Alessandra Fiorentini

Circadian rhythm of the autonomic nervous system in insulin resistant subjects with normoglycemia, impaired fasting glycemia, impaired glucose tolerance, type 2 diabetes mellitus.

BackgroundIn type 2 diabetes mellitus both insulin resistance and hyperglycemia are considered responsible for autonomic dysfunction. The relation between the autonomic activity, impaired fasting glycemia and impaired glucose tolerance is, however, unclear. The purpose of this study was to evaluate and compare the circadian autonomic activity expressed as heart rate variability (HRV) measured by 24-hours ECG recording in insulin resistant subjects (IR) with characteristics as follow: IR subjects with normal oral glucose tolerance test results, IR subjects with impaired fasting glucose, IR subjects with impaired glucose tolerance and subjects with type 2 diabetes mellitus.MethodsEighty Caucasian insulin resistant subjects (IR) and twenty five control subjects were recruited for the study. IR subjects were divided into four groups according to the outcoming results of oral glucose tests (OGTTs): IR subjects with normal glucose regulation (NGR), IR subjects with impaired fasting glycemia (IFG), IR subjects with impaired glucose tolerance (IGT) and subjects with type 2 diabetes mellitus (DM). Autonomic nervous activity was studied by 24-hours ECG recording. Heart rate variability analysis was performed in time and frequency domains: SDNN, RMS-SD, low frequency (LF) and high frequency (HF) were calculated.ResultsThe total SDNN showed statistically significant reduction in all four groups with insulin resistant subjects (IR) when compared to the control group (p <0,001). During night LF normalized units (n.u.) were found to be higher in all four groups including IR subjects than in the control group (all p < 0,001) and subjects with normal glucose regulation (NGR), with impaired fasting glycemia (IFG) and with impaired glucose tolerance (IGT) were found to have higher LF n.u. than those in the type 2 diabetes mellitus group. The linear regression model demonstrated direct association between LF values and the homeostasis model assessment-index (HOMA-I), in the insulin resistant group (r = 0,715, p <0,0001).ConclusionThe results of our study suggest that insulin resistance might cause global autonomic dysfunction which increases along with worsening glucose metabolic impairment. The analysis of sympathetic and parasympathetic components and the sympathovagal balance demonstrated an association between insulin resistance and sympathetic over-activity, especially during night. The results indicated that the sympathetic over-activity is directly correlated to the grade of insulin resistance calculated according to the HOMA-I. Since increased sympathetic activity is related to major cardiovascular accidents, early diagnosis of all insulin resistant patients should be contemplated.

Circadian rhythm of autonomic activity in non diabetic offsprings of type 2 diabetic patients.

The aim of the present study was to evaluate, by heart rate variability (HRV) with 24-hours ECG Holter (HRV), the circadian autonomic activity in offspring of type 2 diabetic subjects and the relation with insulin-resistance. METHODS: 50 Caucasian offsprings of type 2 diabetic subjects were divided in two groups: insulin-resistant offsprings (IR) and non insulin-resistant offsprings (NIR). Autonomic nervous activity was studied by HRV. Time domain and spectral analysis (low frequency, LF, and high frequency, HF, provide markers of sympathetic and parasympathetic modulation when assessed in normalized units) were evaluated. RESULTS. Time domain showed a reduction of total SDNN in IR (p < 0.001) and NIR (p 0.047) versus controls. Spectral analysis showed a total and night LF higher in IR and NIR than in control group (all p < 0.001). CONCLUSION. In frequency domain, the analysis of sympathetic (LF) and parasympathetic (HF) component evidenced an association between the offspring of type 2 diabetic subjects and a sympathetic overactivity. A global reduction and alteration of circadian rhythm of autonomic activity are present in offspring of type 2 diabetic patients with and without insulin resistance. The data of our study suggested that an autonomic impairment is associated with the familiarity for type 2 diabetes independently to insulin resistance and that an impairment of autonomic system activity could precede the insulin resistance.

The correlation among QTc interval, hyperglycaemia and the impaired autonomic activity

BACKGROUND The QT interval reflects the duration of the intracellular action potential. Little is known on the interval QT duration in non diabetic insulin-resistant subjects. OBJECTIVE The aims of the current study were to evaluate the QTc interval in three groups of non diabetic insulin-resistant subjects and the possible correlation between QTc and the autonomic nervous systems activity. DESIGN 90 subjects were divided in subjects with impaired fasting glycaemia (IFG) and, by the results of OGTT, according to the criteria of ADA, in subjects with normal glucose regulation (NGR) and impaired glucose tolerance (IGT). Insulin resistance was evaluated by the homeostasis model assessment-index (HOMA-I). Heart rate variability and Qtc were calculated. RESULTS QTc interval is correlated with SDNN, LF n.u. and LF/HF. CONCLUSION We have observed that the QTc interval is prolonged in insulin-resistant subjects with associated impaired glucose metabolism, while no difference was reported between insulin-resistant and non insulin-resistant subjects with normal glucose regulation. We hypothesize that hyperglycaemia could play a major role than hyperinsulinemia on the QTc prolongation.

QTc interval prolongation in HIV-infected patients: a case–control study by 24-hour Holter ECG recording

BackgroundAim of the study was to assess QTc interval by a 24-hour ECG recording in a group of HIV-infected individuals with a basal prolonged QTc. The risk factors associated with QTc prolongation and the indices of cardiovascular autonomic control were also evaluated.MethodsA case–control study was performed using as cases 32 HIV-infected patients with prolonged (>440 msec) QTc interval as assessed by Holter ECG, and as controls 64 HIV-infected subjects with normal QTc interval. Autonomic function was evaluated by heart rate variability analysis during 24-hour recording.ResultsDuration of HIV disease was significantly longer among cases than among controls (p=0.04). Waist/hip ratio was also higher among cases than among controls (p=0.05). Frequency domain analysis showed the absence of physiologic decrease of low frequency (LF) in the night period in both cases and controls. The LF night in cases showed a statistically significant reduction when compared with controls (p=0.007).ConclusionsIn our study group, QTc interval prolongation was associated with a longer duration of HIV infection and with a greater waist/hip ratio. HIV patients with QTc interval prolongation and with a longer duration of HIV infection were more likely to have an impairment of parasympathetic and sympathetic cardiac component.

Autonomic system modification in Zen practitioners.

BACKGROUND Meditation in its various forms is a traditional exercise with a potential benefit on well-being and health. On a psychosomatic level these exercises seem to improve the salutogenetic potential in man.Especially the cardiorespiratory interaction seems to play an important role since most meditation techniques make use of special low frequency breathing patterns regardless of whether they result from a deliberate guidance of breathing or other mechanisms, for example, the recitation of specific verse. During the different exercises of Zen meditation the depth and the duration of each respiratory cycle is determined only by the process of breathing. Respiratory manoeuvres during Zazen meditation may produce HR variability changes similar to those produces during biofeedback. Recognition that the respiratory sinus arrhythmia (RSA) was mediated by efferent vagal activity acting on the sinus node led investigators to attempt to quantify the fluctuations in R-R intervals that were related to breathing. MATERIALS AND METHODS Nine Zen practitioners with five years of experience took part in the study. Autonomic nervous system function was evaluated by heart rate variability (HRV) analysis during 24-hours ECG recording during zen meditation and at rest. RESULTS The data of this small observational study confirm that ZaZen breathing falls within the range of low frequency HR spectral bands. Our data suggest that the modification of HR spectral power remained also in normal day when the subject have a normal breathing. CONCLUSION We suggest that the changes in the breathing rate might modify the chemoreflex and the continuous practice in slow breathing can reduce chemoreflex. This change in the automonic control of respiration can be permanent with a resetting of endogenous circulatory rhythms.

Polycystic Ovary Syndrome: Androgens, Autonomic Nervous System, and Hypertension

To the Editor: We have read with interest the article by MJ Chen et al1 on the relationship between androgen levels and blood pressure in young women with polycystic ovary syndrome (PCOS). The authors have observed that characteristic hyperandrogenemia in young …

Correlation between glycemic trends assessed by 24 h continuous monitoring and autonomic activity in patients with recent onset type 2 diabetes

We observe, in patients with type 2 diabetes of recent onset, the activity of the autonomic nervous system and glucose metabolic impairment. The data indicate the hyperactivity of the sympathetic and minimal changes in glucose values. The role played by glycemia appeared to be less important than that represented by insulin resistance.

Temporary pacemaker in refractory cluster headache treated with verapamil

Sir,We present a 35-year-old malepatient with 10 years’ history ofepisodic cluster headache (3–4attacks per day, previously treatedwith methysergide, lithium and oxy-gen without significant benefit).Therapy with verapamil 240 mg/dayreduced the frequency of attacks (2–3per day). After increasing the dose ofverapamil to 360 mg/day the patientpresented hypotension (75/40 mmHg)and serious bradycardia (HR 32/min),which required the implant of a tem-porary ventricular non-sequentialpacemaker. Once the critical periodhad passed, the blood pressure nor-malised; after the electrophysiologystudy found normal results, it waspossible to remove the pacemaker.Before starting verapamil therapy,cardiac examination and 24-h ECGrecording were normal.In the last 7 years, we have beenobserving four patients treated withverapamil for episodic clusterheadache that have referred hypoten-sion and serious bradycardia. Thepatients have not presented any con-traindication to prophylactic therapywith verapamil. Verapamil is a calci-um channel blocker and its commonadverse effects include constipation,dizziness, nausea, bradycardia andhypotension. It is widely used as afirst-line prophylactic drug for clusterheadache at doses starting at 360 mg[1, 2]. Patients with cluster headachepresent an increase in sympathetictone before the attack of a headache.This “sympathetic storm” could causeshort but hazardous periods ofarrhythmia [3]. On the contrary, aparasympathetic overactivity withconsequent bradycardia is presentduring the attack [4, 5]. Verapamiltherapy prevents episodic clusterheadache but it requires a strict con-trol of blood pressure and heart rate,because an overlap between theeffects of verapamil and the effects ofthe parasympathetic overactivitycharacterising the attack of clusterheadache that could cause serioushypotension and bradycardia can beverified [6].

Insulin Resistance and Hyperinsulinemia Are Related to Plasma Aldosterone Levels in Hypertensive Patients: Response to Colussi et al.

We read with interest the article by Colussi et al. (1) on the relationship between insulin resistance, hyperinsulinemia, and aldosterone levels in hypertensive patients. The authors observed that the homeostasis model assessment index is correlated with plasma aldosterone. They conclude that in patients with hypertension, this relationship …

Impaired circadian rhythm of cardiac autonomic activity as possible link between insulin resistance and nocturnal nondipping.

With interest we read the article by Afsar et al. [1] on the relationship between insulin resistance and nocturnal nondipping. The authors show that the homeostasis model assessment (HOMA) index is higher in nondipper than in dipper patients and that the HOMA index is positively correlated with nighttime mean arterial pressure and nighttime, daytime and 24-h average heart rates. Moreover, in multivariate analysis, a high HOMA index has been associated with increased nondipping risk. The authors conclude that the HOMA index may be a predictor of nocturnal nondipping in patients with essential hypertension and newly diagnosed type 2 diabetes mellitus.