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Biomedical subjects

G Critelli

Publications and source records attributed to G Critelli.

At least 91 records · Page 5Linked to original sources
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

[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

[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↗
PubMed1977

Myocardial contractility after injection of prolonged infusion of magnesium sulphate.

The effect of magnesium sulphate administration on myocardial inotropism has been evaluated by means of the noninvasive indexes of myocardium contractility in 18 patients affected by myocardiosclerosis associated with signs of cardiac impairment of different degree. Magnesium has been administered via either a prolonged infusion (30-50 mg/min) or a single injection (2.5 g/30 sec). It is emphasized that the influence of this agent on systolic time intervals (STI) is dependent upon its route of administration. Thus, prolonged infusion does not modify significantly these parameters, whereas a single injection induces marked variations, i.e., decrease of LVET, increase of PEP, ICT and PEP/LVET ratio, which are all more marked in cases of severe cardiac impairment. In view of the strict correlation established between the STI and the invasive indexes of myocardial contractility, it is suggested that administration of magnesium sulphate via prolonged infusion does not induce a decrease of cardiac performance, while a single injection of this agent leads to this effect.

Arrhythmias, Cardiac↗