Biomedical subjects

Alberto Malliani

Publications and source records attributed to Alberto Malliani.

22 records · Page 2Linked to original sources

PubMed2002

Opposite effects of iv amiodarone on cardiovascular vagal and sympathetic efferent activities in rats.

It is unknown whether amiodarone exerts a direct central action on the cardiovascular autonomic nervous system. This study was designed to evaluate the effects of acute amiodarone administration on vagal and sympathetic efferent nerve discharges. Experiments were carried out in 25 decerebrate unanesthetized rats. In one group, vagal activity was recorded from preganglionic fibers isolated from the cervical vagus nerve. In another group, sympathetic recordings were obtained from fibers isolated from the cervical sympathetic trunk in intact conditions or after barodenervation. Recordings were performed before and for 60 min after amiodarone (50 mg/kg iv) administration. In all groups, amiodarone induced bradycardia and hypotension. Vagal activity increased immediately, reaching a significant difference after 20 min (260 +/- 131% from 16.4 +/- 3.3 spikes/s) and was unmodified by the barodenervation. At difference, sympathetic activity after an initial and short-lasting increase (150 +/- 83% from 24.8 +/- 5.7 spikes/s) began to decrease significantly after 20 min (36 +/- 17%) throughout the experiment. The initial increase in sympathetic activity was not observed in barodenervated animals. These changes in vagal and sympathetic activity could play an important role in contributing to the antiarrhythmic action of amiodarone.

Amiodarone↗

PubMed2002

Emerging excitatory role of cardiovascular sympathetic afferents in pathophysiological conditions.

There is sound experimental evidence that cardiovascular sympathetic afferent fibers mediate cardiovascular reflexes largely excitatory in nature with positive-feedback characteristics. This afferent neural channel is likely to normally participate in the neural regulation of cardiovascular function. The hypothesis, which is the core of this article, is that in some pathophysiological conditions, sympathetic overactivity may be partly due to an emerging excitatory reflex action of cardiovascular sympathetic afferents. In fact, the early phase of congestive heart failure can be characterized by an increase in arterial pressure and heart rate and/or by a diastolic dysfunction, leaving unchanged the cardiac output; in these conditions, in which no baroreceptor deactivation should occur, it is possible that cardiovascular sympathetic afferents with sensory endings in the thoracic low-pressure areas, highly responsive to volume loading, are responsible for mediating the reflex sympathetic excitation. Similarly, during acute myocardial infarction, ventricular sympathetic afferents are likely to mediate a reflex sympathetic overactivity, which is known to facilitate sudden death. Finally, numerous reports have described in essential arterial hypertension an increased sympathetic activity that may be due, at least in part, to the reinforcing action of sympathosympathetic reflexes. Thus, in pathophysiological conditions, cardiovascular sympathetic afferents would mediate a reflex sympathetic overactivity independently of baroreceptive mechanisms, and such an absence of a homeostatic purpose would provide a better rationale for some beneficial effects of therapeutic correction.

Animals↗

PubMed2002

Heart rate variability as a clinical tool.

Power spectrum analysis of cardiovascular signal variability, and in particular of the RR period (heart rate variability), is a widely used procedure for the investigation of autonomic cardiovascular control and/or target function impairment. However, a correct methodology is essential to extract the information embedded in the frequency domain. This article has the main purpose of proposing a still wider clinical use of the spectral methodology. Indeed, with this procedure the state of the sympathovagal balance modulating the sinus node pacemaker activity can be quantified in a variety of physiological and pathophysiological conditions. Changes in the sympathovagal balance can be often detected in basal conditions; however, a reduced responsiveness to an excitatory stimulus is the most common feature that characterizes numerous pathophysiological states. Moreover, the attenuation of an oscillatory pattern or its impaired responsiveness to a given stimulus can also reflect an altered target function and thus can furnish interesting prognostic markers.

Algorithms↗

PubMed1999

The Pattern of Sympathovagal Balance Explored in the Frequency Domain.

In most physiological conditions, sympathetic and vagal activities modulating heart period undergo a reciprocal regulation, leading to the concept of sympathovagal balance. This pattern can be indirectly quantified by computing the spectral powers of the oscillatory components corresponding to respiratory acts (high frequency) and to vasomotor waves (low frequency) present in heart rate variability.

Journal Article↗