Bi-chamber stimulation coils for atrial defibrillation and ventricular stimulation

Field of the invention

The present invention relates to a defibrillator having an internal implantable component and an external coupled component equipped with output radio-frequency (RF) antenna. The internal component is equipped with two coils and two corresponding stimulation electrodes for enabling simultaneous stimulation or stimulation in sequence of the two cardiac chambers (atrium and ventricle).

State of the art

Defibrillator technology is based upon that of the pacemaker, 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 modem 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 drugs and, on the other, the period of post-operative convalescence.

hi 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 decreased: 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 the 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 by 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 the atrial- ventricular re-synchronization and re-synchronization between right ventricle and left ventricle, with an improvement in the contractile function of the heart. These ICDs are indicated in the therapy of congestional cardiac decompensation.

m all the cases of internal cardiac defibrillators, the problems that are encountered are due above all to the dimensions and weight of these devices, given that they are greater than those of a normal pacemaker, hi the case then where it is intended to stimulate

simultaneously the two cardiac chambers, the operative conditions are considerably complicated, both on account of the need to use two stimulation electrodes at the same time and on account of the risk of interference occurring between the RF signals with which said electrodes are governed. In addition, they are instruments that are particularly complex and 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. AU these factors consequently determine a considerable complexity of use and of immediate functionality.

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 atrial defibrillation and at the same time ventricular stimulation, without the two types of stimulation interfering with one another.

A second aim of the present invention is to provide a system for atrial and ventricular stimulation that will enable distinct management of the two types of stimulation.

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 and 2, wherein:

Figure 1 illustrates implantable RF coils with corresponding stimulation electrodes; and Figure 2 illustrates an external apparatus with RF output antenna.

The implantable defibrillator according to the present invention consequently comprises: - two implantable RF coils 10 equipped with a circuit for generating the stimulation signal, connected to each of which is a stimulation electrode 20; and

- an external apparatus 2 with single RF output antenna coupled to the coils 10 for transmission of the desired type of stimulation,

and is characterized in that each coil is set at a frequency that is different from that of the other coil so that activation of one will not create any signals or interference on the other, and moreover in that the external apparatus 2 has separate control means for managing each of the two coils independently such as to enable distinct atrial and ventricular stimulation. The stimulation electrode is directed in the atrium for a low-energy defibrillation, of between 5 and 10 joule. Said coils will receive the energy transmitted by the external apparatus (Figure 2), reconstructing the modality of low-energy atrial defibrillation.

Each reception coil 10 is equipped with a stimulation-signal-forming circuit, thanks to which said signal is sent to the corresponding stimulation electrode 20.

The second component is constituted by the external apparatus with RF output antenna that can be coupled with the implanted one (Figure 2) 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 and ventricular stimulation. Given that it is equipped with distinct controls 21, 22 for each of the coils, it is hence possible to govern each of them separately, without interference occurring between the two. 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.

As has been specified previously, the transmission antenna of the external apparatus is single and can transmit according to which chamber it is intended to stimulate.

It will thus be possible to stimulate the two cardiac chambers distinctly (atrium or ventricle) or stimulate them in sequence.

The external apparatus can also function in a way synchronizable with the ECG signal for those patients who have in any case a cardiac activity of their own or are carriers of

pacemakers, but above all can associate a ventricular stimulation to an atrial defibrillation with low level of energy so as to not to create any trauma to the cardiac cells.

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.