RF COIL FOR STIMULATION SYNCHRONOUS WITH THE "R" WAVE

Field of the invention

The present invention relates to an implantable defibrillation system equipped with a coil coupled to the pacemaker and an external component equipped with radio frequency (RF) output antenna. The internal coil can be equipped with a stimulation electrode of its own or else is fitted directly on the stimulation electrode of the pacemaker. Said coil has an electronic circuit that enables recognition of the heartbeat and generation of the stimuli to the heart in synchronism with the "R" curve of the electrocardiogram.

State of the art

Defibrillator technology is based on that of pacemakers, which was invented some twenty years before. Precisely on account of the advantages obtained in the field of pacemakers, the defibrillator has been able to evolve with a surprising rapidity from 1980 to the present day.

The first implantation of a defibrillator in a human being was performed in 1980. Before then the patients affected by arrhythmias were treated with pharmacological therapy, which is able to reduce the incidence of arrhythmic phenomena, but not to interrupt them in the case where these arise.

The introduction of the implantable defibrillator in clinical practice has represented a fundamental passage in modern cardiosurgery. The technological evolution in this case has rendered possible an increase in the effectiveness of the instrument and the reduction of the invasiveness of the surgical intervention of implantation, which initially was very debilitating.

As compared to pharmacological therapy, the aspects to be considered are, on the one hand, the possibility of reducing the effects deriving from the toxicity of the drugs and, on the other, the period of post-operative convalescence. In the first implantations, proceeding to an operation as that of opening of the thorax, effected in total anaesthesia, with the need for intensive therapy subsequent to the operation, had of course a considerable impact on the times of recovery of the patient.

With the introduction of transvenous catheters and subsequently of endocardial implantation, the invasiveness of the intervention has obviously diminished: the times of recovery for the patient have shortened sensibly, thanks also to the lower incidence of complications.

Also the introduction of pectoral implantation has had a considerable impact on the organizational aspects of hospitals, which have adopted new-generation apparatuses. The post-operative stay in hospital is on average just two days. Consequently, as compared to

the past, resources such as personnel, equipment, and number of beds are more freely available.

There are moreover various aspects to be considered as regards costs: in fact, even though the initial cost of the device may seem high, therapy with implantable defibrillator has presented immediately a better cost-effectiveness ratio as compared to pharmacological therapy. The reason for this is that, as is highlighted by numerous studies, the rate of mortality in the latter case is higher than in the former.

The internal cardiac defibrillator (ICD) is usually constituted by a generator implanted subcutaneously and one or more electro-catheters positioned in the cardiac chambers, capable of detecting, interpreting, and storing the intrinsic electrical activity of the heart and, if need be, of supplying stimulations (antibradycardial therapy) or electric shocks (antitachycardial therapy).

The implantable cardiac defibrillator is the only device capable of recognizing a malignant ventricular tachyarrhythmia and of providing automatically an immediate electrical therapy in patients running the risk of sudden cardiac death. On the basis of the stimulation modalities, there may be distinguished single-chamber, dual-chamber, and biventricular (three-chamber) ICDs.

Single-chamber devices, which were the first to be launched on the market and are still in use, have a single electrode implanted in the right ventricle with functions of stimulation and registration (pacing/sensing) of the activity of a cardiac chamber.

Dual-chamber ICDs require the implantation of two electrodes, one in the atrium and one in the ventricle, and enable stimulation, analysis, and classification of both the ventricular rhythm and the atrial rhythm. The presence of an electrocatheter in the right atrium enables more precise classification of the cardiac rhythms and, in some models, also interruption of some forms of supraventricular tachycardia, such as for example atrial flutter.

The various models produced by the various manufacturers differ from one another substantially on the basis of programmability, algorithms and parameters of stimulation and of storage of data.

Biventricular ICDs unite in a single device a biventricular pacemaker and a defibrillator. The function of biventricular pacemaker is obtained through the insertion of an electrode in the coronary sinus capable of stimulating the left ventricle. In addition to the two standard electrodes present in the right atrium and ventricle, it enables atrial-ventricular re- synchronization and re-synchronization between the right ventricle and the left ventricle, with an improvement in the contractile function of the heart. These ICDs are indicated in the therapy of congestional cardiac decompensation.

In all cases of internal cardiac defibrillators, the problems that are encountered are due above all to the dimensions and weight of these devices, which are greater than those of a normal pacemaker, hi addition, they are particularly complex instruments capable of performing numerous control functions, which are automatic, are linked to internal management software, of extremely delicate application, and frequently take away from the doctor the possibility of intervention. Both factors consequently determine a considerable complexity of use and of immediate functionality. In addition, the coils that are used today for replacing the PM if this were to stop functioning, were to function badly or else during the operations of replacement of the PM, work in "asynchronism", i.e., they send pulses that are not synchronous with the point "R" of the curve of the heartbeat. Their use is hence not optimal for the heart and can serve only for limited periods.

The patent No. DE 698 30 203 describes in particular the technical implementation of the RF transmitter element, of the receiver element, as well as of the stimulation electrode. The coil is not an isolated implantable component, in so far as it is located within the receiving element coupled to a rectifier. All the components are then connected via the microcontroller to the electrode.

Now, the fact that, notwithstanding the constructional difference, the system of DI can presumably be brought back to the invention claimed by the present applicant, draws attention to the need to add to the definitions used in the independent claim a further

technical detail that may distinguish the present invention from the one described regarding the state of the art.

Aim of the invention

The main aim of the present invention is consequently to provide an implantable system of very small dimensions that will enable replacement of the PM offering a wider margin of time in use and ease of application.

Description of the invention

The problems listed above are solved by an implantable RF defibrillator according to

Claim 1. Further advantageous aspects are defined in the dependent claims.

For a better understanding of the subject of the present invention reference will be made to the attached Figures 1 — 3, wherein:

Figure 1 illustrates an implantable RF coil with stimulation electrode;

Figure 2 illustrates an external apparatus with RF output antenna; and

Figure 3 illustrates a coil fitted along the stimulation electrode of the pacemaker.

The implantable defibrillator according to the present invention consequently comprises:

- an implantable RF coil 10 equipped with a circuit 30 for generating the stimulation signal; and

- an external apparatus 2 with RF output antenna coupled to the coil 10 for transmission of the desired type of stimulation, where the coil is inserted together

with a detection and stimulation electrode 20 or else is fitted along the stimulation electrode of the pacemaker.

The coil is fitted on the electrode of the PM in the appropriate point of the thorax, generally on the opposite side to the PM, where it is possible to apply the antenna of the RF generator easily. Its functions remain the same: it replaces the PM when there is a technical problem or else at the moment of replacement of the PM. Said coil has an electronic circuit that enables recognition of the heartbeat and generates the stimuli to the heart in synchronism with the "R" curve of the electrocardiogram.

The other new idea of the present invention is that the RF generator will perform direct transmission on the coil so as to generate the current that sends the pulses to the electrode in the heart to stimulate it, without there being any need for batteries. The stimulation electrode is directed in the atrium for a low-energy defibrillation, of between 5 and 10 joule. The coil hence receives the energy transmitted by the external apparatus (Figure 2), reconstructing the modality of low-energy atrial defibrillation.

The reception coil 10 is equipped with a stimulation-signal-forming circuit 30, thanks to which said signal is sent to the stimulation electrode 20. RF stimulation synchronous with the "R" wave offered by this coil represents a solution of maximum safety for the patient.

The second, component is constituted by the external apparatus with RF output antenna 1, which can be coupled with the implanted one (Figure 1) to which it is possible to transmit the desired type of stimulation. The apparatus may set the functions that are deemed necessary so as to be able to execute interventions of atrial defibrillation.

The apparatus can operate either asynchronously or synchronously with the QRS signals detected on the patient. Said apparatus is also equipped with an input for ECG. In the development of this apparatus various features that might prove important may be added, such as Holter functions, display functions, functions of storage of the cardiac activity, etc.

Thanks to the present device, with the simple implantation of a coil with a stimulation electrode or directly on the stimulation electrode of the pacemaker, a universal instrument of intervention is provided, which is not perceived by the patient but has a wide application for the cardiologist, who may intervene and defibrillate the atrium in all cases in which a low-energy atrial defibrillation is able to solve a particular situation. It is consequently evident that this coil can be used either as direct stimulation or as alternative to stimulation by pacemaker, it being arranged so that it surrounds directly the electrode of the latter, moreover offering the advantage of the possibility of replacing the PM without being tied down to the limitation of time due to the use of batteries.