Biomedical subjects

I Pinhas

Publications and source records attributed to I Pinhas.

4 recordsLinked to original sources

PubMed2003

Early autonomic malfunction in normotensive individuals with a genetic predisposition to essential hypertension.

One of the primary pathologies associated with hypertension is a complex autonomic dysfunction with evidence of sympathetic hyperactivity and/or vagal withdrawal. We investigated the possibility for early detection of essential hypertension on the basis of the analysis of heart rate (HR) and blood pressure fluctuations, which reflect autonomic control. Young adult normotensive offspring of one hypertensive parent (KHT; n = 12) and normotensive offspring of two normotensive parents (YN; n = 14) participated in this study. ECG, continuous blood pressure, and respiration were recorded during steady-state conditions and under various autonomic challenges. Time-frequency decomposition of these signals was performed with the use of a continuous wavelet transform. The use of the wavelet transform enables the extension of typical HR variability analysis to non-steady-state conditions. This time-dependent spectral analysis of HR allows time-dependent quantification of different spectral components reflecting the sympathetic and parasympathetic activity during rapid transitions, such as an active change in posture (CP). During an active CP from the supine to standing position, KHT demonstrated a significantly greater increase in the low-frequency fluctuations in HR than YN, indicating enhanced sympathetic involvement in the HR response to CP, and a reduced alpha-index, indicating decreased baroreceptor sensitivity. On recovery from handgrip, vagal reactivation was more sluggish in KHT. These results indicate the early existence of malfunctions in both branches of autonomic control in individuals at increased risk of hypertension.

Adult↗

PubMed2003

Very high frequency oscillations in the heart rate and blood pressure of heart transplant patients.

The authors studied the recently reported very high frequency (VHF) peaks in the heart rate (HR) and blood pressure (BP) power spectra of heart transplant (HT) patients. These VHF peaks appear at frequencies much higher than the respiratory frequency, in addition to the typical low-frequency and high-frequency peaks. Twenty-five recordings obtained from 13 male HT patients (0.5-65 months following surgery) were compared with recordings from 14 normal male subjects. The ECG, continuous BP and respiration were recorded during 45min of supine rest. Eight recordings from HT patients were excluded owing to arrhythmias. Spectral analysis was performed on all other recordings. VHF peaks were found in the spectra of both BP and HR in nine recordings obtained from six HT patients. In some cases, the power in the VHF peaks was markedly higher than that of the high-frequency peak. No VHF peaks were observed in eight recordings obtained from four HT patients or in recording from any of the normal subjects. No correlation was found between the incidence of VHF peaks and time after transplant. It was proved that the VHF peaks were not artifactual, and their significance within the framework of the theory of communication systems is discussed. The presence of those peaks was attributed to vagal denervation.

Adult↗

PubMed2002

Does synchronization reflect a true interaction in the cardiorespiratory system?

Cardiorespiratory synchronization, studied within the framework of phase synchronization, has recently raised interest as one of the interactions in the cardiorespiratory system. In this work, we present a quantitative approach to the analysis of this nonlinear phenomenon. Our primary aim is to determine whether synchronization between HR and respiration rate is a real phenomenon or a random one. First, we developed an algorithm, which detects epochs of synchronization automatically and objectively. The algorithm was applied to recordings of respiration and HR obtained from 13 normal subjects and 13 heart transplant patients. Surrogate data sets were constructed from the original recordings, specifically lacking the coupling between HR and respiration. The statistical properties of synchronization in the two data sets and in their surrogates were compared. Synchronization was observed in all groups: in normal subjects, in the heart transplant patients and in the surrogates. Interestingly, synchronization was less abundant in normal subjects than in the transplant patients, indicating that the unique physiological condition of the latter promote cardiorespiratory synchronization. The duration of synchronization epochs was significantly shorter in the surrogate data of both data sets, suggesting that at least some of the synchronization epochs are real. In view of those results, cardiorespiratory synchronization, although not a major feature of cardiorespiratory interaction, seems to be a real phenomenon rather than an artifact.

Algorithms↗

PubMed1978

Progressive supranuclear palsy: electomyographic examinations of eye muscles.

Electromyographic examination of vertical and lateral extraocular muscles was carried out in five patients suffering from progressive supranuclear palsy, and incapable of performing voluntary vertical eye movements. No evidence of a lower motor neurone lesion or paradoxical innervation of eye muscles was noted. Reciprocal inhibiton of antagonist vertical muscles though present in oculocephalic (doll's head) stimulation, was incomplete on attempted voluntary movement. This factor is held to be the probable immediate cause of the vertical gaze palsy.

Action Potentials↗