G. Calcagnini

Sympathetic-Parasympathetic Activation During Spontaneous Attacks of Cluster Headache: Evaluation by Spectral Analysis of Heart-Rate Fluctuations

Twenty-four hour ECG Holter and blood-pressure monitorings were performed in eight patients suffering from cluster headache. Spectral analysis of heart-rate fluctuation was used to assess the autonomic balance under basal conditions, after head-up tilt, and during a spontaneous attack. Normal autonomic balance was found at rest and during sympathetic activation obtained with head-up tilt in the interparoxysmal period. Before the onset of headache, an increase in the low-frequency (LF) component of the power spectrum was apparent in all patients. This sign of sympathetic activation was followed by an increase in the high-frequency (HF) component that developed about 2000 beats after the onset of headache and rapidly overcame the LF component until the end of pain. Significant differences were found when comparing the spectral parameters [total spectral values (TP), power of the LF and HF components and LF/HF ratio] obtained before, during and after headache. During the attack, blood pressure increased and heart rate decreased in all subjects. There appears to be a primary activation of both sympathetic and parasympathetic functions in cluster headache attacks. The sympathetic component seems to be involved mostly in the development of the attack, whereas the parasympathetic activation seems to occur, following the onset of the attack, independently of the pain.

Cardiovascular autonomic rhythms in spontaneous pupil fluctuations

The aim of this paper was to investigate the relationship between spontaneous pupil diameter fluctuations and autonomic rhythms of cardiovascular variability signals. ECG, Finapres and respiration data from 10 normal subjects were recorded simultaneously to spontaneous pupil diameter fluctuations obtained from a portable infrared TV pupillometer. Power spectra of pupillary fluctuations showed in all the subjects a respiratory component with significant spectral coherence with the high frequency components of the tachogram and systogram. Moreover a discrete power distribution in the low frequency band have been identified; coherence with LF power in tachograms and systograms was significant in 6/10 subjects. It is concluded that cardiovascular autonomic rhythms can be detected in spontaneous pupil diameter fluctuations.

24-Hour Blood Pressure Profiles in Patients with Hypertension Treated with Amlodipine or Nifedipine GITS

SummaryAn open crossover trial was conducted to compare the effects of 2 long-acting dihydropyridine calcium antagonists, amlodipine (5 to 10 mg/day) and nifedipine GITS (gastrointestinal therapeutic system) [30 to 60 mg/day], in 40 patients with mild to moderate essential hypertension. Particular attention was given to performance of the 2 drugs during the early morning hours. Each phase of treatment lasted 12 weeks. After an initial drug washout period (and at the end of each phase), 24-hour noninvasive ambulatory blood pressure monitoring (ABPM) was performed. In addition, sphygmomanometric measurements were obtained at regular intervals during treatment.Both drugs significantly reduced sitting blood pressure (measured with a sphygmomanometer) and daytime, night-time and 24-hour mean ambulatory blood pressures; on the basis of these parameters, no significant differences were found between the 2 drugs. However, multivariate analysis of ABPM data revealed that amlodipine had greater antihypertensive efficacy than nifedipine GITS (in terms of systolic and diastolic reductions) between 0500 and 1100 hours (p < 0.02 vs nifedipine GITS).

SMS-based platform for cardiovascular tele-monitoring

The focus of this paper is to describe a fully automatic platform to transmit, using the SMS service, medical data collected at home. The overall platform has two main components: a central server for SMS receiving (Central Receiving Unit, CRU) and the remote sending data collection and transmitting units (Home Transmitting Unit, HTU). HTU is connected to commercial meters of arterial pressure and blood glucose, and to a stepcounter. The CRU is located in a clinical center and acts also as a server for the database housing and for the users applications (data display, trend visualizations, alarms). Five platforms (CRU+5HTU) have been realized and given to patients. During a cumulative monitoring period of 251 days, there were 175 data transfer sessions, a mean of 35 plusmn 20 per patient. The stability of the telemonitoring system and the mean percentage of successful encoding of the transmitted data were 100%.

Multidisciplinary approach for diagnosing syncope: a retrospective study on 521 outpatients

Objectives: To describe causes of syncope in outpatients in whom structural heart disease was ruled out as a cause, and to analyse the role of a multidisciplinary approach in a syncope unit for the diagnosis of patients with syncope of unknown origin. Methods: Cardiovascular autonomic nervous system (ANS) function was evaluated extensively in 521 outpatients by careful history, physical examination including orthostatic blood pressure measurement and standard ECG, and tilt testing. Results: Causes of syncope remained unknown in 29.2% of cases. ANS dysfunction was found in 58.6% of those presenting with either neurally mediated syncope (53.6%) or chronic autonomic failure (5%); 3.8% of the patients suffered from syncope of cardiogenic origin (2.5%) or non-neurogenic hypotension (1.3%), and 8.4% had loss of consciousness of non-syncopal origin. Loss of consciousness was confirmed as being related to seizures in under 30% of patients initially diagnosed as having epilepsy. Conclusions: Neurally mediated syncope represents the commonest type of syncope. ANS evaluation including tilt testing should be considered as preliminary screening in patients with syncope in the absence of definite heart abnormalities. Neurologists should consider syncope from ANS failure as a comorbid factor in patients with seizures where the clinical characteristics are not straightforward.

Nonlinear Coupling Among Heart Rate, Blood Pressure, and Respiration in Patients Susceptible to Neuromediated Syncope

AbstractThe aim of this study is to evaluate the degree of coupling between the cardiovascular variability series and the respiration in subjects susceptible to neurally mediated syncope. Twenty-one informed patients susceptible to syncope and ten sex- and age-matched control subjects were enrolled in the study. ECG, respiration activity, and arterial blood pressure were simultaneously recorded at rest (controlled and free breathing) and during the 70° head-up TILT test (free breathing). The degree of nonlinear coupling among heart rate variability (HRV), blood pressure variability (BPV), and respiration was quantified by means of two indices according to a multivariate embedding-based approach. Eleven patients developed syncope during the TILT test. We found that during the late TILT phase, the TILT-positive group experienced a significant increase in nonlinear coupling respect to the mid TILT phase (p < 0.01, Wilcoxon nonparametric test for pair data) while the TILT-negative group did not (p < 0.01, Mann-Whitney U-test). If the proposed nonlinear coupling indexes can be considered expression of the coupling mechanisms involved in the vagal regulation of the cardiovascular system, an increase in vagal tone accompanied by a decrease in sympathetic activity seem to occur before a vasovagal event.

Effects of internal cardioversion on electrophysiological properties of the right atrium

Aim of this study is to investigate the effects of low energy internal cardioversion (LEIC) on the electrophysiological properties of the right atrial tissue. Thirteen patients were studied, selected a priori for LEIC (increasing energy levels: 1, 2, 3, 5, 7, 10, 15 and 20 J) and monitored by a multipolar basket catheter (32 intra-atrial recordings each patient). The atrial period, the levels of organization and the synchronization have been estimated for each electrogram, over 10-second windows, 10 seconds before and 10 seconds after each shock. Our results suggest that ineffective shocks do not affect the electrophysiological properties of the atria. This is consistent with the hypothesis that even though electrical activation ceases after the shock it spontaneously regenerates within few milliseconds and that the propagation pattern is expression of the organic substrate, which is not affected by an electric shock.

Self-similar properties of long term heart rate variability assessed by discrete wavelet transform

The aim of this study was to test the self-similar properties of 24 h Holter Heart Rate Variability (HRV) data using the Discrete Wavelet Transform (DWT), in a population of hypertensive patients, compared with a normal group. For the DWT analysis we used a 2/sup nd/ order Daubechies filter according to theoretical considerations on nonstationarity, border effects and numerical efficiency. We estimated the 1/f spectral exponent as either the slope of the log-log plot of the power spectrum (/spl alpha/-FFT) and the slope of the semilog plot of the DWT details variances vs. the scale (/spl alpha/-DWT). In hypertensive patients, /spl alpha/-FFT was 1.14/spl plusmn/0.10 and /spl alpha/-DWT was 1.1/spl plusmn/0.09; in normal subjects, /spl alpha/-FFT and /spl alpha/-DWT were 1.08/spl plusmn/0.11 and 1.06/spl plusmn/0.07, respectively. These results suggest the DWT as a robust and efficient method to characterize long term HRV self-similarity, overcoming the limitations of the classical FFT approach for 1/f processes.

Recurrence plot analysis of the coupling between respiration and cardiovascular variability signals

The authors performed a quantitative study of sub-harmonic synchronization and entrainment phenomena between respiration and short-term Heart Rate and Blood Pressure variability signals by the Recurrence Plot Analysis (RPA). Quantification of the recurrence plots has been obtained using descriptors such as Percent Recurrence, Percent Determinism and Entropy of Recurrences. The authors applied RPA to data obtained in control breathing at different frequencies from 10 normal subjects. The breathing frequencies were chosen to elicit interference phenomena between LF and HF frequency components. Unlike the power spectral estimation, RPA seems to be succeeds in detecting entrainment and transient phase locking phenomena; moreover, the recurrence descriptors turn out to be particularly suited for a quantitative evaluation of the different phenomena observed.

Power spectrum density estimation (1/f spectrum) of long term heart rate variability in acute myocardial infarction

The power spectrum density of the heart rate beat to beat variability signal of healthy subjects, shows a power law (1/f) behaviour over a time scale ranging from a few minutes to hours. Long term PSD (24 hour Holter recording, frequency range: 0.00001-0.01 Hz) has been estimated in 15 patients who survived myocardial infarction, within 48 h, and after 1 month. PSDs in the acute phase do not show 1/f behaviour, while they seem to recover after one month. The effect of daily physical activity has been also investigated in healthy volunteer subjects resting in bed for 24 h. Preliminary results for this group showed an 1/f PSD. Unfortunately the physiological meaning of such a type of spectrum is not clear and several different underlying mechanism are likely to be involved.