 0.63 +/- 0.13, p < 0.005) may be considered an index of relative sympathetic predominance induced by insulin infusion. We conclude that insulin affects the cardiovascular system, reducing vagal influence on the heart and inducing a relative hypersympathetic tone.

Adult↗
PubMed1996

Power spectral analysis of heart rate in hyperthyroidism.

The aim of the present study was to evaluate the impact of hyperthyroidism on the cardiovascular system by separately analyzing the sympathetic and parasympathetic influences on heart rate. Heart rate variability was evaluated by autoregressive power spectral analysis. This method allows a reliable quantification of the low frequency (LF) and high frequency (HF) components of the heart rate power spectral density; these are considered to be under mainly sympathetic and pure parasympathetic control, respectively. In 10 newly diagnosed untreated hyperthyroid patients with Graves' disease, we analyzed power spectral density of heart rate cyclic variations at rest, while lying, and while standing. In addition, heart rate variations during deep breathing, lying and standing, and Valsalva's maneuver were analyzed. The results were compared to those obtained from 10 age-, sex-, and body mass index-matched control subjects. In 8 hyperthyroid patients, the same evaluation was repeated after the induction of stable euthyroidism by methimazole. Heart rate power spectral analysis showed a sharp reduction of HF components in hyperthyroid subjects compared to controls [lying, 13.3 +/- 4.1 vs. 32.0 +/- 5.6 normalized units (NU; P < 0.01); standing, 6.0 +/- 2.7 vs. 15.0 +/- 4.0 NU (P < 0.01); mean +/- SEM]. On the other hand components were comparable in the 2 groups (lying, 64.0 +/- 6.9 vs. 62.0 +/- 6.5 NU; standing, 77.0 +/- 6.5 vs. 78.0 +/- 5.4 NU). Hence, the LF/HF ratio, which is considered an index of sympathovagal balance, was increased in hyperthyroid subjects while both lying (11.3 +/- 4.5 vs. 3.5 +/- 1.1; P < 0.05) and standing (54.0 +/- 12.6 vs. 9.8 +/- 2.6; P < 0.02). This parameter was positively correlated with both T3 (r = 0.61; P < 0.05) and free T4 (r = 0.63; P < 0.05) serum levels. Among traditional cardiovascular autonomic tests, the reflex response of heart rate during lying to standing was significantly lower in hyperthyroid patients than in controls (1.12 +/- 0.03 vs. 1.31 +/- 0.04; P < 0.002). No statistically significant difference in reflex responses between the two groups was found in deep breathing or Valsalva's maneuver. In the 8 patients reexamined after methimazole treatment, we observed complete normalization of altered cardiovascular parameters, with slight predominance of the vagal component compared with controls. These results suggest that thyroid hormone excess may determine reduced parasympathetic activity and, thus, a relative hypersympathetic tone.

Adolescent↗
PubMed1992

Power spectral analysis of heart-rate variations improves assessment of diabetic cardiac autonomic neuropathy.

Power spectral analysis (PSA) of heart-rate variations has recently proved a useful tool in evaluating cardiovascular autonomic activity. It offers the possibility of examining both the functioning of parasympathetic and sympathetic pathways through breakdown into two frequency bands, and of their effects on heart-rate cyclic variability. We applied an autoregressive model for PSA to study overall autonomic tone in 20 male age-matched control subjects and 53 insulin-dependent (type I) diabetic subjects, subdivided into three groups of 20, 15, and 18, each group presenting different degrees of autonomic involvement. We found that: 1) power spectrum density (PSD) values at high-frequency bands (parasympathetic dependent) were similar in diabetic subjects without cardiac autonomic neuropathy (CAN) and in control subjects, but differed significantly from diabetic subjects with mild CAN and severe CAN, both standing and lying; 2) PSD values at low frequency (mainly sympathetic dependent) were similar, or slightly different, in diabetic subjects without CAN and in control subjects, but differed significantly from diabetic subjects with mild and severe CAN, both standing and lying; 3) as an expression of parasympathetic versus sympathetic coherence, correlations, both standing and lying, existed between PSD values at low- and high-frequency bands in control and diabetic subjects without CAN, but not in diabetic subjects with CAN; and 4) different degrees of correlation characterized the PSD values of high and low frequencies versus traditional cardiovascular test values in the diabetic subjects. The best correlation was between PSD low-frequency values and the lying-to-standing maneuver.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Heart rate spectral analysis for assessing autonomic regulation in diabetic patients.

Spectral analysis of the R-R variability signal has been used for assessing the autonomic regulation of heart rate in control subjects and in diabetic patients affected by autonomic neuropathy. Modifications of the parasympathetic-sympathetic balance following postural changes, as observed in normal subjects, were not significant in autonomic patients. In addition, the overall reduction of power occurring in diabetics at all frequencies indicates the impairment of both autonomic components.

Diabetes Mellitus↗
PubMed1988

Prolonged QT period in diabetic autonomic neuropathy: a possible role in sudden cardiac death?

Twenty four men with insulin dependent diabetes and different degrees of autonomic neuropathy were studied to establish the response of the QT interval to various heart rates. Nine men with autonomic neuropathy had a longer QT interval than 13 healthy individuals and 15 patients who had diabetes without, or with only mild, autonomic neuropathy. Those with autonomic neuropathy also had a proportionally greater lengthening of the QT interval for a given increase in RR interval. The results of this study suggest a basis for the finding that sudden death is more common in patients with diabetic autonomic neuropathy.

Adult↗
PubMed1987

Autonomic mechanisms in the heart rate response to coughing.

To differentiate between the possible reflex and mechanical components in the heart rate response to cough, eight healthy subjects performed a standardized cough test before and after pharmacological autonomic blockade; to test the clinical usefulness of the cough manoeuvre two groups of diabetic patients (without and with autonomic neuropathy) were compared with a group of age-matched normal subjects. Because of the use of abdominal and expiratory muscles during cough, the cardioacceleratory response was compared with that induced by an intense contraction of the arm muscles (handgrip). The cardioacceleratory response was completely abolished by atropine while propranolol failed to affect it. The diabetic patients with autonomic neuropathy showed a response similar to that after cholinergic blockade. The response was similar to that induced by muscular contraction for 4 s, after which it differed showing a continued cardioacceleration. The patterns of recovery were not different. The cough-induced cardioacceleration is essentially reflex in nature and under cholinergic control; initially the mechanism may be partially related to the intense contraction of abdominal and expiratory muscles; later, the arterial hypotension related to the cough may contribute to the more sustained shortening of the R-R interval. The cough test may be useful for the evaluation of cardiac parasympathetic integrity.

Adult↗
PubMed1986

Correlation of cardiovascular and neuroendocrine tests of autonomic function in diabetes.

Six normal subjects and 16 insulin-dependent diabetics with varying degrees of autonomic damage each had blood sampled for norepinephrine and pancreatic polypeptide for fifteen minutes after a mixed meal and intravenous (IV) edrophonium (Tensilon). The normal subjects showed a brisk but short-lived rise in norepinephrine after edrophonium (average maximum increase 70% between 2 and 6 minutes), as did most diabetics. However, diabetics with cardiovascular reflex evidence of sympathetic damage showed no rise in norepinephrine. Pancreatic polypeptide concentrations increased up to 400% above baseline after a mixed meal in both the normal and the diabetic group with normal cardiovascular reflexes. There was no significant rise in pancreatic polypeptide either in the diabetics with parasympathetic damage alone or in those with additional sympathetic damage. These results provide further evidence for the diffuse nature of the damage in diabetic autonomic neuropathy.

Adult↗
PubMed1986

[Correlation between QT interval, ventricular arrhythmias and left ventricular function in chronic alcoholics].

Prolonged QT interval and arrhythmias have been reported to occur in chronic alcoholics. To investigate the role of chronic alcohol consumption in the onset of arrhythmias and the development of the preclinical left ventricular dysfunction, in a group of 12 asymptomatic chronic alcoholics with no clinical evidence of heart disease, with histologically proven hepatic damage, after a week of abstinence from alcohol, the following investigations were performed: measurements of the corrected QT interval (QTc), 24-hours Holter monitoring, systolic time intervals, M-mode echocardiograms. The results were compared to those of 10 normal subjects. Our data suggested no difference in QTc interval between chronic alcoholics and normal persons. The distribution of arrhythmias was not statistically different in the two groups, particularly frequent and complicated arrhythmias occurred in only one subject in each group. Preejection period corrected for heart rate (PEPI) was significantly longer in alcoholics (132 +/- 16 vs 119 +/- 11, p less than 0.05). All echocardiographic parameters examined were not significantly different in the two groups. On the basis of our results, our impression is that the arrhythmogenic role of alcohol, not under acute ingestion, is relatively unimportant and further studies are needed to become a definitive conclusion about subclinical alcoholic cardiomyopathy.

Adult↗
PubMed1985

Improvement of cardiovascular autonomic reflexes after amelioration of metabolic control in insulin-dependent diabetic subjects with severe autonomic neuropathy.

To evaluate the influence of good metabolic equilibrium on Diabetic Autonomic Neuropathy (DAN), cardiovascular autonomic reflexes were monitored in 9 male insulin-dependent diabetic patients with DAN, treated with Continuous Subcutaneous Insulin Infusion (CSII) by pump: 9 for 10 days, 4 for 1 year and 2 for 20 months. Autonomic neuropathy was assessed evaluating 5 cardiovascular autonomic tests: Valsalva Manoeuvre (VR), Deep Breathing (DB), Lying-to-Standing (L-S), Sustained Handgrip (SHG), and Postural Hypotension (PH). Metabolic control was assessed evaluating the mean daily plasma glucose, glucosuria and glycosylated hemoglobin. Ten days of CSII treatment induced a normalization of glucose balance and a slight but significant improvement in some parasympathetic cardiovascular tests (VR: from 1.09 +/- 0.01 to 1.13 +/- 0.02; P less than 0.05). After 4-8 months of CSII treatment a significant improvement in VR (P less than 0.05); DB (P less than 0.01) and L-S (P less than 0.05) was recorded. The long-term treatment with CSII did not seem to induce a further amelioration in cardiovascular autonomic reflexes. These results show that the slight improvement induced by good metabolic balance in the cardiovascular autonomic response could be related to functional-metabolic rather than structural changes in the nerves.

Adult↗
PubMed1985

Evidence of early impairment of parasympathetic reflexes in insulin dependent diabetics without autonomic symptoms.

Cardiovascular (CV) autonomic functions were assessed in 50 insulin-dependent diabetic patients and in 30 controls using a battery of autonomic tests: Valsalva Manoeuvre (VR), Deep Breathing (DB), Lying-to-Standing (LS), Sustained Handgrip (SHG) and Postural Hypotension (PH). The results were compared with those obtained from a study of cardiac resting adjustment to different static postures (quiet lying and standing). 10 diabetics with abnormal responses to the majority of tests were considered affected by Diabetic Autonomic Neuropathy (DAN); 15 with some abnormal of borderline responses were defined much less than Borderlines much greater than. The remaining 25 diabetics, while displaying lower values than the controls in parasympathetic tests, had much less than normal much greater than autonomic responses. The VR mean (+/- SD) value was 1.71 +/- 31 in much less than normal much greater than diabetics and 2.01 +/- 0.29 in controls (p less than 0.001); the DB mean value was 20.6 +/- 87 and 28 +/- 8.13 (p less than 0.001), and the LS mean value 1.16 +/- 0.12 and 1.33 +/- 0.18 (p less than 0.001) respectively. No significant differences were found in the sympathetic tests (SHG, PH). However Heart Rate (HR) adjustment of diabetics with normal CV responses to immobile standing (RR mean 783 +/- 136 ms) and lying (RR mean increment of 25 +/- 11%; p less than 0.001) was similar to that of controls who had a resting HR standing (RR mean 749 +/- 104 ms) and lying (RR mean 884 +/- 116 ms) with a mean increment of 20.2 +/- 10.9% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Influence of continuous subcutaneous insulin infusion (CSII) treatment on diabetic somatic and autonomic neuropathy.

Near-normal plasma daily glucose profile was induced by Continuous Subcutaneous Insulin Infusion (CSII) treatment in order to evaluate its influence on diabetic somatic and autonomic neuropathy. Twelve insulin-dependent diabetic subjects with somatic neuropathy were studied before and after a short term CSII treatment of 10 days. Four out of these subjects, all affected by autonomic neuropathy, were followed for 1 yr with controls every four months. Metabolic equilibrium was monitored by mean daily plasma glucose (MPDG) profile and by Glycosylated Hemoglobin (GHb) evaluation. Somatic neuropathy was studied assessing conduction velocity at peroneal motor (PMCV) nerve, ulnar motor (UMCV), ulnar sensory (USCV) and sural sensory (SSCV) nerves. Autonomic neuropathy was assessed by means of a battery of five cardiovascular autonomic tests: Valsalva Manoeuvre (VR), Deep Breathing (DB), Lying-to-Standing (LS), Sustained HandGrip (SHG) and Postural Hypotension (PH). Short-term CSII treatment induced a near normalization of metabolic parameters, a significant improvement in VR (p less than 0.05) and DB (p less than 0.01) values, but no changes in NCV. The prolongation of CSII treatment in 4 subjects induced a significant (p less than 0.05) improvement in VR, DB and LS values and in PMCV and UMCV after 4 months. This improvement did not increase with the longer CSII treatment (1 yr).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Impairment of cardiovascular autonomic reflexes in multiple symmetric lipomatosis.

Cardiovascular autonomic reflexes were evaluated in 13 male subjects affected by Multiple Symmetric Lipomatosis (MSL) and the results were compared with those obtained in 13 age-matched male controls and in 16 male heavy drinkers matched with the MSL group for age and alcohol intake. Valsalva Manoeuvre (VR), Heart Rate variations on Deep Breathing (DB) and R-R intervals 30/15 ratio during Lying-to-Standing (LS) (tilting), were used as primarily parasympathetic tests. As primarily sympathetic tests, we assessed the increment of diastolic blood pressure in Sustained Handgrip (SHG) and the fall of systolic blood pressure on standing (Postural Hypotension = PH). Mean values of VR and DB were significantly (P less than 0.001) lower in MSL subjects than in controls and heavy drinkers. Mean LS values were significantly lower in MSL subjects (P less than 0.001) and in heavy drinkers (P less than 0.01) in relation to controls. No significant differences were observed in the 3 groups of subjects regarding the mean values of PH and SHG. The results suggest that MSL is characterized by an impairment of autonomic function. This impairment seems to be prevalently parasympathetic and not related to a high alcohol intake.

Adult↗
PubMed1984

Impaired auditory brainstem-evoked responses in insulin-dependent diabetic subjects.

Auditory brainstem-evoked responses (ABR) were recorded from the scalp of 30 normoacoustic insulin-dependent diabetic subjects, aged between 15 and 41 yr (29 +/- 7 yr). Three different stimulus repetition rates (11, 37, and 87 cps) were used. The results were compared with those obtained from 20 age- and sex-matched, normoacoustic control subjects. In diabetic patients, metabolic control (mean daily plasma glucose, glycosylated hemoglobin) and the presence of retinopathy, nephropathy, and somatic neuropathy were also investigated. The latencies (ms) of ABR waves were significantly impaired in diabetic subjects as compared with normals. Peripheral transmission time (wave I) and central transmission time (waves I-V) were also significantly delayed in diabetic subjects. Moreover, by increasing stimulus repetition rates, a significant increase in waves I-V shift was observed in diabetic patients. ABR impairment was not related to glucose balance, to the duration of diabetes, or to the presence of the diabetic retinopathy, nephropathy, and somatic neuropathy. In conclusion, diabetic neuropathy is characterized not only by somatic and autonomic nerve dysfunctions, but also by the early involvement of the central nervous system (CNS). ABR recording can represent a useful, noninvasive, simple procedure to detect both acoustic nerve and CNS damage.

Adolescent↗
PubMed1983

Abnormalities of ambulatory 24-hour heart rate in diabetes mellitus.

Twenty-one normal subjects and 64 diabetics with varying severity of autonomic damage underwent 24-h ambulatory EKG monitoring. No diabetics had the "sick sinus syndrome," and the frequency of arrhythmias was no higher than in the normal subjects. The diabetics had higher mean hourly heart rates, and with increasing autonomic damage there was reduction in diurnal heart rate variation. The mean waking and sleeping heart rates were higher in the diabetics. The maximum heart rates were not significantly different, but the minimum heart rates were significantly higher in the diabetics. These previously unrecognized abnormal 24-h heart rate patterns provide further evidence of damage to the heart rate-controlling mechanisms in diabetes mellitus.

Adult↗