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Biomedical subjects

G Grassi

Publications and source records attributed to G Grassi.

At least 271 records · Page 15Linked to original sources
PubMed1978

Preliminary experience with the pH-triggered pacemaker.

A cardiac pacemaker capable of responding to blood acidosis by change in its stimulation rate allows adjustment to a patient's metabolic needs. The blood pH is sensed by an iridium oxide electrode in the right atrium. During exercise, the venous pH decreases and the paced ventricular rate increases. If acidosis persists, the paced rate gradually returns to baseline and reaches it after about 70 minutes. A pH-triggered pacemaker has been implanted in a 72-year-old male. The pacemaker remained responsive one year after implant, increasing rate during exercise, cold pressor stress, ischemia of the arms and emotional stress.

Aged↗
PubMed1978

Erythrocyte acetylcholinesterase activity changes in the early stages of anemic and hypobaric hypoxia or after CoCl2 treatment in rabbits.

The authors studied the changes of erythrocyte acetylcholinesterase (AChE) activity in rabbits respectively subjected to bleeding, hypobaric hypoxia and CoCl2 treatment; in such conditions a rise of the enzyme activity was observed. Similar increases take place also as a consequence of intravenous infusions carried out by using lactic or hydrochloric acid. The authors suggest that these increases in the erythrocyte AChE activity are connected with the decrease of the pCO2 that occurs in the various experimental conditions achieved.

Acetylcholinesterase↗
PubMed1978

[Stimulation with automatic radiofrequency scanning in the long term treatment of tachyarrythmias].

A pacemaker is described which uses radiofrequency signals for synchronisation and pacing, and seeks automatically the phase of the cycle at which the tachycardia may be interrupted. The patient himself can activate the pacemaker. The programme of the external transmitter, which scans nearly all the R-R cycles of the tachycardia, may be pre-set to transmit one or two synchronised stimuli, with a progressive delay of 5 or 10 ms. If the tachycardia is interrupted the pacing stops automatically. The implantable unit of the device may be connected to a normal endocardial electrode, has no batteries and is of small size and weight. The method has been used with success in 4 patients with reciprocal junctional tachycardia (3 of these patients had the Wolff-Parkinson-White syndrome), and in one case of chronic recurrent ventricular tachycardia. All of them were refractory to conventional therapy.

Cardiac Pacing, Artificial↗
PubMed1978

[Clinical and biological aspects in patient with pH-triggered implanted pacemaker (author's transl)].

The Authors have selected the variations of blood pH to drive the pacing rate according to the new biological balance created by exercise. The clinical tests performed on the patients who have had a pH-triggered pacemaker implanted one year previously demonstrated that: a) during physical exercise there is an increase of cardiac rate triggered by the pacemaker, comparable with that noted when sinus rhythm is present; b) situations causing an increased production of cathecolamines and thus a pH variation--Cold Pressor Test, Ischaemic Test, as well as emotional stress--cause an increase of the stimulation rate of pH triggered pacemaker.

Blood↗
PubMed1978

[Stimulation by automatic scanning in the long-term treatment of hyperkinetic arrhythmias (author's transl)].

The use of programmed stimulation in the long-term treatment of re-entry tachycardia offers encouraging perspectives. Among the others proposed the "scanning" system seems to be the most effective. However, an implantable stimulator with such pictures is not yet available and a temporary electrode is thus required. These difficulties have been overcome utilizing the radiofrequency as a sincronizing and stimuli-producing means. An implantable appliance was therefore designed which is triggered by the patient himself and automatically researches the zone of interruption of tachycardia by exploring the R-R cycle. The program of external transmitter which can produce one or two sincronized impulses, seams the cycle with progressive steps of 10 msec each; when tachycardia is interrupted, further stimulation is inhibited. The implanted part of the appliance connected with a normal endocavitary electrode, does not have any power supply and thus is very small. The efficacy of this method has been shown in 4 junctional reciprocating and 1 ventricular recurrent chronic tachycardias, resistent to conventional pharmacologic therapy.

Humans↗
PubMed1978

The surgical treatment of Kienböck's disease.

A long term follow up of thirty two patients operated on for Kienböck's disease of the semilunar bone at the Istituto Ortopedico Toscano in the last twenty eight years has been carried out. Three types of operation were performed; excision of the semilunar, lengthening of the ulna, and shortening of the radius. The best results were obtained from shortening the radius. Good results were also obtained in cases in which there was no preoperative relative shortening of the ulna at the inferior radio-ulnar joint.

Adult↗
PubMed1978

[Programmed electrical stimulation in the treatment of reciprocating arrhythmias. Use of radiofrequency as a stimulating and synchronising means (author's transl)].

A new model of radiofrequency stimulator is presented, which can be programmed for the transmission of one or two impulses synchronised and delayed on the endocardial electrogram. This pacemaker was successfully used in jounctional reciprocating tachycardias and in a case of recurrent ventricular tachycardia. The implanted device, connected to the electrode catheter in right ventricle, does not contain energy sources. This lets a little size and allows having outside the body all the program controls, which in the time can have to change, due to variations of the parameters of tachycardias interruption. The implanted receiver is designed to induce in the resonant coil of external transmitter a frequency modulation proportional to the endocavitary signal. A slope detector receives this signal and programs on them the stimulating impulses, transmitted to stop the tachycardia. It is possible to manufacture such a simple device that the same patient can use it. Of course, periodic controls on the patient must be made to assess the cause of the tachycardia.

Cardiac Pacing, Artificial↗
PubMed1978

Early effects of cobalt chloride treatment on certain blood parameters and on urine composition.

The authors studied the variations of some blood parameters and urine composition during the first hours after CoCl2 treatment in rats and rabbits. These showed an increase in hematocrit with a decrease in plasma volume and, at the same time, a decrease in total proteinemia as well as in the albumin (rabbits) and gamma-globulin fractions. On the basis of observations carried out in rabbits, these phenomena are not seen if the cobalt is complexed with cysteine before treatment; moreover, they are at least partly reversed by cysteine administration soon after cobalt. Plasma Na+ and K+ concentrations do not show significant changes in CoCl2-treated rabbits; on the contrary, the excretion of such electrolytes, as well as urinary protein content, decreases. In addition, the urine of CoCl2-treated rabbits contains at least two pigmented substances with different molecular weights, which are separable by dialysis and DEAE-cellulose chromatography and both contain cobalt in different percentages. The authors believe that CoCl2 treatment leads to an early and profound increase in vascular permeability with depletion of plasmatic material in the tissues and hemoconcentration; moreover, the above stated phenomena seem to be correlated with the forming of cobalt complexes.

Animals↗
PubMed1977

Endocardial electrogram amplitudes and stimulation thresholds in monopolar electrodes: possible correlations.

The possible correlations between unipolar endocardial electrogram amplitudes and voltage threshold stimulation were tested with electrodes having metallic tips of two different areas. The threshold measurements were always studied with the same pulse characteristics. The data were analyzed through five mathematical functions (linear, exponential, potential, hyperbola and translate hyperbola). The results show a significant correlation, mainly by hyperbolic and exponential functions. Consequently, we could deduce a parameter value since we already knew the other one. This was possible not only during the first implantation, but also later on.

Adult↗
PubMed1977

[Electrode surface areas, pulse duration and stimulation threshold. Acute and chronic study with endocardial unipolar electrodes (author's transl)].

Acute and chronic voltage-threshold of cardiac stimulation was studied in patients with complete A-V block. Endocardial unipolar electrode with three different cathodial surface areas were used (54, 22 and 12 sqmm), and tested with rectangular stimulus of variable duration (from 0.2 to 3.5 msec.). The results show that the threshold values, at first implantation and at pulse-generator replacements, are low when short-duration stimulus and smaller electrode surface area are used. The practical advantages of this study are evident.

Electric Stimulation↗