Active implantable device

Details Active implantable device Active implantable device

1998-07-14

2002-06-04

Evanisko, George R. (Department: 3762)

Surgery: light, thermal, and electrical application

Light, thermal, and electrical application

Electrical therapeutic systems

Reexamination Certificate

active

06400987

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to implantable devices (or implants) of active type.
BACKGROUND OF THE INVENTION
This term “implants” is intended to indicate devices intended to be implanted in the body of a patient and the function of which is not limited to the replacement or functional assistance of an organ or a part of an organ of the human body (which may be the case, for example, with a cardiac valve prosthesis or so-called vascular graft). On the contrary, an active implantable device is generally able to recognise the occurrence of a particular physiological picture and then give a specific reaction.
Cardiostimulators (currently known as pacemakers) are a typical example of active implantable devices: these latter are in general able to recognise the absence or insufficiency of the natural cardiac stimulation and to respond in such a way as to replace this missing or insufficient stimulation with a stimulation produced by the device itself, acting as a function of the activity of the patient (so-called “rate responsive” stimulators).
It is also known that implant devices such as cardiostimulators as mentioned above, can be provided with a so-called telemetry function which, as well as allowing programming of the stimulator from a distance (and therefore in an extracorporeal manner), also makes it possible to emit, for example to a monitoring station supervised by an operator, signals indicative of the conditions of the wearer.
Also known in the art are so-called “drug dispenser” implants which are able to achieve a targeted delivery of a predetermined drug, also in dependence on a signal indicative of the establishment of particular conditions in the body of the patient.
The present invention, which has been developed with a view to preferential (although not exclusive) application to the treatment of cardiac conditions, is based on the recognition of several essential facts:
almost all active implants available up to now are only able to treat cardiac conditions of the “electrical” type, such as for example insufficient stimulation;
some electrical cardiac conditions (such as for example, atrial fibrillation) are not treatable in a satisfactory manner with only electrical stimulation, whilst, on the other hand, important results in the treatment of such conditions have been obtained with a pharmaceutical treatment; and
important cardiac conditions (such as the so-called congestive heart failure, currently called CHF) are difficult to monitor, expensive to treat and often have unfavourable consequences if not monitored and treated in a timely manner.
By examining more closely the two above-considered conditions (which it is intended should not exhaust the range of possible applications of the invention) the following can be observed.
Atrial fibrillation is essentially a form of cardiac arrhythmia characterised by rapid and irregular atrial electrical impulses and by inefficient atrial contractions. The atrial rhythm can be up to 400-650 beats per minute, whilst the ventricular rhythm varies in an irregular manner between 100 and 180 beats per minute. Atrial fibrillation can have a paroxysmic origin at different points of the sinoatrial node and is typically multifocal. It may terminate spontaneously in an unexpected manner, but often becomes chronic.
The consequences lead substantially to a loss of effectiveness of the atrial contraction (the so-called “atrial kick”) and to a loss of the correct management of the cardiac frequency according to metabolic requirements (so-called chronotropic incompetence), and to the frequent manifestation of arrhythmias with an irregular and rapid ventricular rhythm. All this leads to a general reduction of efficiency in the pumping action of the cardiac muscle (unbalanced, low resistance to forces), to an increase in the formation of intracardiac thromboses (with consequent risk of cerebral ictus), to ventricular tachycardia, and, in general, to a reduced quality of life with increasing risk of mortality.
The main methods of treatment currently known range from surgical treatment (which is traumatic and certainly not suitable in all cases) to external electric defibrillation (which at times is not effective and may not be in time) to ablation of the ectopic sites at the base of the arrhythmias (a technique which must, however, remain of an experimental nature), to pharmacological treatment. This latter type of treatment, which is of an anti-rhythmic nature, is essentially directed at reducing the recurrence of fibrillation (by administration of quinidine, flecainide, propafenone, sotalol or disopyramide), reducing the cardiac frequency (by the administration of digitalis products and b-blockers) or has an anti-coagulant function to reduce the risk of ictus and other thromboembolic events (administration of aspirin, warfarin), and is certainly promising, but is not conclusive in that it is not free from contra-indications or risks.
It is possible therefore to assert that in order to be certainly effective of treatment must to some extent be able to count at least in principle, on at least some of the forms of treatment described above, performed in a co-ordinated framework of concurrent actions of diverse nature.
This is also substantially true for congestive heart failure (CHF). This latter essentially leads to a weakening and then a reduced function of the cardiac muscle as a pumping member, and is in particular able to cause significant difficulty in filling and/or emptying of the left ventricle and therefore an insufficient cardiac capacity.
The main consequences are dispnea and a greater sense of fatigue from effort, ventricular arrhythmia (and in particular atrial fibrillation), an increase in sympathetic tone with a reduction of parasympathetic tone, thromboembolisms, retention of fluids and an increased risk of myocardiac infarction. All this with a significant increase in the mortality rate in particular by unexpected death and by terminal cardiac insufficiency.
The current methods of treatment are pharmacological, with the administration of digitalis products, diuretics or vasodilators. Such treatment, which is not always effective and the therapeutic effect of which is not demonstrated, can be the herald of collateral effects.
Electrical stimulation has also been practised, which however is of limited effectiveness and is only usable in a small category of patients, the same considerations applying to the technique of cardiomyoplasty.
A greater effectiveness, at least in some cases and on a temporary basis, can be achieved by recourse to ventricular assistance devices (VAD) or to artificial hearts. This, however, involves, as is well known, arrangements which are usable for only a limited time, and are such as to require intensive hospital assistance (with consequent high treatment costs), involving intrinsically more difficult techniques allied to the fact that ventricular assistance devices usually require, for their operation, service supply means (electrical energy, fluid under pressure etc.) from sources located outside the body of the patient, via supply lines of a transcutaneous nature.
A limited solution is represented by (total or partial) transplant of the cardiac muscle, a solution which however comes up against limited availability of donors, problems of biocompatability, high initial and follow up costs and risks of possible degeneration.
The experience of treating these conditions demonstrates that very often the possibility of achieving an effective treatment, whatever its type, depends critically on the possibility of monitoring the patient's condition and/or signalling in a timely manner to the outside (to the patient himself and/or to an assistance centre to which he can go) the establishment of or, better still, the probable approach of a crisis state. In this way it is possible, for example, to cause the patient to interrupt an activity which may be critical because of the conditions and/or to go straight to an assistance centre, or even cause the assistance centre, alerted in a

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