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Biomedical subjects

L Mainardi

Publications and source records attributed to L Mainardi.

At least 19 recordsLinked to original sources
PubMed1998

Cardiac autonomic patterns preceding occasional vasovagal reactions in healthy humans.

BACKGROUND: The wide range of clinical presentation of orthostatic vasovagal syncope suggests different underlying changes in the cardiac autonomic modulation. METHODS AND RESULTS: To evaluate the beat-by-beat modifications in the neural control of heart period preceding a syncopal event, we studied RR interval variability in 22 healthy subjects who experienced fainting for the first time during a 90 degrees head-up tilt and in 22 control subjects by means of time-variant power spectral analysis. Sympathetic and vagal modulations to the sinoatrial node were assessed by the normalized power of the low-frequency (LF, approximately 0.1-Hz) and high-frequency (HF, approximately 0.25-Hz) oscillatory components of RR variability. When the patients were supine, no differences were observed in the hemodynamic and spectral parameters of the 2 groups. During the tilt procedure, RR, LFNU, and HFNU (NU=normalized units) values were relatively stable in control subjects. During early tilt (T1), subjects with syncope had reduced RR intervals compared with control subjects. In 13 subjects with syncope, RR decreased while LFNU and LF/HF increased in the last minute of tilt before syncope (T2). Conversely, in the remaining 9 fainters, LFNU and LF/HF decreased from T1 to T2 and HFNU increased slightly. CONCLUSIONS: Two different patterns may be recognized in the cardiac autonomic changes preceding an occasional vasovagal event, namely, one characterized by a progressive increase of the marker of cardiac sympathetic modulation up to the onset of syncope, the other by a sympathetic inhibition with an impending vagal predominance. The recognition of different pathophysiological mechanisms in fainters may have important therapeutic implications.

Adolescent↗
PubMed1997

A multivariate time-variant AR method for the analysis of heart rate and arterial blood pressure.

This paper approaches the problem of short-term mechanisms that regulate heart rate and blood pressure variability signals, by focusing the evident changes of their frequency content during transients (dynamic situations in which the behaviour of these control mechanisms may vary on a beat-to-beat basis). In this study, we suggest an autoregressive time-variant spectral estimation method, which is able to follow such dynamic changes in the signals. This method has also been extended to a multivariate approach in order to take into account more than one process at a time, and to assess the mutual influences between the different controlling systems. The algorithms successfully tested on simulated series have also been used to analyse series recorded during a vaso-vagal syncope episode in a tilt manoeuvre and a physical exercise stress test protocol. The results show how this method is able to follow the changing dynamics of the signals on the basis of a closed-loop model of their interaction on a beat-to-beat basis. After a proper identification procedure of the blocks forming the model, it is possible, therefore, to obtain the classical spectral parameters and the gain of the transfer function between the signals. Such parameters constitute new time series that describe the physiopathology of the cardiovascular control systems, even during non-stationary epochs.

Algorithms↗
PubMed1996

Linear multivariate models for physiological signal analysis: theory.

The general linear parametric multivariate modelling concept is presented. This model combines a variety of different kinds of multivariate linear models. The concept of partial spectral analysis is derived from the general model. Some emphasis is laid on the causality demands of the model, and it is shown that the classic strictly-causal structure must be abandoned in order to utilise the modelling in many practical situations. Two special sub-class models are described in detail: the multivariate autoregressive model and the multivariate dynamic adjustment model. Furthermore, time-varying modelling is considered. The modelling of the real system is presented on a general level as a system identification cycle. The application of the methods to real physiological data is presented in the companion paper.

Data Collection↗
PubMed1996

Linear multivariate models for physiological signal analysis: applications.

Some applications of linear multivariate modelling methods in the analysis of physiological signals are presented. These applications illustrate the methods in the analysis of cardiovascular dynamics, which has been one of the main application fields of the multivariate modelling during the last ten years. It is demonstrated that physiologically meaningful information about the causal interactions in the cardiovascular system can be drawn from the routinely available clinical signals. Both static and dynamic conditions are considered.

Humans↗
PubMed1993

Time-variant power spectrum analysis for the detection of transient episodes in HRV signal.

A time-variant algorithm of autoregressive (AR) identification is introduced and applied to the heart rate variability (HRV) signal. The power spectrum is calculated from the AR coefficients derived from each single RR interval considered. Time-variant AR coefficients are determined through adaptive parametric identification with a forgetting factor which obtains weighed values on a running temporal window of 50 preceding measurements. Power spectrum density (PSD) is hence obtained at each cardiac cycle, making it possible to follow the dynamics of the spectral parameters on a beat-by-beat basis. These parameters are mainly the LF (low frequency) and the HF (high frequency) powers, and their ratio LF/HF. These together account for the balanced sympatho-vagal control mechanism affecting the heart rate. This method is applied to subjects suffering from transient ischemic attacks. The time variant spectral parameters suggest an early activation of LF component in the HRV power spectrum. It precedes by approximately 1.5-2 min the tachycardia and the ST displacement, generally indicative of the onset of an ischemic episode. The results suggest an arousal of sympathetic system before the acute attack.

Algorithms↗
PubMed1991

High-performance liquid chromatographic determination of iothalamic acid in human plasma and urine.

A simple, rapid and sensitive method for the determination of iothalamic acid (IA) in both plasma and urine is reported. After extraction with ethyl acetate, IA was determined by strong anion-exchange high-performance liquid chromatography with ultraviolet detection at 254 nm. The lower limit of detection was 0.5 micrograms/ml. The average recovery was 73 and 57% from plasma and urine, respectively. Linearity was found over the investigated concentration range (up to 500 micrograms/ml for plasma and up to 10.0 mg/ml for urine). The reproducibility of the technique was good (coefficient of variation less than 6%) as was the precision and accuracy (coefficient of variation less than 2.5%). No interference from endogenous substances or any of the common drugs tested was found.

Acetates↗
PubMed1990

[Efficacy of photochemotherapy in a case of pityriasis rubra pilaris].

The therapeutic choice in treating Pityriasis Rubra Pilaris (PRP) is difficult, particularly in extensive erythrodermic forms and in those characterized by a strong tendency to recur. None of the therapeutic modalities till now employed have been proved to be resolutive. The curative potential of photochemotherapy in the treatment of PRP has been particularly uncertain. Here a case of recurrent PRP in an adult female subject is reported. The disease covered about 90% of the skin surface and was treated by means of photochemotherapy (total dose: 179.56 J/cm2). A complete remission of the disease has been obtained and is still maintained nine months after the end of the treatment.

Adult↗
PubMed1990

[Results of radiotherapy in 22 patients with epidemic Kaposi's sarcoma].

Radiotherapy is a first choice treatment of skin and oral cavity lesions of epidemic Kaposi sarcoma. It has cosmetic aims in the early stages of the disease, and palliative ones to reduce soreness and associated oedema in the lesions of a more advanced disease. This treatment modality has few side effects and does not modify the immunological condition of the patients. These statements, as they result from the review of the related literature, are here assessed by the experience of the Authors in a series of 22 patients, treated by means of orthovoltage radiotherapy, which allows intracavitary treatments (contact X-ray therapy) and small-sized irradiation fields.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Comparison of the results obtained with ultraviolet radiation and photochemotherapy in the early stages of mycosis fungoides].

The Authors have performed a retrospective study, comparing the results obtained in two groups of patients affected by Mycosis Fungoides at early stages. Thirty-four patients were treated with ultraviolet rays, 32 with photochemotherapy. The patients, in the first stages of the disease, classified on the basis of TNM system, were treated with UVR or PUVA according to standard schedules. The results obtained in the two groups were the following: 1. UVR treated group: complete remission 32%, partial remission 65%, no results 3%; 2. PUVA treated group: complete remission 84%, partial remission 16%. These data show the evidence that photochemotherapy is undoubtedly more advantageous than simple phototherapy in inducing complete remission of early Mycosis Fungoides. UVR therapy still presents, however, as a worthwhile non-aggressive therapeutic choice when the disease has not a progressive character or when photochemotherapy has serious contraindications.

Follow-Up Studies↗
PubMed1975

The therapeutic activity of diftalone in rheumatoid arthritis: crossover comparison with indomethacin.

A multi-centre double-blind crossover study was carried out in 70 hospitalised patients with rheumatoid arthritis to compare the activity of diftalone, a new anti-inflammatory agen, with that of indomethacin. Patients received either 750 mg. diftalone or 100 mg. indomethacin daily for 2 weeks and were then crossed over to the alternative treatment for a further 2 weeks. Routine clinical and laboratory assessments of disease activity were carried out before the start of the trial and after each treatment period. The results indicate that both drugs produced a favourable response and that there was no statistically significant difference between them in the parameters measure, except for the erythrocyte sedimentation rate which fell only after the administration of diftalone. Patient and physician assessments on the course of the disease were in general agreement and were favourable to the same extent for both treatments. Both products were well tolerated and there were few reports of side-effects.

Adult↗