Biomedical subjects
Publications and source records attributed to G Grassi.
The complex problem of drug-taking during pregnancy is examined. Clinical and metabolic effects on the baby at birth, amounting to withdrawal effects, are described. The importance of prophylactic and therapeutic abstinence during gestation, birth and the period following birth is emphasised.
The effects of selective deactivation and stimulation of cardiopulmonary receptors on plasma noradrenaline (radioenzymatic method) were studied in nine normotensive subjects by reducing and increasing central venous pressure for 20 min via lower body suction and leg-raising manoeuvres that did not alter arterial blood pressure and heart rate. Deactivation of cardiopulmonary receptors was accompanied by a rise in plasma noradrenaline that achieved a peak within 5 min (91.8 +/- 22%, mean +/- SE) and was then sustained. Stimulation of cardiopulmonary receptors was accompanied by a fall in plasma noradrenaline (-16.6 +/- 3.4%) that levelled off at the second minute and was then sustained. On average the increase and the reduction in plasma noradrenaline had a time course and a magnitude similar to the increase (80.5 +/- 10.5%) and the reduction (-28.4 +/- 5%) in forearm vascular resistance (derived from plethysmographic flow measurement) concomitantly caused by cardiopulmonary receptors. Furthermore, analysis of individual data showed that changes in plasma noradrenaline and forearm vascular resistance were linked by a positive relationship (r = 0.64). Thus the cardiopulmonary receptor reflex can produce rapid, marked and sustained changes in both plasma noradrenaline and forearm vasomotor tone. This is in sharp contrast with the previously observed inability of the carotid baroreflex to alter both these humoral and haemodynamic variables. Taken together these findings support the hypothesis that sympathetic tone to skeletal muscle is an important determinant of the concentration of plasma noradrenaline in blood.
Although studies of the cardiovascular control exerted by arterial baroreceptors in man are limited by technical and ethical problems, the variable-pressure neck-chamber technique has provided a considerable amount of information about this topic. This paper focuses on the carotid baroreceptor reflex as evaluated by studies using the neck-chamber technique and examines this control in a number of physiological and pathophysiological states. The results of these studies suggest that in normotensive subjects the set-point of the reflex is located eccentrically toward its saturation, which makes this homeostatic mechanism more effective in counteracting a blood-pressure fall than a blood-pressure rise. They also suggest that the concept of an impairment of the arterial baroreflex in aging, exercise, and hypertension, though valid for the baroreceptor control of heart rate, is no longer tenable for the baroreceptor control of arterial pressure. The paper also reviews in humans the effects of arterial baroreceptors on regional circulations and on the excretion of humoral substances such as renin, and compares them with those of the cardiopulmonary receptors. It is suggested that the latter predominate over the former in the reflex modulation of plasma-renin activity, and that this is part of a homeostatic mechanism for blood-volume control.
Several lines of evidence indicate that angiotensin II (ANG II) may potentiate the vascular response to sympathetic stimulation. However, there are no clear signs that this action of ANG II is physiologically relevant in man. To investigate this problem, we used the lower body negative pressure technique (LBNP, -15 mmHg) to deactivate cardiopulmonary receptors and reflexly stimulate the sympathetic nervous system. The haemodynamic (changes in blood pressure, heart rate, central venous pressure, forearm blood flow) and humoral effects [changes in plasma noradrenaline (PNA) and plasma renin activity (PRA)] of this manoeuvre were examined before and after blockade of angiotensin formation achieved by the administration of the converting enzyme inhibitor, captopril. Studies were performed in patients with essential hypertension in control conditions and after acute and chronic captopril treatment. We found that the reduction in forearm blood flow induced by LBNP was significantly diminished after acute and chronic captopril in spite of the fact that the fall in central venous pressure and the increases in PNA were similar to those observed in control conditions. In contrast, the response of renin to LBNP was enhanced, at least after acute captopril administration. These findings suggest that efficiency of the reflexes originating from the cardiopulmonary receptors is impaired after captopril. Angiotensin II contributes to the vasoconstrictive ability of the sympathetic nervous system, either through a direct vascular action or by enhancing the vascular responsiveness to noradrenaline stimulation. However, this sympathetic facilitatory action of ANG II does not appear to be extended on the adrenergic mechanisms which regulate renin release.
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The use of programmed electrical 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 these features is not yet available and, thus, a temporary external lead is required. These difficulties have been overcome by utilizing radiofrequency to synchronize and stimulate. An implantable device was therefore designed which is triggered by the patient and automatically searches the interruption zone of the tachycardia by exploring the R-R cycle. The external transmitter, which can produce one or two synchronized impulses, is programmed to scan the R-R cycle with progressive steps of 5 or 10 ms; when tachycardia is interrupted, further stimulation is inhibited. The implanted module connected to an endocavitary lead does not have any power supply and, therefore, is very small. The efficacy of this method has been demonstrated in 4 patients with supraventricular tachycardia (3 with WPW syndrome) resistant to conventional pharmacologic therapy.
Fifty nine cases of open diaphyseal fractures of the long bones treated by rigid osteosynthesis were examined with reference to their course and outcome in relation to whether the operation was immediate of deferred. No significant differences arose as between the two groups of cases. It thus appears that the timing of the operation has no important repercussions on the course and the result.
The AA. described an external stimulator to be utilized instead of invasive pharmacological treatment, as a short and middle-time therapeutic approach to re-entry tachycardia, in Departments of cardiology. The device must be connected with an electrode placed in atrium or in coronary sinus or in ventricle, according to individual request. A frequency discriminant device recognizes tachycardia and activates automatic scanning stimulator, synchronized on R or P waves, with progressive 5 msec stop delay; tachycardia interruption zone is automatically individuated. Stimulation has an automatic stop when tachycardia is interrupted; in case of persistent tachycardia scanning-function cycle will star again automatically. The device, which can be programmed for a simple or a double impulse emission, is equipped with a demand stimulator working if post-tachycardia asystole is present. Frequency discriminant device activates the scanning function beyond a defined threshold which can be varied within a wide range of frequencies.
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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.
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.
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.
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.
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.
The authors describe a case of posterior acromio-clavicular dislocation treated operatively. The etiology and pathological anatomy are discussed and the importance of an axial radiographic projection is emphasized. Radiographic comparison with the normal shoulder is helpful in leading to a correct diagnosis.
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.
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.
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